Separating bgwriter and checkpointer

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index e3dd472..f8027c1 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -315,6 +315,9 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			case BgWriterProcess:
 				statmsg = "writer process";
 				break;
+			case CheckpointerProcess:
+				statmsg = "checkpointer process";
+				break;
 			case WalWriterProcess:
 				statmsg = "wal writer process";
 				break;
@@ -419,6 +422,11 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			BackgroundWriterMain();
 			proc_exit(1);		/* should never return */
 
+		case CheckpointerProcess:
+			/* don't set signals, checkpointer has its own agenda */
+			CheckpointerMain();
+			proc_exit(1);		/* should never return */
+
 		case WalWriterProcess:
 			/* don't set signals, walwriter has its own agenda */
 			InitXLOGAccess();
diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 0767e97..e7414d2 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -13,6 +13,6 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = autovacuum.o bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o \
-	syslogger.o walwriter.o
+	syslogger.o walwriter.o checkpointer.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2d0b639..e0f3167 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -10,20 +10,13 @@
  * still empowered to issue writes if the bgwriter fails to maintain enough
  * clean shared buffers.
  *
- * The bgwriter is also charged with handling all checkpoints.	It will
- * automatically dispatch a checkpoint after a certain amount of time has
- * elapsed since the last one, and it can be signaled to perform requested
- * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
- * so many WAL segments is implemented by having backends signal the bgwriter
- * when they fill WAL segments; the bgwriter itself doesn't watch for the
- * condition.)
+ * As of Postgres 9.2 the bgwriter no longer handles checkpoints.
  *
  * The bgwriter is started by the postmaster as soon as the startup subprocess
  * finishes, or as soon as recovery begins if we are doing archive recovery.
  * It remains alive until the postmaster commands it to terminate.
- * Normal termination is by SIGUSR2, which instructs the bgwriter to execute
- * a shutdown checkpoint and then exit(0).	(All backends must be stopped
- * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
+ * Emergency termination is by SIGQUIT; like any
  * backend, the bgwriter will simply abort and exit on SIGQUIT.
  *
  * If the bgwriter exits unexpectedly, the postmaster treats that the same
@@ -54,7 +47,6 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
-#include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
@@ -67,96 +59,15 @@
 #include "utils/resowner.h"
 
 
-/*----------
- * Shared memory area for communication between bgwriter and backends
- *
- * The ckpt counters allow backends to watch for completion of a checkpoint
- * request they send.  Here's how it works:
- *	* At start of a checkpoint, bgwriter reads (and clears) the request flags
- *	  and increments ckpt_started, while holding ckpt_lck.
- *	* On completion of a checkpoint, bgwriter sets ckpt_done to
- *	  equal ckpt_started.
- *	* On failure of a checkpoint, bgwriter increments ckpt_failed
- *	  and sets ckpt_done to equal ckpt_started.
- *
- * The algorithm for backends is:
- *	1. Record current values of ckpt_failed and ckpt_started, and
- *	   set request flags, while holding ckpt_lck.
- *	2. Send signal to request checkpoint.
- *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
- *	   begun since you started this algorithm (although *not* that it was
- *	   specifically initiated by your signal), and that it is using your flags.
- *	4. Record new value of ckpt_started.
- *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
- *	   arithmetic here in case counters wrap around.)  Now you know a
- *	   checkpoint has started and completed, but not whether it was
- *	   successful.
- *	6. If ckpt_failed is different from the originally saved value,
- *	   assume request failed; otherwise it was definitely successful.
- *
- * ckpt_flags holds the OR of the checkpoint request flags sent by all
- * requesting backends since the last checkpoint start.  The flags are
- * chosen so that OR'ing is the correct way to combine multiple requests.
- *
- * num_backend_writes is used to count the number of buffer writes performed
- * by non-bgwriter processes.  This counter should be wide enough that it
- * can't overflow during a single bgwriter cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the background writer failed to absorb their request.
- *
- * The requests array holds fsync requests sent by backends and not yet
- * absorbed by the bgwriter.
- *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by BgWriterCommLock.
- *----------
- */
-typedef struct
-{
-	RelFileNodeBackend rnode;
-	ForkNumber	forknum;
-	BlockNumber segno;			/* see md.c for special values */
-	/* might add a real request-type field later; not needed yet */
-} BgWriterRequest;
-
-typedef struct
-{
-	pid_t		bgwriter_pid;	/* PID of bgwriter (0 if not started) */
-
-	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
-
-	int			ckpt_started;	/* advances when checkpoint starts */
-	int			ckpt_done;		/* advances when checkpoint done */
-	int			ckpt_failed;	/* advances when checkpoint fails */
-
-	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
-
-	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
-	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
-
-	int			num_requests;	/* current # of requests */
-	int			max_requests;	/* allocated array size */
-	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
-} BgWriterShmemStruct;
-
-static BgWriterShmemStruct *BgWriterShmem;
-
-/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
-#define WRITES_PER_ABSORB		1000
-
 /*
  * GUC parameters
  */
 int			BgWriterDelay = 200;
-int			CheckPointTimeout = 300;
-int			CheckPointWarning = 30;
-double		CheckPointCompletionTarget = 0.5;
 
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
 static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t checkpoint_requested = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -164,29 +75,14 @@ static volatile sig_atomic_t shutdown_requested = false;
  */
 static bool am_bg_writer = false;
 
-static bool ckpt_active = false;
-
-/* these values are valid when ckpt_active is true: */
-static pg_time_t ckpt_start_time;
-static XLogRecPtr ckpt_start_recptr;
-static double ckpt_cached_elapsed;
-
-static pg_time_t last_checkpoint_time;
-static pg_time_t last_xlog_switch_time;
-
 /* Prototypes for private functions */
 
-static void CheckArchiveTimeout(void);
 static void BgWriterNap(void);
-static bool IsCheckpointOnSchedule(double progress);
-static bool ImmediateCheckpointRequested(void);
-static bool CompactBgwriterRequestQueue(void);
 
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
 static void BgSigHupHandler(SIGNAL_ARGS);
-static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -202,7 +98,6 @@ BackgroundWriterMain(void)
 	sigjmp_buf	local_sigjmp_buf;
 	MemoryContext bgwriter_context;
 
-	BgWriterShmem->bgwriter_pid = MyProcPid;
 	am_bg_writer = true;
 
 	/*
@@ -228,8 +123,8 @@ BackgroundWriterMain(void)
 	 * process to participate in ProcSignal signalling.
 	 */
 	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
-	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
-	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
+	pqsignal(SIGINT, SIG_IGN);			/* as of 9.2 no longer requests checkpoint */
+	pqsignal(SIGTERM, SIG_IGN); 		/* ignore SIGTERM */
 	pqsignal(SIGQUIT, bg_quickdie);		/* hard crash time */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -249,11 +144,6 @@ BackgroundWriterMain(void)
 	sigdelset(&BlockSig, SIGQUIT);
 
 	/*
-	 * Initialize so that first time-driven event happens at the correct time.
-	 */
-	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
-
-	/*
 	 * Create a resource owner to keep track of our resources (currently only
 	 * buffer pins).
 	 */
@@ -305,20 +195,6 @@ BackgroundWriterMain(void)
 		AtEOXact_Files();
 		AtEOXact_HashTables(false);
 
-		/* Warn any waiting backends that the checkpoint failed. */
-		if (ckpt_active)
-		{
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_failed++;
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			ckpt_active = false;
-		}
-
 		/*
 		 * Now return to normal top-level context and clear ErrorContext for
 		 * next time.
@@ -361,19 +237,11 @@ BackgroundWriterMain(void)
 	if (RecoveryInProgress())
 		ThisTimeLineID = GetRecoveryTargetTLI();
 
-	/* Do this once before starting the loop, then just at SIGHUP time. */
-	SyncRepUpdateSyncStandbysDefined();
-
 	/*
 	 * Loop forever
 	 */
 	for (;;)
 	{
-		bool		do_checkpoint = false;
-		int			flags = 0;
-		pg_time_t	now;
-		int			elapsed_secs;
-
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -381,23 +249,11 @@ BackgroundWriterMain(void)
 		if (!PostmasterIsAlive())
 			exit(1);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		AbsorbFsyncRequests();
-
 		if (got_SIGHUP)
 		{
 			got_SIGHUP = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-		if (checkpoint_requested)
-		{
-			checkpoint_requested = false;
-			do_checkpoint = true;
-			BgWriterStats.m_requested_checkpoints++;
 		}
 		if (shutdown_requested)
 		{
@@ -406,142 +262,14 @@ BackgroundWriterMain(void)
 			 * control back to the sigsetjmp block above
 			 */
 			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
 			/* Normal exit from the bgwriter is here */
 			proc_exit(0);		/* done */
 		}
 
 		/*
-		 * Force a checkpoint if too much time has elapsed since the last one.
-		 * Note that we count a timed checkpoint in stats only when this
-		 * occurs without an external request, but we set the CAUSE_TIME flag
-		 * bit even if there is also an external request.
+		 * Do one cycle of dirty-buffer writing.
 		 */
-		now = (pg_time_t) time(NULL);
-		elapsed_secs = now - last_checkpoint_time;
-		if (elapsed_secs >= CheckPointTimeout)
-		{
-			if (!do_checkpoint)
-				BgWriterStats.m_timed_checkpoints++;
-			do_checkpoint = true;
-			flags |= CHECKPOINT_CAUSE_TIME;
-		}
-
-		/*
-		 * Do a checkpoint if requested, otherwise do one cycle of
-		 * dirty-buffer writing.
-		 */
-		if (do_checkpoint)
-		{
-			bool		ckpt_performed = false;
-			bool		do_restartpoint;
-
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			/*
-			 * Check if we should perform a checkpoint or a restartpoint. As a
-			 * side-effect, RecoveryInProgress() initializes TimeLineID if
-			 * it's not set yet.
-			 */
-			do_restartpoint = RecoveryInProgress();
-
-			/*
-			 * Atomically fetch the request flags to figure out what kind of a
-			 * checkpoint we should perform, and increase the started-counter
-			 * to acknowledge that we've started a new checkpoint.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			flags |= bgs->ckpt_flags;
-			bgs->ckpt_flags = 0;
-			bgs->ckpt_started++;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			/*
-			 * The end-of-recovery checkpoint is a real checkpoint that's
-			 * performed while we're still in recovery.
-			 */
-			if (flags & CHECKPOINT_END_OF_RECOVERY)
-				do_restartpoint = false;
-
-			/*
-			 * We will warn if (a) too soon since last checkpoint (whatever
-			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
-			 * since the last checkpoint start.  Note in particular that this
-			 * implementation will not generate warnings caused by
-			 * CheckPointTimeout < CheckPointWarning.
-			 */
-			if (!do_restartpoint &&
-				(flags & CHECKPOINT_CAUSE_XLOG) &&
-				elapsed_secs < CheckPointWarning)
-				ereport(LOG,
-						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
-				"checkpoints are occurring too frequently (%d seconds apart)",
-									   elapsed_secs,
-									   elapsed_secs),
-						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
-
-			/*
-			 * Initialize bgwriter-private variables used during checkpoint.
-			 */
-			ckpt_active = true;
-			if (!do_restartpoint)
-				ckpt_start_recptr = GetInsertRecPtr();
-			ckpt_start_time = now;
-			ckpt_cached_elapsed = 0;
-
-			/*
-			 * Do the checkpoint.
-			 */
-			if (!do_restartpoint)
-			{
-				CreateCheckPoint(flags);
-				ckpt_performed = true;
-			}
-			else
-				ckpt_performed = CreateRestartPoint(flags);
-
-			/*
-			 * After any checkpoint, close all smgr files.	This is so we
-			 * won't hang onto smgr references to deleted files indefinitely.
-			 */
-			smgrcloseall();
-
-			/*
-			 * Indicate checkpoint completion to any waiting backends.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (ckpt_performed)
-			{
-				/*
-				 * Note we record the checkpoint start time not end time as
-				 * last_checkpoint_time.  This is so that time-driven
-				 * checkpoints happen at a predictable spacing.
-				 */
-				last_checkpoint_time = now;
-			}
-			else
-			{
-				/*
-				 * We were not able to perform the restartpoint (checkpoints
-				 * throw an ERROR in case of error).  Most likely because we
-				 * have not received any new checkpoint WAL records since the
-				 * last restartpoint. Try again in 15 s.
-				 */
-				last_checkpoint_time = now - CheckPointTimeout + 15;
-			}
-
-			ckpt_active = false;
-		}
-		else
-			BgBufferSync();
-
-		/* Check for archive_timeout and switch xlog files if necessary. */
-		CheckArchiveTimeout();
+		BgBufferSync();
 
 		/* Nap for the configured time. */
 		BgWriterNap();
@@ -549,61 +277,6 @@ BackgroundWriterMain(void)
 }
 
 /*
- * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
- *
- * This will switch to a new WAL file and force an archive file write
- * if any activity is recorded in the current WAL file, including just
- * a single checkpoint record.
- */
-static void
-CheckArchiveTimeout(void)
-{
-	pg_time_t	now;
-	pg_time_t	last_time;
-
-	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
-		return;
-
-	now = (pg_time_t) time(NULL);
-
-	/* First we do a quick check using possibly-stale local state. */
-	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
-		return;
-
-	/*
-	 * Update local state ... note that last_xlog_switch_time is the last time
-	 * a switch was performed *or requested*.
-	 */
-	last_time = GetLastSegSwitchTime();
-
-	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
-
-	/* Now we can do the real check */
-	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
-	{
-		XLogRecPtr	switchpoint;
-
-		/* OK, it's time to switch */
-		switchpoint = RequestXLogSwitch();
-
-		/*
-		 * If the returned pointer points exactly to a segment boundary,
-		 * assume nothing happened.
-		 */
-		if ((switchpoint.xrecoff % XLogSegSize) != 0)
-			ereport(DEBUG1,
-				(errmsg("transaction log switch forced (archive_timeout=%d)",
-						XLogArchiveTimeout)));
-
-		/*
-		 * Update state in any case, so we don't retry constantly when the
-		 * system is idle.
-		 */
-		last_xlog_switch_time = now;
-	}
-}
-
-/*
  * BgWriterNap -- Nap for the configured time or until a signal is received.
  */
 static void
@@ -624,185 +297,24 @@ BgWriterNap(void)
 	 * respond reasonably promptly when someone signals us, break down the
 	 * sleep into 1-second increments, and check for interrupts after each
 	 * nap.
-	 *
-	 * We absorb pending requests after each short sleep.
 	 */
-	if (bgwriter_lru_maxpages > 0 || ckpt_active)
+	if (bgwriter_lru_maxpages > 0)
 		udelay = BgWriterDelay * 1000L;
-	else if (XLogArchiveTimeout > 0)
-		udelay = 1000000L;		/* One second */
 	else
 		udelay = 10000000L;		/* Ten seconds */
 
 	while (udelay > 999999L)
 	{
-		if (got_SIGHUP || shutdown_requested ||
-		(ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested))
+		if (got_SIGHUP || shutdown_requested)
 			break;
 		pg_usleep(1000000L);
-		AbsorbFsyncRequests();
 		udelay -= 1000000L;
 	}
 
-	if (!(got_SIGHUP || shutdown_requested ||
-	  (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested)))
+	if (!(got_SIGHUP || shutdown_requested))
 		pg_usleep(udelay);
 }
 
-/*
- * Returns true if an immediate checkpoint request is pending.	(Note that
- * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
- * there is one pending behind it.)
- */
-static bool
-ImmediateCheckpointRequested(void)
-{
-	if (checkpoint_requested)
-	{
-		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-		/*
-		 * We don't need to acquire the ckpt_lck in this case because we're
-		 * only looking at a single flag bit.
-		 */
-		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
-			return true;
-	}
-	return false;
-}
-
-/*
- * CheckpointWriteDelay -- yield control to bgwriter during a checkpoint
- *
- * This function is called after each page write performed by BufferSync().
- * It is responsible for keeping the bgwriter's normal activities in
- * progress during a long checkpoint, and for throttling BufferSync()'s
- * write rate to hit checkpoint_completion_target.
- *
- * The checkpoint request flags should be passed in; currently the only one
- * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
- *
- * 'progress' is an estimate of how much of the work has been done, as a
- * fraction between 0.0 meaning none, and 1.0 meaning all done.
- */
-void
-CheckpointWriteDelay(int flags, double progress)
-{
-	static int	absorb_counter = WRITES_PER_ABSORB;
-
-	/* Do nothing if checkpoint is being executed by non-bgwriter process */
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * Perform the usual bgwriter duties and take a nap, unless we're behind
-	 * schedule, in which case we just try to catch up as quickly as possible.
-	 */
-	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
-		!ImmediateCheckpointRequested() &&
-		IsCheckpointOnSchedule(progress))
-	{
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-
-		BgBufferSync();
-		CheckArchiveTimeout();
-		BgWriterNap();
-	}
-	else if (--absorb_counter <= 0)
-	{
-		/*
-		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
-		 * operations even when we don't sleep, to prevent overflow of the
-		 * fsync request queue.
-		 */
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-	}
-}
-
-/*
- * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
- *		 in time?
- *
- * Compares the current progress against the time/segments elapsed since last
- * checkpoint, and returns true if the progress we've made this far is greater
- * than the elapsed time/segments.
- */
-static bool
-IsCheckpointOnSchedule(double progress)
-{
-	XLogRecPtr	recptr;
-	struct timeval now;
-	double		elapsed_xlogs,
-				elapsed_time;
-
-	Assert(ckpt_active);
-
-	/* Scale progress according to checkpoint_completion_target. */
-	progress *= CheckPointCompletionTarget;
-
-	/*
-	 * Check against the cached value first. Only do the more expensive
-	 * calculations once we reach the target previously calculated. Since
-	 * neither time or WAL insert pointer moves backwards, a freshly
-	 * calculated value can only be greater than or equal to the cached value.
-	 */
-	if (progress < ckpt_cached_elapsed)
-		return false;
-
-	/*
-	 * Check progress against WAL segments written and checkpoint_segments.
-	 *
-	 * We compare the current WAL insert location against the location
-	 * computed before calling CreateCheckPoint. The code in XLogInsert that
-	 * actually triggers a checkpoint when checkpoint_segments is exceeded
-	 * compares against RedoRecptr, so this is not completely accurate.
-	 * However, it's good enough for our purposes, we're only calculating an
-	 * estimate anyway.
-	 */
-	if (!RecoveryInProgress())
-	{
-		recptr = GetInsertRecPtr();
-		elapsed_xlogs =
-			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
-			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
-			CheckPointSegments;
-
-		if (progress < elapsed_xlogs)
-		{
-			ckpt_cached_elapsed = elapsed_xlogs;
-			return false;
-		}
-	}
-
-	/*
-	 * Check progress against time elapsed and checkpoint_timeout.
-	 */
-	gettimeofday(&now, NULL);
-	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
-					now.tv_usec / 1000000.0) / CheckPointTimeout;
-
-	if (progress < elapsed_time)
-	{
-		ckpt_cached_elapsed = elapsed_time;
-		return false;
-	}
-
-	/* It looks like we're on schedule. */
-	return true;
-}
-
-
 /* --------------------------------
  *		signal handler routines
  * --------------------------------
@@ -847,441 +359,9 @@ BgSigHupHandler(SIGNAL_ARGS)
 	got_SIGHUP = true;
 }
 
-/* SIGINT: set flag to run a normal checkpoint right away */
-static void
-ReqCheckpointHandler(SIGNAL_ARGS)
-{
-	checkpoint_requested = true;
-}
-
 /* SIGUSR2: set flag to run a shutdown checkpoint and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
 }
-
-
-/* --------------------------------
- *		communication with backends
- * --------------------------------
- */
-
-/*
- * BgWriterShmemSize
- *		Compute space needed for bgwriter-related shared memory
- */
-Size
-BgWriterShmemSize(void)
-{
-	Size		size;
-
-	/*
-	 * Currently, the size of the requests[] array is arbitrarily set equal to
-	 * NBuffers.  This may prove too large or small ...
-	 */
-	size = offsetof(BgWriterShmemStruct, requests);
-	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
-
-	return size;
-}
-
-/*
- * BgWriterShmemInit
- *		Allocate and initialize bgwriter-related shared memory
- */
-void
-BgWriterShmemInit(void)
-{
-	bool		found;
-
-	BgWriterShmem = (BgWriterShmemStruct *)
-		ShmemInitStruct("Background Writer Data",
-						BgWriterShmemSize(),
-						&found);
-
-	if (!found)
-	{
-		/* First time through, so initialize */
-		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
-		SpinLockInit(&BgWriterShmem->ckpt_lck);
-		BgWriterShmem->max_requests = NBuffers;
-	}
-}
-
-/*
- * RequestCheckpoint
- *		Called in backend processes to request a checkpoint
- *
- * flags is a bitwise OR of the following:
- *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
- *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
- *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
- *		ignoring checkpoint_completion_target parameter.
- *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
- *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
- *		CHECKPOINT_END_OF_RECOVERY).
- *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
- *		just signal bgwriter to do it, and return).
- *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
- *		(This affects logging, and in particular enables CheckPointWarning.)
- */
-void
-RequestCheckpoint(int flags)
-{
-	/* use volatile pointer to prevent code rearrangement */
-	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-	int			ntries;
-	int			old_failed,
-				old_started;
-
-	/*
-	 * If in a standalone backend, just do it ourselves.
-	 */
-	if (!IsPostmasterEnvironment)
-	{
-		/*
-		 * There's no point in doing slow checkpoints in a standalone backend,
-		 * because there's no other backends the checkpoint could disrupt.
-		 */
-		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
-
-		/*
-		 * After any checkpoint, close all smgr files.	This is so we won't
-		 * hang onto smgr references to deleted files indefinitely.
-		 */
-		smgrcloseall();
-
-		return;
-	}
-
-	/*
-	 * Atomically set the request flags, and take a snapshot of the counters.
-	 * When we see ckpt_started > old_started, we know the flags we set here
-	 * have been seen by bgwriter.
-	 *
-	 * Note that we OR the flags with any existing flags, to avoid overriding
-	 * a "stronger" request by another backend.  The flag senses must be
-	 * chosen to make this work!
-	 */
-	SpinLockAcquire(&bgs->ckpt_lck);
-
-	old_failed = bgs->ckpt_failed;
-	old_started = bgs->ckpt_started;
-	bgs->ckpt_flags |= flags;
-
-	SpinLockRelease(&bgs->ckpt_lck);
-
-	/*
-	 * Send signal to request checkpoint.  It's possible that the bgwriter
-	 * hasn't started yet, or is in process of restarting, so we will retry a
-	 * few times if needed.  Also, if not told to wait for the checkpoint to
-	 * occur, we consider failure to send the signal to be nonfatal and merely
-	 * LOG it.
-	 */
-	for (ntries = 0;; ntries++)
-	{
-		if (BgWriterShmem->bgwriter_pid == 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-				"could not request checkpoint because bgwriter not running");
-				break;
-			}
-		}
-		else if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-					 "could not signal for checkpoint: %m");
-				break;
-			}
-		}
-		else
-			break;				/* signal sent successfully */
-
-		CHECK_FOR_INTERRUPTS();
-		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
-	}
-
-	/*
-	 * If requested, wait for completion.  We detect completion according to
-	 * the algorithm given above.
-	 */
-	if (flags & CHECKPOINT_WAIT)
-	{
-		int			new_started,
-					new_failed;
-
-		/* Wait for a new checkpoint to start. */
-		for (;;)
-		{
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_started = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_started != old_started)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		/*
-		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
-		 */
-		for (;;)
-		{
-			int			new_done;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_done = bgs->ckpt_done;
-			new_failed = bgs->ckpt_failed;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_done - new_started >= 0)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		if (new_failed != old_failed)
-			ereport(ERROR,
-					(errmsg("checkpoint request failed"),
-					 errhint("Consult recent messages in the server log for details.")));
-	}
-}
-
-/*
- * ForwardFsyncRequest
- *		Forward a file-fsync request from a backend to the bgwriter
- *
- * Whenever a backend is compelled to write directly to a relation
- * (which should be seldom, if the bgwriter is getting its job done),
- * the backend calls this routine to pass over knowledge that the relation
- * is dirty and must be fsync'd before next checkpoint.  We also use this
- * opportunity to count such writes for statistical purposes.
- *
- * segno specifies which segment (not block!) of the relation needs to be
- * fsync'd.  (Since the valid range is much less than BlockNumber, we can
- * use high values for special flags; that's all internal to md.c, which
- * see for details.)
- *
- * To avoid holding the lock for longer than necessary, we normally write
- * to the requests[] queue without checking for duplicates.  The bgwriter
- * will have to eliminate dups internally anyway.  However, if we discover
- * that the queue is full, we make a pass over the entire queue to compact
- * it.	This is somewhat expensive, but the alternative is for the backend
- * to perform its own fsync, which is far more expensive in practice.  It
- * is theoretically possible a backend fsync might still be necessary, if
- * the queue is full and contains no duplicate entries.  In that case, we
- * let the backend know by returning false.
- */
-bool
-ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
-					BlockNumber segno)
-{
-	BgWriterRequest *request;
-
-	if (!IsUnderPostmaster)
-		return false;			/* probably shouldn't even get here */
-
-	if (am_bg_writer)
-		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
-
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Count all backend writes regardless of if they fit in the queue */
-	BgWriterShmem->num_backend_writes++;
-
-	/*
-	 * If the background writer isn't running or the request queue is full,
-	 * the backend will have to perform its own fsync request.	But before
-	 * forcing that to happen, we can try to compact the background writer
-	 * request queue.
-	 */
-	if (BgWriterShmem->bgwriter_pid == 0 ||
-		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
-		 && !CompactBgwriterRequestQueue()))
-	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		BgWriterShmem->num_backend_fsync++;
-		LWLockRelease(BgWriterCommLock);
-		return false;
-	}
-	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
-	request->rnode = rnode;
-	request->forknum = forknum;
-	request->segno = segno;
-	LWLockRelease(BgWriterCommLock);
-	return true;
-}
-
-/*
- * CompactBgwriterRequestQueue
- *		Remove duplicates from the request queue to avoid backend fsyncs.
- *
- * Although a full fsync request queue is not common, it can lead to severe
- * performance problems when it does happen.  So far, this situation has
- * only been observed to occur when the system is under heavy write load,
- * and especially during the "sync" phase of a checkpoint.	Without this
- * logic, each backend begins doing an fsync for every block written, which
- * gets very expensive and can slow down the whole system.
- *
- * Trying to do this every time the queue is full could lose if there
- * aren't any removable entries.  But should be vanishingly rare in
- * practice: there's one queue entry per shared buffer.
- */
-static bool
-CompactBgwriterRequestQueue()
-{
-	struct BgWriterSlotMapping
-	{
-		BgWriterRequest request;
-		int			slot;
-	};
-
-	int			n,
-				preserve_count;
-	int			num_skipped = 0;
-	HASHCTL		ctl;
-	HTAB	   *htab;
-	bool	   *skip_slot;
-
-	/* must hold BgWriterCommLock in exclusive mode */
-	Assert(LWLockHeldByMe(BgWriterCommLock));
-
-	/* Initialize temporary hash table */
-	MemSet(&ctl, 0, sizeof(ctl));
-	ctl.keysize = sizeof(BgWriterRequest);
-	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
-	ctl.hash = tag_hash;
-	htab = hash_create("CompactBgwriterRequestQueue",
-					   BgWriterShmem->num_requests,
-					   &ctl,
-					   HASH_ELEM | HASH_FUNCTION);
-
-	/* Initialize skip_slot array */
-	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
-
-	/*
-	 * The basic idea here is that a request can be skipped if it's followed
-	 * by a later, identical request.  It might seem more sensible to work
-	 * backwards from the end of the queue and check whether a request is
-	 * *preceded* by an earlier, identical request, in the hopes of doing less
-	 * copying.  But that might change the semantics, if there's an
-	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
-	 * we do it this way.  It would be possible to be even smarter if we made
-	 * the code below understand the specific semantics of such requests (it
-	 * could blow away preceding entries that would end up being canceled
-	 * anyhow), but it's not clear that the extra complexity would buy us
-	 * anything.
-	 */
-	for (n = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		BgWriterRequest *request;
-		struct BgWriterSlotMapping *slotmap;
-		bool		found;
-
-		request = &BgWriterShmem->requests[n];
-		slotmap = hash_search(htab, request, HASH_ENTER, &found);
-		if (found)
-		{
-			skip_slot[slotmap->slot] = true;
-			++num_skipped;
-		}
-		slotmap->slot = n;
-	}
-
-	/* Done with the hash table. */
-	hash_destroy(htab);
-
-	/* If no duplicates, we're out of luck. */
-	if (!num_skipped)
-	{
-		pfree(skip_slot);
-		return false;
-	}
-
-	/* We found some duplicates; remove them. */
-	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		if (skip_slot[n])
-			continue;
-		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
-	}
-	ereport(DEBUG1,
-	   (errmsg("compacted fsync request queue from %d entries to %d entries",
-			   BgWriterShmem->num_requests, preserve_count)));
-	BgWriterShmem->num_requests = preserve_count;
-
-	/* Cleanup. */
-	pfree(skip_slot);
-	return true;
-}
-
-/*
- * AbsorbFsyncRequests
- *		Retrieve queued fsync requests and pass them to local smgr.
- *
- * This is exported because it must be called during CreateCheckPoint;
- * we have to be sure we have accepted all pending requests just before
- * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
- * non-bgwriter processes, do nothing if not bgwriter.
- */
-void
-AbsorbFsyncRequests(void)
-{
-	BgWriterRequest *requests = NULL;
-	BgWriterRequest *request;
-	int			n;
-
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * We have to PANIC if we fail to absorb all the pending requests (eg,
-	 * because our hashtable runs out of memory).  This is because the system
-	 * cannot run safely if we are unable to fsync what we have been told to
-	 * fsync.  Fortunately, the hashtable is so small that the problem is
-	 * quite unlikely to arise in practice.
-	 */
-	START_CRIT_SECTION();
-
-	/*
-	 * We try to avoid holding the lock for a long time by copying the request
-	 * array.
-	 */
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Transfer write count into pending pgstats message */
-	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
-	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
-
-	BgWriterShmem->num_backend_writes = 0;
-	BgWriterShmem->num_backend_fsync = 0;
-
-	n = BgWriterShmem->num_requests;
-	if (n > 0)
-	{
-		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
-		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
-	}
-	BgWriterShmem->num_requests = 0;
-
-	LWLockRelease(BgWriterCommLock);
-
-	for (request = requests; n > 0; request++, n--)
-		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
-
-	if (requests)
-		pfree(requests);
-
-	END_CRIT_SECTION();
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
new file mode 100644
index 0000000..0ba83bb
--- /dev/null
+++ b/src/backend/postmaster/checkpointer.c
@@ -0,0 +1,1229 @@
+/*-------------------------------------------------------------------------
+ *
+ * checkpointer.c
+ *
+ * The checkpointer is new as of Postgres 9.2.	It handles all checkpoints.
+ * Checkpoints are automatically dispatched after a certain amount of time has
+ * elapsed since the last one, and it can be signaled to perform requested
+ * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
+ * so many WAL segments is implemented by having backends signal when they
+ * fill WAL segments; the checkpointer itself doesn't watch for the
+ * condition.)
+ *
+ * The checkpointer is started by the postmaster as soon as the startup subprocess
+ * finishes, or as soon as recovery begins if we are doing archive recovery.
+ * It remains alive until the postmaster commands it to terminate.
+ * Normal termination is by SIGUSR2, which instructs the checkpointer to execute
+ * a shutdown checkpoint and then exit(0).	(All backends must be stopped
+ * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * backend, the checkpointer will simply abort and exit on SIGQUIT.
+ *
+ * If the checkpointer exits unexpectedly, the postmaster treats that the same
+ * as a backend crash: shared memory may be corrupted, so remaining backends
+ * should be killed by SIGQUIT and then a recovery cycle started.  (Even if
+ * shared memory isn't corrupted, we have lost information about which
+ * files need to be fsync'd for the next checkpoint, and so a system
+ * restart needs to be forced.)
+ *
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/checkpointer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <signal.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "access/xlog_internal.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgwriter.h"
+#include "replication/syncrep.h"
+#include "storage/bufmgr.h"
+#include "storage/ipc.h"
+#include "storage/lwlock.h"
+#include "storage/pmsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+
+/*----------
+ * Shared memory area for communication between checkpointer and backends
+ *
+ * The ckpt counters allow backends to watch for completion of a checkpoint
+ * request they send.  Here's how it works:
+ *	* At start of a checkpoint, checkpointer reads (and clears) the request flags
+ *	  and increments ckpt_started, while holding ckpt_lck.
+ *	* On completion of a checkpoint, checkpointer sets ckpt_done to
+ *	  equal ckpt_started.
+ *	* On failure of a checkpoint, checkpointer increments ckpt_failed
+ *	  and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ *	1. Record current values of ckpt_failed and ckpt_started, and
+ *	   set request flags, while holding ckpt_lck.
+ *	2. Send signal to request checkpoint.
+ *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
+ *	   begun since you started this algorithm (although *not* that it was
+ *	   specifically initiated by your signal), and that it is using your flags.
+ *	4. Record new value of ckpt_started.
+ *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
+ *	   arithmetic here in case counters wrap around.)  Now you know a
+ *	   checkpoint has started and completed, but not whether it was
+ *	   successful.
+ *	6. If ckpt_failed is different from the originally saved value,
+ *	   assume request failed; otherwise it was definitely successful.
+ *
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start.  The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by non-bgwriter processes.  This counter should be wide enough that it
+ * can't overflow during a single bgwriter cycle.  num_backend_fsync
+ * counts the subset of those writes that also had to do their own fsync,
+ * because the background writer failed to absorb their request.
+ *
+ * The requests array holds fsync requests sent by backends and not yet
+ * absorbed by the checkpointer.
+ *
+ * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
+ * the requests fields are protected by BgWriterCommLock.
+ *----------
+ */
+typedef struct
+{
+	RelFileNodeBackend rnode;
+	ForkNumber	forknum;
+	BlockNumber segno;			/* see md.c for special values */
+	/* might add a real request-type field later; not needed yet */
+} BgWriterRequest;
+
+typedef struct
+{
+	pid_t		checkpointer_pid;	/* PID of bgwriter (0 if not started) */
+
+	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
+
+	int			ckpt_started;	/* advances when checkpoint starts */
+	int			ckpt_done;		/* advances when checkpoint done */
+	int			ckpt_failed;	/* advances when checkpoint fails */
+
+	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
+
+	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
+	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
+
+	int			num_requests;	/* current # of requests */
+	int			max_requests;	/* allocated array size */
+	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
+} BgWriterShmemStruct;
+
+static BgWriterShmemStruct *BgWriterShmem;
+
+/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB		1000
+
+/*
+ * GUC parameters
+ */
+int			CheckPointTimeout = 300;
+int			CheckPointWarning = 30;
+double		CheckPointCompletionTarget = 0.5;
+
+/*
+ * Flags set by interrupt handlers for later service in the main loop.
+ */
+static volatile sig_atomic_t got_SIGHUP = false;
+static volatile sig_atomic_t checkpoint_requested = false;
+static volatile sig_atomic_t shutdown_requested = false;
+
+/*
+ * Private state
+ */
+static bool am_checkpointer = false;
+
+static bool ckpt_active = false;
+
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void CheckArchiveTimeout(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+static bool CompactCheckpointerRequestQueue(void);
+
+/* Signal handlers */
+
+static void chkpt_quickdie(SIGNAL_ARGS);
+static void ChkptSigHupHandler(SIGNAL_ARGS);
+static void ReqCheckpointHandler(SIGNAL_ARGS);
+static void ReqShutdownHandler(SIGNAL_ARGS);
+
+
+/*
+ * Main entry point for checkpointer process
+ *
+ * This is invoked from BootstrapMain, which has already created the basic
+ * execution environment, but not enabled signals yet.
+ */
+void
+CheckpointerMain(void)
+{
+	sigjmp_buf	local_sigjmp_buf;
+	MemoryContext checkpointer_context;
+
+	BgWriterShmem->checkpointer_pid = MyProcPid;
+	am_checkpointer = true;
+
+	/*
+	 * If possible, make this process a group leader, so that the postmaster
+	 * can signal any child processes too.	(checkpointer probably never has any
+	 * child processes, but for consistency we make all postmaster child
+	 * processes do this.)
+	 */
+#ifdef HAVE_SETSID
+	if (setsid() < 0)
+		elog(FATAL, "setsid() failed: %m");
+#endif
+
+	/*
+	 * Properly accept or ignore signals the postmaster might send us
+	 *
+	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
+	 * system shutdown cycle, init will SIGTERM all processes at once.	We
+	 * want to wait for the backends to exit, whereupon the postmaster will
+	 * tell us it's okay to shut down (via SIGUSR2).
+	 *
+	 * SIGUSR1 is presently unused; keep it spare in case someday we want this
+	 * process to participate in ProcSignal signalling.
+	 */
+	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGINT, ReqCheckpointHandler);	/* request checkpoint */
+	pqsignal(SIGTERM, SIG_IGN);				/* ignore SIGTERM */
+	pqsignal(SIGQUIT, chkpt_quickdie);		/* hard crash time */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
+	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */
+
+	/*
+	 * Reset some signals that are accepted by postmaster but not here
+	 */
+	pqsignal(SIGCHLD, SIG_DFL);
+	pqsignal(SIGTTIN, SIG_DFL);
+	pqsignal(SIGTTOU, SIG_DFL);
+	pqsignal(SIGCONT, SIG_DFL);
+	pqsignal(SIGWINCH, SIG_DFL);
+
+	/* We allow SIGQUIT (quickdie) at all times */
+	sigdelset(&BlockSig, SIGQUIT);
+
+	/*
+	 * Initialize so that first time-driven event happens at the correct time.
+	 */
+	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
+
+	/*
+	 * Create a resource owner to keep track of our resources (currently only
+	 * buffer pins).
+	 */
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer");
+
+	/*
+	 * Create a memory context that we will do all our work in.  We do this so
+	 * that we can reset the context during error recovery and thereby avoid
+	 * possible memory leaks.  Formerly this code just ran in
+	 * TopMemoryContext, but resetting that would be a really bad idea.
+	 */
+	checkpointer_context = AllocSetContextCreate(TopMemoryContext,
+											 "Checkpointer",
+											 ALLOCSET_DEFAULT_MINSIZE,
+											 ALLOCSET_DEFAULT_INITSIZE,
+											 ALLOCSET_DEFAULT_MAXSIZE);
+	MemoryContextSwitchTo(checkpointer_context);
+
+	/*
+	 * If an exception is encountered, processing resumes here.
+	 *
+	 * See notes in postgres.c about the design of this coding.
+	 */
+	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
+	{
+		/* Since not using PG_TRY, must reset error stack by hand */
+		error_context_stack = NULL;
+
+		/* Prevent interrupts while cleaning up */
+		HOLD_INTERRUPTS();
+
+		/* Report the error to the server log */
+		EmitErrorReport();
+
+		/*
+		 * These operations are really just a minimal subset of
+		 * AbortTransaction().	We don't have very many resources to worry
+		 * about in checkpointer, but we do have LWLocks, buffers, and temp files.
+		 */
+		LWLockReleaseAll();
+		AbortBufferIO();
+		UnlockBuffers();
+		/* buffer pins are released here: */
+		ResourceOwnerRelease(CurrentResourceOwner,
+							 RESOURCE_RELEASE_BEFORE_LOCKS,
+							 false, true);
+		/* we needn't bother with the other ResourceOwnerRelease phases */
+		AtEOXact_Buffers(false);
+		AtEOXact_Files();
+		AtEOXact_HashTables(false);
+
+		/* Warn any waiting backends that the checkpoint failed. */
+		if (ckpt_active)
+		{
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_failed++;
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Now return to normal top-level context and clear ErrorContext for
+		 * next time.
+		 */
+		MemoryContextSwitchTo(checkpointer_context);
+		FlushErrorState();
+
+		/* Flush any leaked data in the top-level context */
+		MemoryContextResetAndDeleteChildren(checkpointer_context);
+
+		/* Now we can allow interrupts again */
+		RESUME_INTERRUPTS();
+
+		/*
+		 * Sleep at least 1 second after any error.  A write error is likely
+		 * to be repeated, and we don't want to be filling the error logs as
+		 * fast as we can.
+		 */
+		pg_usleep(1000000L);
+
+		/*
+		 * Close all open files after any error.  This is helpful on Windows,
+		 * where holding deleted files open causes various strange errors.
+		 * It's not clear we need it elsewhere, but shouldn't hurt.
+		 */
+		smgrcloseall();
+	}
+
+	/* We can now handle ereport(ERROR) */
+	PG_exception_stack = &local_sigjmp_buf;
+
+	/*
+	 * Unblock signals (they were blocked when the postmaster forked us)
+	 */
+	PG_SETMASK(&UnBlockSig);
+
+	/*
+	 * Use the recovery target timeline ID during recovery
+	 */
+	if (RecoveryInProgress())
+		ThisTimeLineID = GetRecoveryTargetTLI();
+
+	/* Do this once before starting the loop, then just at SIGHUP time. */
+	SyncRepUpdateSyncStandbysDefined();
+
+	/*
+	 * Loop forever
+	 */
+	for (;;)
+	{
+		bool		do_checkpoint = false;
+		int			flags = 0;
+		pg_time_t	now;
+		int			elapsed_secs;
+
+		/*
+		 * Emergency bailout if postmaster has died.  This is to avoid the
+		 * necessity for manual cleanup of all postmaster children.
+		 */
+		if (!PostmasterIsAlive())
+			exit(1);
+
+		/*
+		 * Process any requests or signals received recently.
+		 */
+		AbsorbFsyncRequests();
+
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+		if (checkpoint_requested)
+		{
+			checkpoint_requested = false;
+			do_checkpoint = true;
+			BgWriterStats.m_requested_checkpoints++;
+		}
+		if (shutdown_requested)
+		{
+			/*
+			 * From here on, elog(ERROR) should end with exit(1), not send
+			 * control back to the sigsetjmp block above
+			 */
+			ExitOnAnyError = true;
+			/* Close down the database */
+			ShutdownXLOG(0, 0);
+			/* Normal exit from the checkpointer is here */
+			proc_exit(0);		/* done */
+		}
+
+		/*
+		 * Force a checkpoint if too much time has elapsed since the last one.
+		 * Note that we count a timed checkpoint in stats only when this
+		 * occurs without an external request, but we set the CAUSE_TIME flag
+		 * bit even if there is also an external request.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+		{
+			if (!do_checkpoint)
+				BgWriterStats.m_timed_checkpoints++;
+			do_checkpoint = true;
+			flags |= CHECKPOINT_CAUSE_TIME;
+		}
+
+		/*
+		 * Do a checkpoint if requested.
+		 */
+		if (do_checkpoint)
+		{
+			bool		ckpt_performed = false;
+			bool		do_restartpoint;
+
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			/*
+			 * Check if we should perform a checkpoint or a restartpoint. As a
+			 * side-effect, RecoveryInProgress() initializes TimeLineID if
+			 * it's not set yet.
+			 */
+			do_restartpoint = RecoveryInProgress();
+
+			/*
+			 * Atomically fetch the request flags to figure out what kind of a
+			 * checkpoint we should perform, and increase the started-counter
+			 * to acknowledge that we've started a new checkpoint.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			flags |= bgs->ckpt_flags;
+			bgs->ckpt_flags = 0;
+			bgs->ckpt_started++;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			/*
+			 * The end-of-recovery checkpoint is a real checkpoint that's
+			 * performed while we're still in recovery.
+			 */
+			if (flags & CHECKPOINT_END_OF_RECOVERY)
+				do_restartpoint = false;
+
+			/*
+			 * We will warn if (a) too soon since last checkpoint (whatever
+			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+			 * since the last checkpoint start.  Note in particular that this
+			 * implementation will not generate warnings caused by
+			 * CheckPointTimeout < CheckPointWarning.
+			 */
+			if (!do_restartpoint &&
+				(flags & CHECKPOINT_CAUSE_XLOG) &&
+				elapsed_secs < CheckPointWarning)
+				ereport(LOG,
+						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+				"checkpoints are occurring too frequently (%d seconds apart)",
+									   elapsed_secs,
+									   elapsed_secs),
+						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
+
+			/*
+			 * Initialize checkpointer-private variables used during checkpoint.
+			 */
+			ckpt_active = true;
+			if (!do_restartpoint)
+				ckpt_start_recptr = GetInsertRecPtr();
+			ckpt_start_time = now;
+			ckpt_cached_elapsed = 0;
+
+			/*
+			 * Do the checkpoint.
+			 */
+			if (!do_restartpoint)
+			{
+				CreateCheckPoint(flags);
+				ckpt_performed = true;
+			}
+			else
+				ckpt_performed = CreateRestartPoint(flags);
+
+			/*
+			 * After any checkpoint, close all smgr files.	This is so we
+			 * won't hang onto smgr references to deleted files indefinitely.
+			 */
+			smgrcloseall();
+
+			/*
+			 * Indicate checkpoint completion to any waiting backends.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (ckpt_performed)
+			{
+				/*
+				 * Note we record the checkpoint start time not end time as
+				 * last_checkpoint_time.  This is so that time-driven
+				 * checkpoints happen at a predictable spacing.
+				 */
+				last_checkpoint_time = now;
+			}
+			else
+			{
+				/*
+				 * We were not able to perform the restartpoint (checkpoints
+				 * throw an ERROR in case of error).  Most likely because we
+				 * have not received any new checkpoint WAL records since the
+				 * last restartpoint. Try again in 15 s.
+				 */
+				last_checkpoint_time = now - CheckPointTimeout + 15;
+			}
+
+			ckpt_active = false;
+		}
+
+		/* Check for archive_timeout and switch xlog files if necessary. */
+		CheckArchiveTimeout();
+	}
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ *
+ * This will switch to a new WAL file and force an archive file write
+ * if any activity is recorded in the current WAL file, including just
+ * a single checkpoint record.
+ */
+static void
+CheckArchiveTimeout(void)
+{
+	pg_time_t	now;
+	pg_time_t	last_time;
+
+	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+		return;
+
+	now = (pg_time_t) time(NULL);
+
+	/* First we do a quick check using possibly-stale local state. */
+	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+		return;
+
+	/*
+	 * Update local state ... note that last_xlog_switch_time is the last time
+	 * a switch was performed *or requested*.
+	 */
+	last_time = GetLastSegSwitchTime();
+
+	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+	/* Now we can do the real check */
+	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+	{
+		XLogRecPtr	switchpoint;
+
+		/* OK, it's time to switch */
+		switchpoint = RequestXLogSwitch();
+
+		/*
+		 * If the returned pointer points exactly to a segment boundary,
+		 * assume nothing happened.
+		 */
+		if ((switchpoint.xrecoff % XLogSegSize) != 0)
+			ereport(DEBUG1,
+				(errmsg("transaction log switch forced (archive_timeout=%d)",
+						XLogArchiveTimeout)));
+
+		/*
+		 * Update state in any case, so we don't retry constantly when the
+		 * system is idle.
+		 */
+		last_xlog_switch_time = now;
+	}
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending.	(Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+	if (checkpoint_requested)
+	{
+		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+		/*
+		 * We don't need to acquire the ckpt_lck in this case because we're
+		 * only looking at a single flag bit.
+		 */
+		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * CheckpointWriteDelay -- control rate of checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for throttling BufferSync()'s write rate to hit
+ * checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+	static int	absorb_counter = WRITES_PER_ABSORB;
+
+	/* Do nothing if checkpoint is being executed by non-checkpointer process */
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * Perform the usual duties and take a nap, unless we're behind
+	 * schedule, in which case we just try to catch up as quickly as possible.
+	 */
+	if (!(flags & CHECKPOINT_IMMEDIATE) &&
+		!shutdown_requested &&
+		!ImmediateCheckpointRequested() &&
+		IsCheckpointOnSchedule(progress))
+	{
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+
+		CheckArchiveTimeout();
+
+		/*
+		 * Checkpoint sleep used to be connected to bgwriter_delay at 200ms.
+		 * That resulted in more frequent wakeups if not much work to do.
+		 * Checkpointer and bgwriter are no longer related so take the Big Sleep.
+		 */
+		pg_usleep(500000L);
+	}
+	else if (--absorb_counter <= 0)
+	{
+		/*
+		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+		 * operations even when we don't sleep, to prevent overflow of the
+		 * fsync request queue.
+		 */
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+	}
+}
+
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ *		 in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+	XLogRecPtr	recptr;
+	struct timeval now;
+	double		elapsed_xlogs,
+				elapsed_time;
+
+	Assert(ckpt_active);
+
+	/* Scale progress according to checkpoint_completion_target. */
+	progress *= CheckPointCompletionTarget;
+
+	/*
+	 * Check against the cached value first. Only do the more expensive
+	 * calculations once we reach the target previously calculated. Since
+	 * neither time or WAL insert pointer moves backwards, a freshly
+	 * calculated value can only be greater than or equal to the cached value.
+	 */
+	if (progress < ckpt_cached_elapsed)
+		return false;
+
+	/*
+	 * Check progress against WAL segments written and checkpoint_segments.
+	 *
+	 * We compare the current WAL insert location against the location
+	 * computed before calling CreateCheckPoint. The code in XLogInsert that
+	 * actually triggers a checkpoint when checkpoint_segments is exceeded
+	 * compares against RedoRecptr, so this is not completely accurate.
+	 * However, it's good enough for our purposes, we're only calculating an
+	 * estimate anyway.
+	 */
+	if (!RecoveryInProgress())
+	{
+		recptr = GetInsertRecPtr();
+		elapsed_xlogs =
+			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
+			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
+			CheckPointSegments;
+
+		if (progress < elapsed_xlogs)
+		{
+			ckpt_cached_elapsed = elapsed_xlogs;
+			return false;
+		}
+	}
+
+	/*
+	 * Check progress against time elapsed and checkpoint_timeout.
+	 */
+	gettimeofday(&now, NULL);
+	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+					now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+	if (progress < elapsed_time)
+	{
+		ckpt_cached_elapsed = elapsed_time;
+		return false;
+	}
+
+	/* It looks like we're on schedule. */
+	return true;
+}
+
+
+/* --------------------------------
+ *		signal handler routines
+ * --------------------------------
+ */
+
+/*
+ * chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
+ *
+ * Some backend has bought the farm,
+ * so we need to stop what we're doing and exit.
+ */
+static void
+chkpt_quickdie(SIGNAL_ARGS)
+{
+	PG_SETMASK(&BlockSig);
+
+	/*
+	 * We DO NOT want to run proc_exit() callbacks -- we're here because
+	 * shared memory may be corrupted, so we don't want to try to clean up our
+	 * transaction.  Just nail the windows shut and get out of town.  Now that
+	 * there's an atexit callback to prevent third-party code from breaking
+	 * things by calling exit() directly, we have to reset the callbacks
+	 * explicitly to make this work as intended.
+	 */
+	on_exit_reset();
+
+	/*
+	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
+	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
+	 * backend.  This is necessary precisely because we don't clean up our
+	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
+	 * should ensure the postmaster sees this as a crash, too, but no harm in
+	 * being doubly sure.)
+	 */
+	exit(2);
+}
+
+/* SIGHUP: set flag to re-read config file at next convenient time */
+static void
+ChkptSigHupHandler(SIGNAL_ARGS)
+{
+	got_SIGHUP = true;
+}
+
+/* SIGINT: set flag to run a normal checkpoint right away */
+static void
+ReqCheckpointHandler(SIGNAL_ARGS)
+{
+	checkpoint_requested = true;
+}
+
+/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
+static void
+ReqShutdownHandler(SIGNAL_ARGS)
+{
+	shutdown_requested = true;
+}
+
+
+/* --------------------------------
+ *		communication with backends
+ * --------------------------------
+ */
+
+/*
+ * BgWriterShmemSize
+ *		Compute space needed for bgwriter-related shared memory
+ */
+Size
+BgWriterShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Currently, the size of the requests[] array is arbitrarily set equal to
+	 * NBuffers.  This may prove too large or small ...
+	 */
+	size = offsetof(BgWriterShmemStruct, requests);
+	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
+
+	return size;
+}
+
+/*
+ * BgWriterShmemInit
+ *		Allocate and initialize bgwriter-related shared memory
+ */
+void
+BgWriterShmemInit(void)
+{
+	bool		found;
+
+	BgWriterShmem = (BgWriterShmemStruct *)
+		ShmemInitStruct("Background Writer Data",
+						BgWriterShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
+		SpinLockInit(&BgWriterShmem->ckpt_lck);
+		BgWriterShmem->max_requests = NBuffers;
+	}
+}
+
+/*
+ * RequestCheckpoint
+ *		Called in backend processes to request a checkpoint
+ *
+ * flags is a bitwise OR of the following:
+ *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ *		ignoring checkpoint_completion_target parameter.
+ *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
+ *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ *		CHECKPOINT_END_OF_RECOVERY).
+ *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ *		just signal bgwriter to do it, and return).
+ *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ *		(This affects logging, and in particular enables CheckPointWarning.)
+ */
+void
+RequestCheckpoint(int flags)
+{
+	/* use volatile pointer to prevent code rearrangement */
+	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+	int			ntries;
+	int			old_failed,
+				old_started;
+
+	/*
+	 * If in a standalone backend, just do it ourselves.
+	 */
+	if (!IsPostmasterEnvironment)
+	{
+		/*
+		 * There's no point in doing slow checkpoints in a standalone backend,
+		 * because there's no other backends the checkpoint could disrupt.
+		 */
+		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
+
+		/*
+		 * After any checkpoint, close all smgr files.	This is so we won't
+		 * hang onto smgr references to deleted files indefinitely.
+		 */
+		smgrcloseall();
+
+		return;
+	}
+
+	/*
+	 * Atomically set the request flags, and take a snapshot of the counters.
+	 * When we see ckpt_started > old_started, we know the flags we set here
+	 * have been seen by bgwriter.
+	 *
+	 * Note that we OR the flags with any existing flags, to avoid overriding
+	 * a "stronger" request by another backend.  The flag senses must be
+	 * chosen to make this work!
+	 */
+	SpinLockAcquire(&bgs->ckpt_lck);
+
+	old_failed = bgs->ckpt_failed;
+	old_started = bgs->ckpt_started;
+	bgs->ckpt_flags |= flags;
+
+	SpinLockRelease(&bgs->ckpt_lck);
+
+	/*
+	 * Send signal to request checkpoint.  It's possible that the bgwriter
+	 * hasn't started yet, or is in process of restarting, so we will retry a
+	 * few times if needed.  Also, if not told to wait for the checkpoint to
+	 * occur, we consider failure to send the signal to be nonfatal and merely
+	 * LOG it.
+	 */
+	for (ntries = 0;; ntries++)
+	{
+		if (BgWriterShmem->checkpointer_pid == 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+				"could not request checkpoint because bgwriter not running");
+				break;
+			}
+		}
+		else if (kill(BgWriterShmem->checkpointer_pid, SIGINT) != 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: %m");
+				break;
+			}
+		}
+		else
+			break;				/* signal sent successfully */
+
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
+	}
+
+	/*
+	 * If requested, wait for completion.  We detect completion according to
+	 * the algorithm given above.
+	 */
+	if (flags & CHECKPOINT_WAIT)
+	{
+		int			new_started,
+					new_failed;
+
+		/* Wait for a new checkpoint to start. */
+		for (;;)
+		{
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_started = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_started != old_started)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		/*
+		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
+		 */
+		for (;;)
+		{
+			int			new_done;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_done = bgs->ckpt_done;
+			new_failed = bgs->ckpt_failed;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_done - new_started >= 0)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		if (new_failed != old_failed)
+			ereport(ERROR,
+					(errmsg("checkpoint request failed"),
+					 errhint("Consult recent messages in the server log for details.")));
+	}
+}
+
+/*
+ * ForwardFsyncRequest
+ *		Forward a file-fsync request from a backend to the bgwriter
+ *
+ * Whenever a backend is compelled to write directly to a relation
+ * (which should be seldom, if the bgwriter is getting its job done),
+ * the backend calls this routine to pass over knowledge that the relation
+ * is dirty and must be fsync'd before next checkpoint.  We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * segno specifies which segment (not block!) of the relation needs to be
+ * fsync'd.  (Since the valid range is much less than BlockNumber, we can
+ * use high values for special flags; that's all internal to md.c, which
+ * see for details.)
+ *
+ * To avoid holding the lock for longer than necessary, we normally write
+ * to the requests[] queue without checking for duplicates.  The bgwriter
+ * will have to eliminate dups internally anyway.  However, if we discover
+ * that the queue is full, we make a pass over the entire queue to compact
+ * it.	This is somewhat expensive, but the alternative is for the backend
+ * to perform its own fsync, which is far more expensive in practice.  It
+ * is theoretically possible a backend fsync might still be necessary, if
+ * the queue is full and contains no duplicate entries.  In that case, we
+ * let the backend know by returning false.
+ */
+bool
+ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
+					BlockNumber segno)
+{
+	BgWriterRequest *request;
+
+	if (!IsUnderPostmaster)
+		return false;			/* probably shouldn't even get here */
+
+	if (am_checkpointer)
+		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
+
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Count all backend writes regardless of if they fit in the queue */
+	BgWriterShmem->num_backend_writes++;
+
+	/*
+	 * If the background writer isn't running or the request queue is full,
+	 * the backend will have to perform its own fsync request.	But before
+	 * forcing that to happen, we can try to compact the background writer
+	 * request queue.
+	 */
+	if (BgWriterShmem->checkpointer_pid == 0 ||
+		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
+		 && !CompactCheckpointerRequestQueue()))
+	{
+		/*
+		 * Count the subset of writes where backends have to do their own
+		 * fsync
+		 */
+		BgWriterShmem->num_backend_fsync++;
+		LWLockRelease(BgWriterCommLock);
+		return false;
+	}
+	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
+	request->rnode = rnode;
+	request->forknum = forknum;
+	request->segno = segno;
+	LWLockRelease(BgWriterCommLock);
+	return true;
+}
+
+/*
+ * CompactCheckpointerRequestQueue
+ *		Remove duplicates from the request queue to avoid backend fsyncs.
+ *
+ * Although a full fsync request queue is not common, it can lead to severe
+ * performance problems when it does happen.  So far, this situation has
+ * only been observed to occur when the system is under heavy write load,
+ * and especially during the "sync" phase of a checkpoint.	Without this
+ * logic, each backend begins doing an fsync for every block written, which
+ * gets very expensive and can slow down the whole system.
+ *
+ * Trying to do this every time the queue is full could lose if there
+ * aren't any removable entries.  But should be vanishingly rare in
+ * practice: there's one queue entry per shared buffer.
+ */
+static bool
+CompactCheckpointerRequestQueue()
+{
+	struct BgWriterSlotMapping
+	{
+		BgWriterRequest request;
+		int			slot;
+	};
+
+	int			n,
+				preserve_count;
+	int			num_skipped = 0;
+	HASHCTL		ctl;
+	HTAB	   *htab;
+	bool	   *skip_slot;
+
+	/* must hold BgWriterCommLock in exclusive mode */
+	Assert(LWLockHeldByMe(BgWriterCommLock));
+
+	/* Initialize temporary hash table */
+	MemSet(&ctl, 0, sizeof(ctl));
+	ctl.keysize = sizeof(BgWriterRequest);
+	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
+	ctl.hash = tag_hash;
+	htab = hash_create("CompactBgwriterRequestQueue",
+					   BgWriterShmem->num_requests,
+					   &ctl,
+					   HASH_ELEM | HASH_FUNCTION);
+
+	/* Initialize skip_slot array */
+	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
+
+	/*
+	 * The basic idea here is that a request can be skipped if it's followed
+	 * by a later, identical request.  It might seem more sensible to work
+	 * backwards from the end of the queue and check whether a request is
+	 * *preceded* by an earlier, identical request, in the hopes of doing less
+	 * copying.  But that might change the semantics, if there's an
+	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
+	 * we do it this way.  It would be possible to be even smarter if we made
+	 * the code below understand the specific semantics of such requests (it
+	 * could blow away preceding entries that would end up being canceled
+	 * anyhow), but it's not clear that the extra complexity would buy us
+	 * anything.
+	 */
+	for (n = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		BgWriterRequest *request;
+		struct BgWriterSlotMapping *slotmap;
+		bool		found;
+
+		request = &BgWriterShmem->requests[n];
+		slotmap = hash_search(htab, request, HASH_ENTER, &found);
+		if (found)
+		{
+			skip_slot[slotmap->slot] = true;
+			++num_skipped;
+		}
+		slotmap->slot = n;
+	}
+
+	/* Done with the hash table. */
+	hash_destroy(htab);
+
+	/* If no duplicates, we're out of luck. */
+	if (!num_skipped)
+	{
+		pfree(skip_slot);
+		return false;
+	}
+
+	/* We found some duplicates; remove them. */
+	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		if (skip_slot[n])
+			continue;
+		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
+	}
+	ereport(DEBUG1,
+	   (errmsg("compacted fsync request queue from %d entries to %d entries",
+			   BgWriterShmem->num_requests, preserve_count)));
+	BgWriterShmem->num_requests = preserve_count;
+
+	/* Cleanup. */
+	pfree(skip_slot);
+	return true;
+}
+
+/*
+ * AbsorbFsyncRequests
+ *		Retrieve queued fsync requests and pass them to local smgr.
+ *
+ * This is exported because it must be called during CreateCheckPoint;
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
+ * non-checkpointer processes, do nothing if not checkpointer.
+ */
+void
+AbsorbFsyncRequests(void)
+{
+	BgWriterRequest *requests = NULL;
+	BgWriterRequest *request;
+	int			n;
+
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * We have to PANIC if we fail to absorb all the pending requests (eg,
+	 * because our hashtable runs out of memory).  This is because the system
+	 * cannot run safely if we are unable to fsync what we have been told to
+	 * fsync.  Fortunately, the hashtable is so small that the problem is
+	 * quite unlikely to arise in practice.
+	 */
+	START_CRIT_SECTION();
+
+	/*
+	 * We try to avoid holding the lock for a long time by copying the request
+	 * array.
+	 */
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Transfer write count into pending pgstats message */
+	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
+	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
+
+	BgWriterShmem->num_backend_writes = 0;
+	BgWriterShmem->num_backend_fsync = 0;
+
+	n = BgWriterShmem->num_requests;
+	if (n > 0)
+	{
+		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
+		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
+	}
+	BgWriterShmem->num_requests = 0;
+
+	LWLockRelease(BgWriterCommLock);
+
+	for (request = requests; n > 0; request++, n--)
+		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
+
+	if (requests)
+		pfree(requests);
+
+	END_CRIT_SECTION();
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index df4a2aa..af68741 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -206,6 +206,7 @@ bool		restart_after_crash = true;
 /* PIDs of special child processes; 0 when not running */
 static pid_t StartupPID = 0,
 			BgWriterPID = 0,
+			CheckpointerPID = 0,
 			WalWriterPID = 0,
 			WalReceiverPID = 0,
 			AutoVacPID = 0,
@@ -277,7 +278,7 @@ typedef enum
 	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
 	PM_WAIT_READONLY,			/* waiting for read only backends to exit */
 	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
-	PM_SHUTDOWN,				/* waiting for bgwriter to do shutdown ckpt */
+	PM_SHUTDOWN,				/* waiting for checkpointer to do shutdown ckpt */
 	PM_SHUTDOWN_2,				/* waiting for archiver and walsenders to
 								 * finish */
 	PM_WAIT_DEAD_END,			/* waiting for dead_end children to exit */
@@ -462,6 +463,7 @@ static void ShmemBackendArrayRemove(Backend *bn);
 
 #define StartupDataBase()		StartChildProcess(StartupProcess)
 #define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
+#define StartCheckpointer()		StartChildProcess(CheckpointerProcess)
 #define StartWalWriter()		StartChildProcess(WalWriterProcess)
 #define StartWalReceiver()		StartChildProcess(WalReceiverProcess)
 
@@ -1029,8 +1031,8 @@ PostmasterMain(int argc, char *argv[])
 	 * CAUTION: when changing this list, check for side-effects on the signal
 	 * handling setup of child processes.  See tcop/postgres.c,
 	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
-	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c, and
-	 * postmaster/syslogger.c.
+	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
+	 * postmaster/syslogger.c and postmaster/checkpointer.c
 	 */
 	pqinitmask();
 	PG_SETMASK(&BlockSig);
@@ -1367,10 +1369,14 @@ ServerLoop(void)
 		 * state that prevents it, start one.  It doesn't matter if this
 		 * fails, we'll just try again later.
 		 */
-		if (BgWriterPID == 0 &&
-			(pmState == PM_RUN || pmState == PM_RECOVERY ||
-			 pmState == PM_HOT_STANDBY))
-			BgWriterPID = StartBackgroundWriter();
+		if (pmState == PM_RUN || pmState == PM_RECOVERY ||
+			 pmState == PM_HOT_STANDBY)
+		{
+			if (BgWriterPID == 0)
+				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
+		}
 
 		/*
 		 * Likewise, if we have lost the walwriter process, try to start a new
@@ -2048,6 +2054,8 @@ SIGHUP_handler(SIGNAL_ARGS)
 			signal_child(StartupPID, SIGHUP);
 		if (BgWriterPID != 0)
 			signal_child(BgWriterPID, SIGHUP);
+		if (CheckpointerPID != 0)
+			signal_child(CheckpointerPID, SIGHUP);
 		if (WalWriterPID != 0)
 			signal_child(WalWriterPID, SIGHUP);
 		if (WalReceiverPID != 0)
@@ -2162,7 +2170,7 @@ pmdie(SIGNAL_ARGS)
 				signal_child(WalReceiverPID, SIGTERM);
 			if (pmState == PM_RECOVERY)
 			{
-				/* only bgwriter is active in this state */
+				/* only checkpointer is active in this state */
 				pmState = PM_WAIT_BACKENDS;
 			}
 			else if (pmState == PM_RUN ||
@@ -2207,6 +2215,8 @@ pmdie(SIGNAL_ARGS)
 				signal_child(StartupPID, SIGQUIT);
 			if (BgWriterPID != 0)
 				signal_child(BgWriterPID, SIGQUIT);
+			if (CheckpointerPID != 0)
+				signal_child(CheckpointerPID, SIGQUIT);
 			if (WalWriterPID != 0)
 				signal_child(WalWriterPID, SIGQUIT);
 			if (WalReceiverPID != 0)
@@ -2337,12 +2347,14 @@ reaper(SIGNAL_ARGS)
 			}
 
 			/*
-			 * Crank up the background writer, if we didn't do that already
+			 * Crank up background tasks, if we didn't do that already
 			 * when we entered consistent recovery state.  It doesn't matter
 			 * if this fails, we'll just try again later.
 			 */
 			if (BgWriterPID == 0)
 				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
 
 			/*
 			 * Likewise, start other special children as needed.  In a restart
@@ -2370,10 +2382,22 @@ reaper(SIGNAL_ARGS)
 		if (pid == BgWriterPID)
 		{
 			BgWriterPID = 0;
+			if (!EXIT_STATUS_0(exitstatus))
+				HandleChildCrash(pid, exitstatus,
+								 _("background writer process"));
+			continue;
+		}
+
+		/*
+		 * Was it the checkpointer?
+		 */
+		if (pid == CheckpointerPID)
+		{
+			CheckpointerPID = 0;
 			if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
 			{
 				/*
-				 * OK, we saw normal exit of the bgwriter after it's been told
+				 * OK, we saw normal exit of the checkpointer after it's been told
 				 * to shut down.  We expect that it wrote a shutdown
 				 * checkpoint.	(If for some reason it didn't, recovery will
 				 * occur on next postmaster start.)
@@ -2410,11 +2434,11 @@ reaper(SIGNAL_ARGS)
 			else
 			{
 				/*
-				 * Any unexpected exit of the bgwriter (including FATAL exit)
+				 * Any unexpected exit of the checkpointer (including FATAL exit)
 				 * is treated as a crash.
 				 */
 				HandleChildCrash(pid, exitstatus,
-								 _("background writer process"));
+								 _("checkpointer process"));
 			}
 
 			continue;
@@ -2598,8 +2622,8 @@ CleanupBackend(int pid,
 }
 
 /*
- * HandleChildCrash -- cleanup after failed backend, bgwriter, walwriter,
- * or autovacuum.
+ * HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
+ * walwriter or autovacuum.
  *
  * The objectives here are to clean up our local state about the child
  * process, and to signal all other remaining children to quickdie.
@@ -2692,6 +2716,18 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 		signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
 	}
 
+	/* Take care of the checkpointer too */
+	if (pid == CheckpointerPID)
+		CheckpointerPID = 0;
+	else if (CheckpointerPID != 0 && !FatalError)
+	{
+		ereport(DEBUG2,
+				(errmsg_internal("sending %s to process %d",
+								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
+								 (int) CheckpointerPID)));
+		signal_child(CheckpointerPID, (SendStop ? SIGSTOP : SIGQUIT));
+	}
+
 	/* Take care of the walwriter too */
 	if (pid == WalWriterPID)
 		WalWriterPID = 0;
@@ -2871,9 +2907,10 @@ PostmasterStateMachine(void)
 	{
 		/*
 		 * PM_WAIT_BACKENDS state ends when we have no regular backends
-		 * (including autovac workers) and no walwriter or autovac launcher.
-		 * If we are doing crash recovery then we expect the bgwriter to exit
-		 * too, otherwise not.	The archiver, stats, and syslogger processes
+		 * (including autovac workers) and no walwriter, autovac launcher
+		 * or bgwriter.  If we are doing crash recovery then we expect the
+		 * checkpointer to exit as well, otherwise not.
+		 * The archiver, stats, and syslogger processes
 		 * are disregarded since they are not connected to shared memory; we
 		 * also disregard dead_end children here. Walsenders are also
 		 * disregarded, they will be terminated later after writing the
@@ -2882,7 +2919,8 @@ PostmasterStateMachine(void)
 		if (CountChildren(BACKEND_TYPE_NORMAL | BACKEND_TYPE_AUTOVAC) == 0 &&
 			StartupPID == 0 &&
 			WalReceiverPID == 0 &&
-			(BgWriterPID == 0 || !FatalError) &&
+			BgWriterPID == 0 &&
+			(CheckpointerPID == 0 || !FatalError) &&
 			WalWriterPID == 0 &&
 			AutoVacPID == 0)
 		{
@@ -2904,22 +2942,22 @@ PostmasterStateMachine(void)
 				/*
 				 * If we get here, we are proceeding with normal shutdown. All
 				 * the regular children are gone, and it's time to tell the
-				 * bgwriter to do a shutdown checkpoint.
+				 * checkpointer to do a shutdown checkpoint.
 				 */
 				Assert(Shutdown > NoShutdown);
-				/* Start the bgwriter if not running */
-				if (BgWriterPID == 0)
-					BgWriterPID = StartBackgroundWriter();
+				/* Start the checkpointer if not running */
+				if (CheckpointerPID == 0)
+					CheckpointerPID = StartCheckpointer();
 				/* And tell it to shut down */
-				if (BgWriterPID != 0)
+				if (CheckpointerPID != 0)
 				{
-					signal_child(BgWriterPID, SIGUSR2);
+					signal_child(CheckpointerPID, SIGUSR2);
 					pmState = PM_SHUTDOWN;
 				}
 				else
 				{
 					/*
-					 * If we failed to fork a bgwriter, just shut down. Any
+					 * If we failed to fork a checkpointer, just shut down. Any
 					 * required cleanup will happen at next restart. We set
 					 * FatalError so that an "abnormal shutdown" message gets
 					 * logged when we exit.
@@ -2978,6 +3016,7 @@ PostmasterStateMachine(void)
 			Assert(StartupPID == 0);
 			Assert(WalReceiverPID == 0);
 			Assert(BgWriterPID == 0);
+			Assert(CheckpointerPID == 0);
 			Assert(WalWriterPID == 0);
 			Assert(AutoVacPID == 0);
 			/* syslogger is not considered here */
@@ -4157,6 +4196,8 @@ sigusr1_handler(SIGNAL_ARGS)
 		 */
 		Assert(BgWriterPID == 0);
 		BgWriterPID = StartBackgroundWriter();
+		Assert(CheckpointerPID == 0);
+		CheckpointerPID = StartCheckpointer();
 
 		pmState = PM_RECOVERY;
 	}
@@ -4443,6 +4484,10 @@ StartChildProcess(AuxProcType type)
 				ereport(LOG,
 				   (errmsg("could not fork background writer process: %m")));
 				break;
+			case CheckpointerProcess:
+				ereport(LOG,
+				   (errmsg("could not fork checkpointer process: %m")));
+				break;
 			case WalWriterProcess:
 				ereport(LOG,
 						(errmsg("could not fork WAL writer process: %m")));
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8647edd..184e820 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1278,11 +1278,9 @@ BufferSync(int flags)
 					break;
 
 				/*
-				 * Perform normal bgwriter duties and sleep to throttle our
-				 * I/O rate.
+				 * Sleep to throttle our I/O rate.
 				 */
-				CheckpointWriteDelay(flags,
-									 (double) num_written / num_to_write);
+				CheckpointWriteDelay(flags, (double) num_written / num_to_write);
 			}
 		}
 
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 3015885..a761369 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -38,7 +38,7 @@
 /*
  * Special values for the segno arg to RememberFsyncRequest.
  *
- * Note that CompactBgwriterRequestQueue assumes that it's OK to remove an
+ * Note that CompactcheckpointerRequestQueue assumes that it's OK to remove an
  * fsync request from the queue if an identical, subsequent request is found.
  * See comments there before making changes here.
  */
@@ -77,7 +77,7 @@
  *	Inactive segments are those that once contained data but are currently
  *	not needed because of an mdtruncate() operation.  The reason for leaving
  *	them present at size zero, rather than unlinking them, is that other
- *	backends and/or the bgwriter might be holding open file references to
+ *	backends and/or the checkpointer might be holding open file references to
  *	such segments.	If the relation expands again after mdtruncate(), such
  *	that a deactivated segment becomes active again, it is important that
  *	such file references still be valid --- else data might get written
@@ -111,7 +111,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
 
 
 /*
- * In some contexts (currently, standalone backends and the bgwriter process)
+ * In some contexts (currently, standalone backends and the checkpointer process)
  * we keep track of pending fsync operations: we need to remember all relation
  * segments that have been written since the last checkpoint, so that we can
  * fsync them down to disk before completing the next checkpoint.  This hash
@@ -123,7 +123,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
  * a hash table, because we don't expect there to be any duplicate requests.
  *
  * (Regular backends do not track pending operations locally, but forward
- * them to the bgwriter.)
+ * them to the checkpointer.)
  */
 typedef struct
 {
@@ -194,7 +194,7 @@ mdinit(void)
 	 * Create pending-operations hashtable if we need it.  Currently, we need
 	 * it if we are standalone (not under a postmaster) OR if we are a
 	 * bootstrap-mode subprocess of a postmaster (that is, a startup or
-	 * bgwriter process).
+	 * checkpointer process).
 	 */
 	if (!IsUnderPostmaster || IsBootstrapProcessingMode())
 	{
@@ -214,10 +214,10 @@ mdinit(void)
 }
 
 /*
- * In archive recovery, we rely on bgwriter to do fsyncs, but we will have
+ * In archive recovery, we rely on checkpointer to do fsyncs, but we will have
  * already created the pendingOpsTable during initialization of the startup
  * process.  Calling this function drops the local pendingOpsTable so that
- * subsequent requests will be forwarded to bgwriter.
+ * subsequent requests will be forwarded to checkpointer.
  */
 void
 SetForwardFsyncRequests(void)
@@ -765,9 +765,9 @@ mdnblocks(SMgrRelation reln, ForkNumber forknum)
 	 * NOTE: this assumption could only be wrong if another backend has
 	 * truncated the relation.	We rely on higher code levels to handle that
 	 * scenario by closing and re-opening the md fd, which is handled via
-	 * relcache flush.	(Since the bgwriter doesn't participate in relcache
+	 * relcache flush.	(Since the checkpointer doesn't participate in relcache
 	 * flush, it could have segment chain entries for inactive segments;
-	 * that's OK because the bgwriter never needs to compute relation size.)
+	 * that's OK because the checkpointer never needs to compute relation size.)
 	 */
 	while (v->mdfd_chain != NULL)
 	{
@@ -957,7 +957,7 @@ mdsync(void)
 		elog(ERROR, "cannot sync without a pendingOpsTable");
 
 	/*
-	 * If we are in the bgwriter, the sync had better include all fsync
+	 * If we are in the checkpointer, the sync had better include all fsync
 	 * requests that were queued by backends up to this point.	The tightest
 	 * race condition that could occur is that a buffer that must be written
 	 * and fsync'd for the checkpoint could have been dumped by a backend just
@@ -1033,7 +1033,7 @@ mdsync(void)
 			int			failures;
 
 			/*
-			 * If in bgwriter, we want to absorb pending requests every so
+			 * If in checkpointer, we want to absorb pending requests every so
 			 * often to prevent overflow of the fsync request queue.  It is
 			 * unspecified whether newly-added entries will be visited by
 			 * hash_seq_search, but we don't care since we don't need to
@@ -1070,9 +1070,9 @@ mdsync(void)
 				 * say "but an unreferenced SMgrRelation is still a leak!" Not
 				 * really, because the only case in which a checkpoint is done
 				 * by a process that isn't about to shut down is in the
-				 * bgwriter, and it will periodically do smgrcloseall(). This
+				 * checkpointer, and it will periodically do smgrcloseall(). This
 				 * fact justifies our not closing the reln in the success path
-				 * either, which is a good thing since in non-bgwriter cases
+				 * either, which is a good thing since in non-checkpointer cases
 				 * we couldn't safely do that.)  Furthermore, in many cases
 				 * the relation will have been dirtied through this same smgr
 				 * relation, and so we can save a file open/close cycle.
@@ -1301,7 +1301,7 @@ register_unlink(RelFileNodeBackend rnode)
 	else
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the request
+		 * Notify the checkpointer about it.  If we fail to queue the request
 		 * message, we have to sleep and try again, because we can't simply
 		 * delete the file now.  Ugly, but hopefully won't happen often.
 		 *
@@ -1315,10 +1315,10 @@ register_unlink(RelFileNodeBackend rnode)
 }
 
 /*
- * RememberFsyncRequest() -- callback from bgwriter side of fsync request
+ * RememberFsyncRequest() -- callback from checkpointer side of fsync request
  *
  * We stuff most fsync requests into the local hash table for execution
- * during the bgwriter's next checkpoint.  UNLINK requests go into a
+ * during the checkpointer's next checkpoint.  UNLINK requests go into a
  * separate linked list, however, because they get processed separately.
  *
  * The range of possible segment numbers is way less than the range of
@@ -1460,20 +1460,20 @@ ForgetRelationFsyncRequests(RelFileNodeBackend rnode, ForkNumber forknum)
 	else if (IsUnderPostmaster)
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the revoke
+		 * Notify the checkpointer about it.  If we fail to queue the revoke
 		 * message, we have to sleep and try again ... ugly, but hopefully
 		 * won't happen often.
 		 *
 		 * XXX should we CHECK_FOR_INTERRUPTS in this loop?  Escaping with an
 		 * error would leave the no-longer-used file still present on disk,
-		 * which would be bad, so I'm inclined to assume that the bgwriter
+		 * which would be bad, so I'm inclined to assume that the checkpointer
 		 * will always empty the queue soon.
 		 */
 		while (!ForwardFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC))
 			pg_usleep(10000L);	/* 10 msec seems a good number */
 
 		/*
-		 * Note we don't wait for the bgwriter to actually absorb the revoke
+		 * Note we don't wait for the checkpointer to actually absorb the revoke
 		 * message; see mdsync() for the implications.
 		 */
 	}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 4eaa243..cb43879 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -256,7 +256,7 @@ typedef struct RmgrData
 extern const RmgrData RmgrTable[];
 
 /*
- * Exported to support xlog switching from bgwriter
+ * Exported to support xlog switching from checkpointer
  */
 extern pg_time_t GetLastSegSwitchTime(void);
 extern XLogRecPtr RequestXLogSwitch(void);
diff --git a/src/include/bootstrap/bootstrap.h b/src/include/bootstrap/bootstrap.h
index cee9bd1..6153b7a 100644
--- a/src/include/bootstrap/bootstrap.h
+++ b/src/include/bootstrap/bootstrap.h
@@ -22,6 +22,7 @@ typedef enum
 	BootstrapProcess,
 	StartupProcess,
 	BgWriterProcess,
+	CheckpointerProcess,
 	WalWriterProcess,
 	WalReceiverProcess,
 
diff --git a/src/include/postmaster/bgwriter.h b/src/include/postmaster/bgwriter.h
index eaf2206..c05901e 100644
--- a/src/include/postmaster/bgwriter.h
+++ b/src/include/postmaster/bgwriter.h
@@ -23,6 +23,7 @@ extern int	CheckPointWarning;
 extern double CheckPointCompletionTarget;
 
 extern void BackgroundWriterMain(void);
+extern void CheckpointerMain(void);
 
 extern void RequestCheckpoint(int flags);
 extern void CheckpointWriteDelay(int flags, double progress);
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 46ec625..6e798b1 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -190,11 +190,11 @@ extern PROC_HDR *ProcGlobal;
  * We set aside some extra PGPROC structures for auxiliary processes,
  * ie things that aren't full-fledged backends but need shmem access.
  *
- * Background writer and WAL writer run during normal operation. Startup
- * process and WAL receiver also consume 2 slots, but WAL writer is
- * launched only after startup has exited, so we only need 3 slots.
+ * Background writer, checkpointer and WAL writer run during normal operation.
+ * Startup process and WAL receiver also consume 2 slots, but WAL writer is
+ * launched only after startup has exited, so we only need 4 slots.
  */
-#define NUM_AUXILIARY_PROCS		3
+#define NUM_AUXILIARY_PROCS		4
 
 
 /* configurable options */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 2a27e0b..d5afe01 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -19,7 +19,7 @@
 
 /*
  * Reasons for signalling a Postgres child process (a backend or an auxiliary
- * process, like bgwriter).  We can cope with concurrent signals for different
+ * process, like checkpointer).  We can cope with concurrent signals for different
  * reasons.  However, if the same reason is signaled multiple times in quick
  * succession, the process is likely to observe only one notification of it.
  * This is okay for the present uses.

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 4fe08df..f9b839c 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -315,6 +315,9 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			case BgWriterProcess:
 				statmsg = "writer process";
 				break;
+			case CheckpointerProcess:
+				statmsg = "checkpointer process";
+				break;
 			case WalWriterProcess:
 				statmsg = "wal writer process";
 				break;
@@ -415,6 +418,11 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			BackgroundWriterMain();
 			proc_exit(1);		/* should never return */
 
+		case CheckpointerProcess:
+			/* don't set signals, checkpointer has its own agenda */
+			CheckpointerMain();
+			proc_exit(1);		/* should never return */
+
 		case WalWriterProcess:
 			/* don't set signals, walwriter has its own agenda */
 			InitXLOGAccess();
diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 0767e97..e7414d2 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -13,6 +13,6 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = autovacuum.o bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o \
-	syslogger.o walwriter.o
+	syslogger.o walwriter.o checkpointer.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2d0b639..e0f3167 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -10,20 +10,13 @@
  * still empowered to issue writes if the bgwriter fails to maintain enough
  * clean shared buffers.
  *
- * The bgwriter is also charged with handling all checkpoints.	It will
- * automatically dispatch a checkpoint after a certain amount of time has
- * elapsed since the last one, and it can be signaled to perform requested
- * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
- * so many WAL segments is implemented by having backends signal the bgwriter
- * when they fill WAL segments; the bgwriter itself doesn't watch for the
- * condition.)
+ * As of Postgres 9.2 the bgwriter no longer handles checkpoints.
  *
  * The bgwriter is started by the postmaster as soon as the startup subprocess
  * finishes, or as soon as recovery begins if we are doing archive recovery.
  * It remains alive until the postmaster commands it to terminate.
- * Normal termination is by SIGUSR2, which instructs the bgwriter to execute
- * a shutdown checkpoint and then exit(0).	(All backends must be stopped
- * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
+ * Emergency termination is by SIGQUIT; like any
  * backend, the bgwriter will simply abort and exit on SIGQUIT.
  *
  * If the bgwriter exits unexpectedly, the postmaster treats that the same
@@ -54,7 +47,6 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
-#include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
@@ -67,96 +59,15 @@
 #include "utils/resowner.h"
 
 
-/*----------
- * Shared memory area for communication between bgwriter and backends
- *
- * The ckpt counters allow backends to watch for completion of a checkpoint
- * request they send.  Here's how it works:
- *	* At start of a checkpoint, bgwriter reads (and clears) the request flags
- *	  and increments ckpt_started, while holding ckpt_lck.
- *	* On completion of a checkpoint, bgwriter sets ckpt_done to
- *	  equal ckpt_started.
- *	* On failure of a checkpoint, bgwriter increments ckpt_failed
- *	  and sets ckpt_done to equal ckpt_started.
- *
- * The algorithm for backends is:
- *	1. Record current values of ckpt_failed and ckpt_started, and
- *	   set request flags, while holding ckpt_lck.
- *	2. Send signal to request checkpoint.
- *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
- *	   begun since you started this algorithm (although *not* that it was
- *	   specifically initiated by your signal), and that it is using your flags.
- *	4. Record new value of ckpt_started.
- *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
- *	   arithmetic here in case counters wrap around.)  Now you know a
- *	   checkpoint has started and completed, but not whether it was
- *	   successful.
- *	6. If ckpt_failed is different from the originally saved value,
- *	   assume request failed; otherwise it was definitely successful.
- *
- * ckpt_flags holds the OR of the checkpoint request flags sent by all
- * requesting backends since the last checkpoint start.  The flags are
- * chosen so that OR'ing is the correct way to combine multiple requests.
- *
- * num_backend_writes is used to count the number of buffer writes performed
- * by non-bgwriter processes.  This counter should be wide enough that it
- * can't overflow during a single bgwriter cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the background writer failed to absorb their request.
- *
- * The requests array holds fsync requests sent by backends and not yet
- * absorbed by the bgwriter.
- *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by BgWriterCommLock.
- *----------
- */
-typedef struct
-{
-	RelFileNodeBackend rnode;
-	ForkNumber	forknum;
-	BlockNumber segno;			/* see md.c for special values */
-	/* might add a real request-type field later; not needed yet */
-} BgWriterRequest;
-
-typedef struct
-{
-	pid_t		bgwriter_pid;	/* PID of bgwriter (0 if not started) */
-
-	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
-
-	int			ckpt_started;	/* advances when checkpoint starts */
-	int			ckpt_done;		/* advances when checkpoint done */
-	int			ckpt_failed;	/* advances when checkpoint fails */
-
-	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
-
-	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
-	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
-
-	int			num_requests;	/* current # of requests */
-	int			max_requests;	/* allocated array size */
-	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
-} BgWriterShmemStruct;
-
-static BgWriterShmemStruct *BgWriterShmem;
-
-/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
-#define WRITES_PER_ABSORB		1000
-
 /*
  * GUC parameters
  */
 int			BgWriterDelay = 200;
-int			CheckPointTimeout = 300;
-int			CheckPointWarning = 30;
-double		CheckPointCompletionTarget = 0.5;
 
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
 static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t checkpoint_requested = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -164,29 +75,14 @@ static volatile sig_atomic_t shutdown_requested = false;
  */
 static bool am_bg_writer = false;
 
-static bool ckpt_active = false;
-
-/* these values are valid when ckpt_active is true: */
-static pg_time_t ckpt_start_time;
-static XLogRecPtr ckpt_start_recptr;
-static double ckpt_cached_elapsed;
-
-static pg_time_t last_checkpoint_time;
-static pg_time_t last_xlog_switch_time;
-
 /* Prototypes for private functions */
 
-static void CheckArchiveTimeout(void);
 static void BgWriterNap(void);
-static bool IsCheckpointOnSchedule(double progress);
-static bool ImmediateCheckpointRequested(void);
-static bool CompactBgwriterRequestQueue(void);
 
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
 static void BgSigHupHandler(SIGNAL_ARGS);
-static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -202,7 +98,6 @@ BackgroundWriterMain(void)
 	sigjmp_buf	local_sigjmp_buf;
 	MemoryContext bgwriter_context;
 
-	BgWriterShmem->bgwriter_pid = MyProcPid;
 	am_bg_writer = true;
 
 	/*
@@ -228,8 +123,8 @@ BackgroundWriterMain(void)
 	 * process to participate in ProcSignal signalling.
 	 */
 	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
-	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
-	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
+	pqsignal(SIGINT, SIG_IGN);			/* as of 9.2 no longer requests checkpoint */
+	pqsignal(SIGTERM, SIG_IGN); 		/* ignore SIGTERM */
 	pqsignal(SIGQUIT, bg_quickdie);		/* hard crash time */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -249,11 +144,6 @@ BackgroundWriterMain(void)
 	sigdelset(&BlockSig, SIGQUIT);
 
 	/*
-	 * Initialize so that first time-driven event happens at the correct time.
-	 */
-	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
-
-	/*
 	 * Create a resource owner to keep track of our resources (currently only
 	 * buffer pins).
 	 */
@@ -305,20 +195,6 @@ BackgroundWriterMain(void)
 		AtEOXact_Files();
 		AtEOXact_HashTables(false);
 
-		/* Warn any waiting backends that the checkpoint failed. */
-		if (ckpt_active)
-		{
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_failed++;
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			ckpt_active = false;
-		}
-
 		/*
 		 * Now return to normal top-level context and clear ErrorContext for
 		 * next time.
@@ -361,19 +237,11 @@ BackgroundWriterMain(void)
 	if (RecoveryInProgress())
 		ThisTimeLineID = GetRecoveryTargetTLI();
 
-	/* Do this once before starting the loop, then just at SIGHUP time. */
-	SyncRepUpdateSyncStandbysDefined();
-
 	/*
 	 * Loop forever
 	 */
 	for (;;)
 	{
-		bool		do_checkpoint = false;
-		int			flags = 0;
-		pg_time_t	now;
-		int			elapsed_secs;
-
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -381,23 +249,11 @@ BackgroundWriterMain(void)
 		if (!PostmasterIsAlive())
 			exit(1);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		AbsorbFsyncRequests();
-
 		if (got_SIGHUP)
 		{
 			got_SIGHUP = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-		if (checkpoint_requested)
-		{
-			checkpoint_requested = false;
-			do_checkpoint = true;
-			BgWriterStats.m_requested_checkpoints++;
 		}
 		if (shutdown_requested)
 		{
@@ -406,142 +262,14 @@ BackgroundWriterMain(void)
 			 * control back to the sigsetjmp block above
 			 */
 			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
 			/* Normal exit from the bgwriter is here */
 			proc_exit(0);		/* done */
 		}
 
 		/*
-		 * Force a checkpoint if too much time has elapsed since the last one.
-		 * Note that we count a timed checkpoint in stats only when this
-		 * occurs without an external request, but we set the CAUSE_TIME flag
-		 * bit even if there is also an external request.
+		 * Do one cycle of dirty-buffer writing.
 		 */
-		now = (pg_time_t) time(NULL);
-		elapsed_secs = now - last_checkpoint_time;
-		if (elapsed_secs >= CheckPointTimeout)
-		{
-			if (!do_checkpoint)
-				BgWriterStats.m_timed_checkpoints++;
-			do_checkpoint = true;
-			flags |= CHECKPOINT_CAUSE_TIME;
-		}
-
-		/*
-		 * Do a checkpoint if requested, otherwise do one cycle of
-		 * dirty-buffer writing.
-		 */
-		if (do_checkpoint)
-		{
-			bool		ckpt_performed = false;
-			bool		do_restartpoint;
-
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			/*
-			 * Check if we should perform a checkpoint or a restartpoint. As a
-			 * side-effect, RecoveryInProgress() initializes TimeLineID if
-			 * it's not set yet.
-			 */
-			do_restartpoint = RecoveryInProgress();
-
-			/*
-			 * Atomically fetch the request flags to figure out what kind of a
-			 * checkpoint we should perform, and increase the started-counter
-			 * to acknowledge that we've started a new checkpoint.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			flags |= bgs->ckpt_flags;
-			bgs->ckpt_flags = 0;
-			bgs->ckpt_started++;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			/*
-			 * The end-of-recovery checkpoint is a real checkpoint that's
-			 * performed while we're still in recovery.
-			 */
-			if (flags & CHECKPOINT_END_OF_RECOVERY)
-				do_restartpoint = false;
-
-			/*
-			 * We will warn if (a) too soon since last checkpoint (whatever
-			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
-			 * since the last checkpoint start.  Note in particular that this
-			 * implementation will not generate warnings caused by
-			 * CheckPointTimeout < CheckPointWarning.
-			 */
-			if (!do_restartpoint &&
-				(flags & CHECKPOINT_CAUSE_XLOG) &&
-				elapsed_secs < CheckPointWarning)
-				ereport(LOG,
-						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
-				"checkpoints are occurring too frequently (%d seconds apart)",
-									   elapsed_secs,
-									   elapsed_secs),
-						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
-
-			/*
-			 * Initialize bgwriter-private variables used during checkpoint.
-			 */
-			ckpt_active = true;
-			if (!do_restartpoint)
-				ckpt_start_recptr = GetInsertRecPtr();
-			ckpt_start_time = now;
-			ckpt_cached_elapsed = 0;
-
-			/*
-			 * Do the checkpoint.
-			 */
-			if (!do_restartpoint)
-			{
-				CreateCheckPoint(flags);
-				ckpt_performed = true;
-			}
-			else
-				ckpt_performed = CreateRestartPoint(flags);
-
-			/*
-			 * After any checkpoint, close all smgr files.	This is so we
-			 * won't hang onto smgr references to deleted files indefinitely.
-			 */
-			smgrcloseall();
-
-			/*
-			 * Indicate checkpoint completion to any waiting backends.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (ckpt_performed)
-			{
-				/*
-				 * Note we record the checkpoint start time not end time as
-				 * last_checkpoint_time.  This is so that time-driven
-				 * checkpoints happen at a predictable spacing.
-				 */
-				last_checkpoint_time = now;
-			}
-			else
-			{
-				/*
-				 * We were not able to perform the restartpoint (checkpoints
-				 * throw an ERROR in case of error).  Most likely because we
-				 * have not received any new checkpoint WAL records since the
-				 * last restartpoint. Try again in 15 s.
-				 */
-				last_checkpoint_time = now - CheckPointTimeout + 15;
-			}
-
-			ckpt_active = false;
-		}
-		else
-			BgBufferSync();
-
-		/* Check for archive_timeout and switch xlog files if necessary. */
-		CheckArchiveTimeout();
+		BgBufferSync();
 
 		/* Nap for the configured time. */
 		BgWriterNap();
@@ -549,61 +277,6 @@ BackgroundWriterMain(void)
 }
 
 /*
- * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
- *
- * This will switch to a new WAL file and force an archive file write
- * if any activity is recorded in the current WAL file, including just
- * a single checkpoint record.
- */
-static void
-CheckArchiveTimeout(void)
-{
-	pg_time_t	now;
-	pg_time_t	last_time;
-
-	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
-		return;
-
-	now = (pg_time_t) time(NULL);
-
-	/* First we do a quick check using possibly-stale local state. */
-	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
-		return;
-
-	/*
-	 * Update local state ... note that last_xlog_switch_time is the last time
-	 * a switch was performed *or requested*.
-	 */
-	last_time = GetLastSegSwitchTime();
-
-	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
-
-	/* Now we can do the real check */
-	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
-	{
-		XLogRecPtr	switchpoint;
-
-		/* OK, it's time to switch */
-		switchpoint = RequestXLogSwitch();
-
-		/*
-		 * If the returned pointer points exactly to a segment boundary,
-		 * assume nothing happened.
-		 */
-		if ((switchpoint.xrecoff % XLogSegSize) != 0)
-			ereport(DEBUG1,
-				(errmsg("transaction log switch forced (archive_timeout=%d)",
-						XLogArchiveTimeout)));
-
-		/*
-		 * Update state in any case, so we don't retry constantly when the
-		 * system is idle.
-		 */
-		last_xlog_switch_time = now;
-	}
-}
-
-/*
  * BgWriterNap -- Nap for the configured time or until a signal is received.
  */
 static void
@@ -624,185 +297,24 @@ BgWriterNap(void)
 	 * respond reasonably promptly when someone signals us, break down the
 	 * sleep into 1-second increments, and check for interrupts after each
 	 * nap.
-	 *
-	 * We absorb pending requests after each short sleep.
 	 */
-	if (bgwriter_lru_maxpages > 0 || ckpt_active)
+	if (bgwriter_lru_maxpages > 0)
 		udelay = BgWriterDelay * 1000L;
-	else if (XLogArchiveTimeout > 0)
-		udelay = 1000000L;		/* One second */
 	else
 		udelay = 10000000L;		/* Ten seconds */
 
 	while (udelay > 999999L)
 	{
-		if (got_SIGHUP || shutdown_requested ||
-		(ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested))
+		if (got_SIGHUP || shutdown_requested)
 			break;
 		pg_usleep(1000000L);
-		AbsorbFsyncRequests();
 		udelay -= 1000000L;
 	}
 
-	if (!(got_SIGHUP || shutdown_requested ||
-	  (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested)))
+	if (!(got_SIGHUP || shutdown_requested))
 		pg_usleep(udelay);
 }
 
-/*
- * Returns true if an immediate checkpoint request is pending.	(Note that
- * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
- * there is one pending behind it.)
- */
-static bool
-ImmediateCheckpointRequested(void)
-{
-	if (checkpoint_requested)
-	{
-		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-		/*
-		 * We don't need to acquire the ckpt_lck in this case because we're
-		 * only looking at a single flag bit.
-		 */
-		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
-			return true;
-	}
-	return false;
-}
-
-/*
- * CheckpointWriteDelay -- yield control to bgwriter during a checkpoint
- *
- * This function is called after each page write performed by BufferSync().
- * It is responsible for keeping the bgwriter's normal activities in
- * progress during a long checkpoint, and for throttling BufferSync()'s
- * write rate to hit checkpoint_completion_target.
- *
- * The checkpoint request flags should be passed in; currently the only one
- * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
- *
- * 'progress' is an estimate of how much of the work has been done, as a
- * fraction between 0.0 meaning none, and 1.0 meaning all done.
- */
-void
-CheckpointWriteDelay(int flags, double progress)
-{
-	static int	absorb_counter = WRITES_PER_ABSORB;
-
-	/* Do nothing if checkpoint is being executed by non-bgwriter process */
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * Perform the usual bgwriter duties and take a nap, unless we're behind
-	 * schedule, in which case we just try to catch up as quickly as possible.
-	 */
-	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
-		!ImmediateCheckpointRequested() &&
-		IsCheckpointOnSchedule(progress))
-	{
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-
-		BgBufferSync();
-		CheckArchiveTimeout();
-		BgWriterNap();
-	}
-	else if (--absorb_counter <= 0)
-	{
-		/*
-		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
-		 * operations even when we don't sleep, to prevent overflow of the
-		 * fsync request queue.
-		 */
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-	}
-}
-
-/*
- * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
- *		 in time?
- *
- * Compares the current progress against the time/segments elapsed since last
- * checkpoint, and returns true if the progress we've made this far is greater
- * than the elapsed time/segments.
- */
-static bool
-IsCheckpointOnSchedule(double progress)
-{
-	XLogRecPtr	recptr;
-	struct timeval now;
-	double		elapsed_xlogs,
-				elapsed_time;
-
-	Assert(ckpt_active);
-
-	/* Scale progress according to checkpoint_completion_target. */
-	progress *= CheckPointCompletionTarget;
-
-	/*
-	 * Check against the cached value first. Only do the more expensive
-	 * calculations once we reach the target previously calculated. Since
-	 * neither time or WAL insert pointer moves backwards, a freshly
-	 * calculated value can only be greater than or equal to the cached value.
-	 */
-	if (progress < ckpt_cached_elapsed)
-		return false;
-
-	/*
-	 * Check progress against WAL segments written and checkpoint_segments.
-	 *
-	 * We compare the current WAL insert location against the location
-	 * computed before calling CreateCheckPoint. The code in XLogInsert that
-	 * actually triggers a checkpoint when checkpoint_segments is exceeded
-	 * compares against RedoRecptr, so this is not completely accurate.
-	 * However, it's good enough for our purposes, we're only calculating an
-	 * estimate anyway.
-	 */
-	if (!RecoveryInProgress())
-	{
-		recptr = GetInsertRecPtr();
-		elapsed_xlogs =
-			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
-			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
-			CheckPointSegments;
-
-		if (progress < elapsed_xlogs)
-		{
-			ckpt_cached_elapsed = elapsed_xlogs;
-			return false;
-		}
-	}
-
-	/*
-	 * Check progress against time elapsed and checkpoint_timeout.
-	 */
-	gettimeofday(&now, NULL);
-	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
-					now.tv_usec / 1000000.0) / CheckPointTimeout;
-
-	if (progress < elapsed_time)
-	{
-		ckpt_cached_elapsed = elapsed_time;
-		return false;
-	}
-
-	/* It looks like we're on schedule. */
-	return true;
-}
-
-
 /* --------------------------------
  *		signal handler routines
  * --------------------------------
@@ -847,441 +359,9 @@ BgSigHupHandler(SIGNAL_ARGS)
 	got_SIGHUP = true;
 }
 
-/* SIGINT: set flag to run a normal checkpoint right away */
-static void
-ReqCheckpointHandler(SIGNAL_ARGS)
-{
-	checkpoint_requested = true;
-}
-
 /* SIGUSR2: set flag to run a shutdown checkpoint and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
 }
-
-
-/* --------------------------------
- *		communication with backends
- * --------------------------------
- */
-
-/*
- * BgWriterShmemSize
- *		Compute space needed for bgwriter-related shared memory
- */
-Size
-BgWriterShmemSize(void)
-{
-	Size		size;
-
-	/*
-	 * Currently, the size of the requests[] array is arbitrarily set equal to
-	 * NBuffers.  This may prove too large or small ...
-	 */
-	size = offsetof(BgWriterShmemStruct, requests);
-	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
-
-	return size;
-}
-
-/*
- * BgWriterShmemInit
- *		Allocate and initialize bgwriter-related shared memory
- */
-void
-BgWriterShmemInit(void)
-{
-	bool		found;
-
-	BgWriterShmem = (BgWriterShmemStruct *)
-		ShmemInitStruct("Background Writer Data",
-						BgWriterShmemSize(),
-						&found);
-
-	if (!found)
-	{
-		/* First time through, so initialize */
-		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
-		SpinLockInit(&BgWriterShmem->ckpt_lck);
-		BgWriterShmem->max_requests = NBuffers;
-	}
-}
-
-/*
- * RequestCheckpoint
- *		Called in backend processes to request a checkpoint
- *
- * flags is a bitwise OR of the following:
- *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
- *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
- *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
- *		ignoring checkpoint_completion_target parameter.
- *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
- *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
- *		CHECKPOINT_END_OF_RECOVERY).
- *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
- *		just signal bgwriter to do it, and return).
- *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
- *		(This affects logging, and in particular enables CheckPointWarning.)
- */
-void
-RequestCheckpoint(int flags)
-{
-	/* use volatile pointer to prevent code rearrangement */
-	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-	int			ntries;
-	int			old_failed,
-				old_started;
-
-	/*
-	 * If in a standalone backend, just do it ourselves.
-	 */
-	if (!IsPostmasterEnvironment)
-	{
-		/*
-		 * There's no point in doing slow checkpoints in a standalone backend,
-		 * because there's no other backends the checkpoint could disrupt.
-		 */
-		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
-
-		/*
-		 * After any checkpoint, close all smgr files.	This is so we won't
-		 * hang onto smgr references to deleted files indefinitely.
-		 */
-		smgrcloseall();
-
-		return;
-	}
-
-	/*
-	 * Atomically set the request flags, and take a snapshot of the counters.
-	 * When we see ckpt_started > old_started, we know the flags we set here
-	 * have been seen by bgwriter.
-	 *
-	 * Note that we OR the flags with any existing flags, to avoid overriding
-	 * a "stronger" request by another backend.  The flag senses must be
-	 * chosen to make this work!
-	 */
-	SpinLockAcquire(&bgs->ckpt_lck);
-
-	old_failed = bgs->ckpt_failed;
-	old_started = bgs->ckpt_started;
-	bgs->ckpt_flags |= flags;
-
-	SpinLockRelease(&bgs->ckpt_lck);
-
-	/*
-	 * Send signal to request checkpoint.  It's possible that the bgwriter
-	 * hasn't started yet, or is in process of restarting, so we will retry a
-	 * few times if needed.  Also, if not told to wait for the checkpoint to
-	 * occur, we consider failure to send the signal to be nonfatal and merely
-	 * LOG it.
-	 */
-	for (ntries = 0;; ntries++)
-	{
-		if (BgWriterShmem->bgwriter_pid == 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-				"could not request checkpoint because bgwriter not running");
-				break;
-			}
-		}
-		else if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-					 "could not signal for checkpoint: %m");
-				break;
-			}
-		}
-		else
-			break;				/* signal sent successfully */
-
-		CHECK_FOR_INTERRUPTS();
-		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
-	}
-
-	/*
-	 * If requested, wait for completion.  We detect completion according to
-	 * the algorithm given above.
-	 */
-	if (flags & CHECKPOINT_WAIT)
-	{
-		int			new_started,
-					new_failed;
-
-		/* Wait for a new checkpoint to start. */
-		for (;;)
-		{
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_started = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_started != old_started)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		/*
-		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
-		 */
-		for (;;)
-		{
-			int			new_done;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_done = bgs->ckpt_done;
-			new_failed = bgs->ckpt_failed;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_done - new_started >= 0)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		if (new_failed != old_failed)
-			ereport(ERROR,
-					(errmsg("checkpoint request failed"),
-					 errhint("Consult recent messages in the server log for details.")));
-	}
-}
-
-/*
- * ForwardFsyncRequest
- *		Forward a file-fsync request from a backend to the bgwriter
- *
- * Whenever a backend is compelled to write directly to a relation
- * (which should be seldom, if the bgwriter is getting its job done),
- * the backend calls this routine to pass over knowledge that the relation
- * is dirty and must be fsync'd before next checkpoint.  We also use this
- * opportunity to count such writes for statistical purposes.
- *
- * segno specifies which segment (not block!) of the relation needs to be
- * fsync'd.  (Since the valid range is much less than BlockNumber, we can
- * use high values for special flags; that's all internal to md.c, which
- * see for details.)
- *
- * To avoid holding the lock for longer than necessary, we normally write
- * to the requests[] queue without checking for duplicates.  The bgwriter
- * will have to eliminate dups internally anyway.  However, if we discover
- * that the queue is full, we make a pass over the entire queue to compact
- * it.	This is somewhat expensive, but the alternative is for the backend
- * to perform its own fsync, which is far more expensive in practice.  It
- * is theoretically possible a backend fsync might still be necessary, if
- * the queue is full and contains no duplicate entries.  In that case, we
- * let the backend know by returning false.
- */
-bool
-ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
-					BlockNumber segno)
-{
-	BgWriterRequest *request;
-
-	if (!IsUnderPostmaster)
-		return false;			/* probably shouldn't even get here */
-
-	if (am_bg_writer)
-		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
-
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Count all backend writes regardless of if they fit in the queue */
-	BgWriterShmem->num_backend_writes++;
-
-	/*
-	 * If the background writer isn't running or the request queue is full,
-	 * the backend will have to perform its own fsync request.	But before
-	 * forcing that to happen, we can try to compact the background writer
-	 * request queue.
-	 */
-	if (BgWriterShmem->bgwriter_pid == 0 ||
-		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
-		 && !CompactBgwriterRequestQueue()))
-	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		BgWriterShmem->num_backend_fsync++;
-		LWLockRelease(BgWriterCommLock);
-		return false;
-	}
-	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
-	request->rnode = rnode;
-	request->forknum = forknum;
-	request->segno = segno;
-	LWLockRelease(BgWriterCommLock);
-	return true;
-}
-
-/*
- * CompactBgwriterRequestQueue
- *		Remove duplicates from the request queue to avoid backend fsyncs.
- *
- * Although a full fsync request queue is not common, it can lead to severe
- * performance problems when it does happen.  So far, this situation has
- * only been observed to occur when the system is under heavy write load,
- * and especially during the "sync" phase of a checkpoint.	Without this
- * logic, each backend begins doing an fsync for every block written, which
- * gets very expensive and can slow down the whole system.
- *
- * Trying to do this every time the queue is full could lose if there
- * aren't any removable entries.  But should be vanishingly rare in
- * practice: there's one queue entry per shared buffer.
- */
-static bool
-CompactBgwriterRequestQueue()
-{
-	struct BgWriterSlotMapping
-	{
-		BgWriterRequest request;
-		int			slot;
-	};
-
-	int			n,
-				preserve_count;
-	int			num_skipped = 0;
-	HASHCTL		ctl;
-	HTAB	   *htab;
-	bool	   *skip_slot;
-
-	/* must hold BgWriterCommLock in exclusive mode */
-	Assert(LWLockHeldByMe(BgWriterCommLock));
-
-	/* Initialize temporary hash table */
-	MemSet(&ctl, 0, sizeof(ctl));
-	ctl.keysize = sizeof(BgWriterRequest);
-	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
-	ctl.hash = tag_hash;
-	htab = hash_create("CompactBgwriterRequestQueue",
-					   BgWriterShmem->num_requests,
-					   &ctl,
-					   HASH_ELEM | HASH_FUNCTION);
-
-	/* Initialize skip_slot array */
-	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
-
-	/*
-	 * The basic idea here is that a request can be skipped if it's followed
-	 * by a later, identical request.  It might seem more sensible to work
-	 * backwards from the end of the queue and check whether a request is
-	 * *preceded* by an earlier, identical request, in the hopes of doing less
-	 * copying.  But that might change the semantics, if there's an
-	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
-	 * we do it this way.  It would be possible to be even smarter if we made
-	 * the code below understand the specific semantics of such requests (it
-	 * could blow away preceding entries that would end up being canceled
-	 * anyhow), but it's not clear that the extra complexity would buy us
-	 * anything.
-	 */
-	for (n = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		BgWriterRequest *request;
-		struct BgWriterSlotMapping *slotmap;
-		bool		found;
-
-		request = &BgWriterShmem->requests[n];
-		slotmap = hash_search(htab, request, HASH_ENTER, &found);
-		if (found)
-		{
-			skip_slot[slotmap->slot] = true;
-			++num_skipped;
-		}
-		slotmap->slot = n;
-	}
-
-	/* Done with the hash table. */
-	hash_destroy(htab);
-
-	/* If no duplicates, we're out of luck. */
-	if (!num_skipped)
-	{
-		pfree(skip_slot);
-		return false;
-	}
-
-	/* We found some duplicates; remove them. */
-	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		if (skip_slot[n])
-			continue;
-		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
-	}
-	ereport(DEBUG1,
-	   (errmsg("compacted fsync request queue from %d entries to %d entries",
-			   BgWriterShmem->num_requests, preserve_count)));
-	BgWriterShmem->num_requests = preserve_count;
-
-	/* Cleanup. */
-	pfree(skip_slot);
-	return true;
-}
-
-/*
- * AbsorbFsyncRequests
- *		Retrieve queued fsync requests and pass them to local smgr.
- *
- * This is exported because it must be called during CreateCheckPoint;
- * we have to be sure we have accepted all pending requests just before
- * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
- * non-bgwriter processes, do nothing if not bgwriter.
- */
-void
-AbsorbFsyncRequests(void)
-{
-	BgWriterRequest *requests = NULL;
-	BgWriterRequest *request;
-	int			n;
-
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * We have to PANIC if we fail to absorb all the pending requests (eg,
-	 * because our hashtable runs out of memory).  This is because the system
-	 * cannot run safely if we are unable to fsync what we have been told to
-	 * fsync.  Fortunately, the hashtable is so small that the problem is
-	 * quite unlikely to arise in practice.
-	 */
-	START_CRIT_SECTION();
-
-	/*
-	 * We try to avoid holding the lock for a long time by copying the request
-	 * array.
-	 */
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Transfer write count into pending pgstats message */
-	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
-	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
-
-	BgWriterShmem->num_backend_writes = 0;
-	BgWriterShmem->num_backend_fsync = 0;
-
-	n = BgWriterShmem->num_requests;
-	if (n > 0)
-	{
-		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
-		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
-	}
-	BgWriterShmem->num_requests = 0;
-
-	LWLockRelease(BgWriterCommLock);
-
-	for (request = requests; n > 0; request++, n--)
-		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
-
-	if (requests)
-		pfree(requests);
-
-	END_CRIT_SECTION();
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
new file mode 100644
index 0000000..32eb191
--- /dev/null
+++ b/src/backend/postmaster/checkpointer.c
@@ -0,0 +1,1229 @@
+/*-------------------------------------------------------------------------
+ *
+ * checkpointer.c
+ *
+ * The checkpointer is new as of Postgres 9.2.  It handles all checkpoints.
+ * Checkpoints are automatically dispatched after a certain amount of time has
+ * elapsed since the last one, and it can be signaled to perform requested
+ * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
+ * so many WAL segments is implemented by having backends signal when they
+ * fill WAL segments; the checkpointer itself doesn't watch for the
+ * condition.)
+ *
+ * The checkpointer is started by the postmaster as soon as the startup subprocess
+ * finishes, or as soon as recovery begins if we are doing archive recovery.
+ * It remains alive until the postmaster commands it to terminate.
+ * Normal termination is by SIGUSR2, which instructs the checkpointer to execute
+ * a shutdown checkpoint and then exit(0).	(All backends must be stopped
+ * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * backend, the checkpointer will simply abort and exit on SIGQUIT.
+ *
+ * If the checkpointer exits unexpectedly, the postmaster treats that the same
+ * as a backend crash: shared memory may be corrupted, so remaining backends
+ * should be killed by SIGQUIT and then a recovery cycle started.  (Even if
+ * shared memory isn't corrupted, we have lost information about which
+ * files need to be fsync'd for the next checkpoint, and so a system
+ * restart needs to be forced.)
+ *
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/checkpointer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <signal.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "access/xlog_internal.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgwriter.h"
+#include "replication/syncrep.h"
+#include "storage/bufmgr.h"
+#include "storage/ipc.h"
+#include "storage/lwlock.h"
+#include "storage/pmsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+
+/*----------
+ * Shared memory area for communication between checkpointer and backends
+ *
+ * The ckpt counters allow backends to watch for completion of a checkpoint
+ * request they send.  Here's how it works:
+ *	* At start of a checkpoint, checkpointer reads (and clears) the request flags
+ *	  and increments ckpt_started, while holding ckpt_lck.
+ *	* On completion of a checkpoint, checkpointer sets ckpt_done to
+ *	  equal ckpt_started.
+ *	* On failure of a checkpoint, checkpointer increments ckpt_failed
+ *	  and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ *	1. Record current values of ckpt_failed and ckpt_started, and
+ *	   set request flags, while holding ckpt_lck.
+ *	2. Send signal to request checkpoint.
+ *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
+ *	   begun since you started this algorithm (although *not* that it was
+ *	   specifically initiated by your signal), and that it is using your flags.
+ *	4. Record new value of ckpt_started.
+ *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
+ *	   arithmetic here in case counters wrap around.)  Now you know a
+ *	   checkpoint has started and completed, but not whether it was
+ *	   successful.
+ *	6. If ckpt_failed is different from the originally saved value,
+ *	   assume request failed; otherwise it was definitely successful.
+ *
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start.  The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by non-bgwriter processes.  This counter should be wide enough that it
+ * can't overflow during a single bgwriter cycle.  num_backend_fsync
+ * counts the subset of those writes that also had to do their own fsync,
+ * because the background writer failed to absorb their request.
+ *
+ * The requests array holds fsync requests sent by backends and not yet
+ * absorbed by the checkpointer.
+ *
+ * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
+ * the requests fields are protected by BgWriterCommLock.
+ *----------
+ */
+typedef struct
+{
+	RelFileNodeBackend rnode;
+	ForkNumber	forknum;
+	BlockNumber segno;			/* see md.c for special values */
+	/* might add a real request-type field later; not needed yet */
+} BgWriterRequest;
+
+typedef struct
+{
+	pid_t		checkpointer_pid;	/* PID of bgwriter (0 if not started) */
+
+	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
+
+	int			ckpt_started;	/* advances when checkpoint starts */
+	int			ckpt_done;		/* advances when checkpoint done */
+	int			ckpt_failed;	/* advances when checkpoint fails */
+
+	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
+
+	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
+	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
+
+	int			num_requests;	/* current # of requests */
+	int			max_requests;	/* allocated array size */
+	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
+} BgWriterShmemStruct;
+
+static BgWriterShmemStruct *BgWriterShmem;
+
+/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB		1000
+
+/*
+ * GUC parameters
+ */
+int			CheckPointTimeout = 300;
+int			CheckPointWarning = 30;
+double		CheckPointCompletionTarget = 0.5;
+
+/*
+ * Flags set by interrupt handlers for later service in the main loop.
+ */
+static volatile sig_atomic_t got_SIGHUP = false;
+static volatile sig_atomic_t checkpoint_requested = false;
+static volatile sig_atomic_t shutdown_requested = false;
+
+/*
+ * Private state
+ */
+static bool am_checkpointer = false;
+
+static bool ckpt_active = false;
+
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void CheckArchiveTimeout(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+static bool CompactCheckpointerRequestQueue(void);
+
+/* Signal handlers */
+
+static void chkpt_quickdie(SIGNAL_ARGS);
+static void ChkptSigHupHandler(SIGNAL_ARGS);
+static void ReqCheckpointHandler(SIGNAL_ARGS);
+static void ReqShutdownHandler(SIGNAL_ARGS);
+
+
+/*
+ * Main entry point for checkpointer process
+ *
+ * This is invoked from BootstrapMain, which has already created the basic
+ * execution environment, but not enabled signals yet.
+ */
+void
+CheckpointerMain(void)
+{
+	sigjmp_buf	local_sigjmp_buf;
+	MemoryContext checkpointer_context;
+
+	BgWriterShmem->checkpointer_pid = MyProcPid;
+	am_checkpointer = true;
+
+	/*
+	 * If possible, make this process a group leader, so that the postmaster
+	 * can signal any child processes too.	(checkpointer probably never has any
+	 * child processes, but for consistency we make all postmaster child
+	 * processes do this.)
+	 */
+#ifdef HAVE_SETSID
+	if (setsid() < 0)
+		elog(FATAL, "setsid() failed: %m");
+#endif
+
+	/*
+	 * Properly accept or ignore signals the postmaster might send us
+	 *
+	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
+	 * system shutdown cycle, init will SIGTERM all processes at once.	We
+	 * want to wait for the backends to exit, whereupon the postmaster will
+	 * tell us it's okay to shut down (via SIGUSR2).
+	 *
+	 * SIGUSR1 is presently unused; keep it spare in case someday we want this
+	 * process to participate in ProcSignal signalling.
+	 */
+	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGINT, ReqCheckpointHandler);	/* request checkpoint */
+	pqsignal(SIGTERM, SIG_IGN);				/* ignore SIGTERM */
+	pqsignal(SIGQUIT, chkpt_quickdie);		/* hard crash time */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
+	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */
+
+	/*
+	 * Reset some signals that are accepted by postmaster but not here
+	 */
+	pqsignal(SIGCHLD, SIG_DFL);
+	pqsignal(SIGTTIN, SIG_DFL);
+	pqsignal(SIGTTOU, SIG_DFL);
+	pqsignal(SIGCONT, SIG_DFL);
+	pqsignal(SIGWINCH, SIG_DFL);
+
+	/* We allow SIGQUIT (quickdie) at all times */
+	sigdelset(&BlockSig, SIGQUIT);
+
+	/*
+	 * Initialize so that first time-driven event happens at the correct time.
+	 */
+	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
+
+	/*
+	 * Create a resource owner to keep track of our resources (currently only
+	 * buffer pins).
+	 */
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer");
+
+	/*
+	 * Create a memory context that we will do all our work in.  We do this so
+	 * that we can reset the context during error recovery and thereby avoid
+	 * possible memory leaks.  Formerly this code just ran in
+	 * TopMemoryContext, but resetting that would be a really bad idea.
+	 */
+	checkpointer_context = AllocSetContextCreate(TopMemoryContext,
+											 "Checkpointer",
+											 ALLOCSET_DEFAULT_MINSIZE,
+											 ALLOCSET_DEFAULT_INITSIZE,
+											 ALLOCSET_DEFAULT_MAXSIZE);
+	MemoryContextSwitchTo(checkpointer_context);
+
+	/*
+	 * If an exception is encountered, processing resumes here.
+	 *
+	 * See notes in postgres.c about the design of this coding.
+	 */
+	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
+	{
+		/* Since not using PG_TRY, must reset error stack by hand */
+		error_context_stack = NULL;
+
+		/* Prevent interrupts while cleaning up */
+		HOLD_INTERRUPTS();
+
+		/* Report the error to the server log */
+		EmitErrorReport();
+
+		/*
+		 * These operations are really just a minimal subset of
+		 * AbortTransaction().	We don't have very many resources to worry
+		 * about in checkpointer, but we do have LWLocks, buffers, and temp files.
+		 */
+		LWLockReleaseAll();
+		AbortBufferIO();
+		UnlockBuffers();
+		/* buffer pins are released here: */
+		ResourceOwnerRelease(CurrentResourceOwner,
+							 RESOURCE_RELEASE_BEFORE_LOCKS,
+							 false, true);
+		/* we needn't bother with the other ResourceOwnerRelease phases */
+		AtEOXact_Buffers(false);
+		AtEOXact_Files();
+		AtEOXact_HashTables(false);
+
+		/* Warn any waiting backends that the checkpoint failed. */
+		if (ckpt_active)
+		{
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_failed++;
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Now return to normal top-level context and clear ErrorContext for
+		 * next time.
+		 */
+		MemoryContextSwitchTo(checkpointer_context);
+		FlushErrorState();
+
+		/* Flush any leaked data in the top-level context */
+		MemoryContextResetAndDeleteChildren(checkpointer_context);
+
+		/* Now we can allow interrupts again */
+		RESUME_INTERRUPTS();
+
+		/*
+		 * Sleep at least 1 second after any error.  A write error is likely
+		 * to be repeated, and we don't want to be filling the error logs as
+		 * fast as we can.
+		 */
+		pg_usleep(1000000L);
+
+		/*
+		 * Close all open files after any error.  This is helpful on Windows,
+		 * where holding deleted files open causes various strange errors.
+		 * It's not clear we need it elsewhere, but shouldn't hurt.
+		 */
+		smgrcloseall();
+	}
+
+	/* We can now handle ereport(ERROR) */
+	PG_exception_stack = &local_sigjmp_buf;
+
+	/*
+	 * Unblock signals (they were blocked when the postmaster forked us)
+	 */
+	PG_SETMASK(&UnBlockSig);
+
+	/*
+	 * Use the recovery target timeline ID during recovery
+	 */
+	if (RecoveryInProgress())
+		ThisTimeLineID = GetRecoveryTargetTLI();
+
+	/* Do this once before starting the loop, then just at SIGHUP time. */
+	SyncRepUpdateSyncStandbysDefined();
+
+	/*
+	 * Loop forever
+	 */
+	for (;;)
+	{
+		bool		do_checkpoint = false;
+		int			flags = 0;
+		pg_time_t	now;
+		int			elapsed_secs;
+
+		/*
+		 * Emergency bailout if postmaster has died.  This is to avoid the
+		 * necessity for manual cleanup of all postmaster children.
+		 */
+		if (!PostmasterIsAlive())
+			exit(1);
+
+		/*
+		 * Process any requests or signals received recently.
+		 */
+		AbsorbFsyncRequests();
+
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+		if (checkpoint_requested)
+		{
+			checkpoint_requested = false;
+			do_checkpoint = true;
+			BgWriterStats.m_requested_checkpoints++;
+		}
+		if (shutdown_requested)
+		{
+			/*
+			 * From here on, elog(ERROR) should end with exit(1), not send
+			 * control back to the sigsetjmp block above
+			 */
+			ExitOnAnyError = true;
+			/* Close down the database */
+			ShutdownXLOG(0, 0);
+			/* Normal exit from the checkpointer is here */
+			proc_exit(0);		/* done */
+		}
+
+		/*
+		 * Force a checkpoint if too much time has elapsed since the last one.
+		 * Note that we count a timed checkpoint in stats only when this
+		 * occurs without an external request, but we set the CAUSE_TIME flag
+		 * bit even if there is also an external request.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+		{
+			if (!do_checkpoint)
+				BgWriterStats.m_timed_checkpoints++;
+			do_checkpoint = true;
+			flags |= CHECKPOINT_CAUSE_TIME;
+		}
+
+		/*
+		 * Do a checkpoint if requested.
+		 */
+		if (do_checkpoint)
+		{
+			bool		ckpt_performed = false;
+			bool		do_restartpoint;
+
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			/*
+			 * Check if we should perform a checkpoint or a restartpoint. As a
+			 * side-effect, RecoveryInProgress() initializes TimeLineID if
+			 * it's not set yet.
+			 */
+			do_restartpoint = RecoveryInProgress();
+
+			/*
+			 * Atomically fetch the request flags to figure out what kind of a
+			 * checkpoint we should perform, and increase the started-counter
+			 * to acknowledge that we've started a new checkpoint.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			flags |= bgs->ckpt_flags;
+			bgs->ckpt_flags = 0;
+			bgs->ckpt_started++;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			/*
+			 * The end-of-recovery checkpoint is a real checkpoint that's
+			 * performed while we're still in recovery.
+			 */
+			if (flags & CHECKPOINT_END_OF_RECOVERY)
+				do_restartpoint = false;
+
+			/*
+			 * We will warn if (a) too soon since last checkpoint (whatever
+			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+			 * since the last checkpoint start.  Note in particular that this
+			 * implementation will not generate warnings caused by
+			 * CheckPointTimeout < CheckPointWarning.
+			 */
+			if (!do_restartpoint &&
+				(flags & CHECKPOINT_CAUSE_XLOG) &&
+				elapsed_secs < CheckPointWarning)
+				ereport(LOG,
+						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+				"checkpoints are occurring too frequently (%d seconds apart)",
+									   elapsed_secs,
+									   elapsed_secs),
+						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
+
+			/*
+			 * Initialize checkpointer-private variables used during checkpoint.
+			 */
+			ckpt_active = true;
+			if (!do_restartpoint)
+				ckpt_start_recptr = GetInsertRecPtr();
+			ckpt_start_time = now;
+			ckpt_cached_elapsed = 0;
+
+			/*
+			 * Do the checkpoint.
+			 */
+			if (!do_restartpoint)
+			{
+				CreateCheckPoint(flags);
+				ckpt_performed = true;
+			}
+			else
+				ckpt_performed = CreateRestartPoint(flags);
+
+			/*
+			 * After any checkpoint, close all smgr files.	This is so we
+			 * won't hang onto smgr references to deleted files indefinitely.
+			 */
+			smgrcloseall();
+
+			/*
+			 * Indicate checkpoint completion to any waiting backends.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (ckpt_performed)
+			{
+				/*
+				 * Note we record the checkpoint start time not end time as
+				 * last_checkpoint_time.  This is so that time-driven
+				 * checkpoints happen at a predictable spacing.
+				 */
+				last_checkpoint_time = now;
+			}
+			else
+			{
+				/*
+				 * We were not able to perform the restartpoint (checkpoints
+				 * throw an ERROR in case of error).  Most likely because we
+				 * have not received any new checkpoint WAL records since the
+				 * last restartpoint. Try again in 15 s.
+				 */
+				last_checkpoint_time = now - CheckPointTimeout + 15;
+			}
+
+			ckpt_active = false;
+		}
+
+		/* Check for archive_timeout and switch xlog files if necessary. */
+		CheckArchiveTimeout();
+	}
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ *
+ * This will switch to a new WAL file and force an archive file write
+ * if any activity is recorded in the current WAL file, including just
+ * a single checkpoint record.
+ */
+static void
+CheckArchiveTimeout(void)
+{
+	pg_time_t	now;
+	pg_time_t	last_time;
+
+	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+		return;
+
+	now = (pg_time_t) time(NULL);
+
+	/* First we do a quick check using possibly-stale local state. */
+	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+		return;
+
+	/*
+	 * Update local state ... note that last_xlog_switch_time is the last time
+	 * a switch was performed *or requested*.
+	 */
+	last_time = GetLastSegSwitchTime();
+
+	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+	/* Now we can do the real check */
+	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+	{
+		XLogRecPtr	switchpoint;
+
+		/* OK, it's time to switch */
+		switchpoint = RequestXLogSwitch();
+
+		/*
+		 * If the returned pointer points exactly to a segment boundary,
+		 * assume nothing happened.
+		 */
+		if ((switchpoint.xrecoff % XLogSegSize) != 0)
+			ereport(DEBUG1,
+				(errmsg("transaction log switch forced (archive_timeout=%d)",
+						XLogArchiveTimeout)));
+
+		/*
+		 * Update state in any case, so we don't retry constantly when the
+		 * system is idle.
+		 */
+		last_xlog_switch_time = now;
+	}
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending.	(Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+	if (checkpoint_requested)
+	{
+		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+		/*
+		 * We don't need to acquire the ckpt_lck in this case because we're
+		 * only looking at a single flag bit.
+		 */
+		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * CheckpointWriteDelay -- control rate of checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for throttling BufferSync()'s write rate to hit
+ * checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+	static int	absorb_counter = WRITES_PER_ABSORB;
+
+	/* Do nothing if checkpoint is being executed by non-checkpointer process */
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * Perform the usual duties and take a nap, unless we're behind
+	 * schedule, in which case we just try to catch up as quickly as possible.
+	 */
+	if (!(flags & CHECKPOINT_IMMEDIATE) &&
+		!shutdown_requested &&
+		!ImmediateCheckpointRequested() &&
+		IsCheckpointOnSchedule(progress))
+	{
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+
+		CheckArchiveTimeout();
+
+		/*
+		 * Checkpoint sleep used to be connected to bgwriter_delay at 200ms.
+		 * That resulted in more frequent wakeups if not much work to do.
+		 * Checkpointer and bgwriter are no longer related so take the Big Sleep.
+		 */
+		pg_usleep(500000L);
+	}
+	else if (--absorb_counter <= 0)
+	{
+		/*
+		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+		 * operations even when we don't sleep, to prevent overflow of the
+		 * fsync request queue.
+		 */
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+	}
+}
+
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ *		 in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+	XLogRecPtr	recptr;
+	struct timeval now;
+	double		elapsed_xlogs,
+				elapsed_time;
+
+	Assert(ckpt_active);
+
+	/* Scale progress according to checkpoint_completion_target. */
+	progress *= CheckPointCompletionTarget;
+
+	/*
+	 * Check against the cached value first. Only do the more expensive
+	 * calculations once we reach the target previously calculated. Since
+	 * neither time or WAL insert pointer moves backwards, a freshly
+	 * calculated value can only be greater than or equal to the cached value.
+	 */
+	if (progress < ckpt_cached_elapsed)
+		return false;
+
+	/*
+	 * Check progress against WAL segments written and checkpoint_segments.
+	 *
+	 * We compare the current WAL insert location against the location
+	 * computed before calling CreateCheckPoint. The code in XLogInsert that
+	 * actually triggers a checkpoint when checkpoint_segments is exceeded
+	 * compares against RedoRecptr, so this is not completely accurate.
+	 * However, it's good enough for our purposes, we're only calculating an
+	 * estimate anyway.
+	 */
+	if (!RecoveryInProgress())
+	{
+		recptr = GetInsertRecPtr();
+		elapsed_xlogs =
+			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
+			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
+			CheckPointSegments;
+
+		if (progress < elapsed_xlogs)
+		{
+			ckpt_cached_elapsed = elapsed_xlogs;
+			return false;
+		}
+	}
+
+	/*
+	 * Check progress against time elapsed and checkpoint_timeout.
+	 */
+	gettimeofday(&now, NULL);
+	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+					now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+	if (progress < elapsed_time)
+	{
+		ckpt_cached_elapsed = elapsed_time;
+		return false;
+	}
+
+	/* It looks like we're on schedule. */
+	return true;
+}
+
+
+/* --------------------------------
+ *		signal handler routines
+ * --------------------------------
+ */
+
+/*
+ * chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
+ *
+ * Some backend has bought the farm,
+ * so we need to stop what we're doing and exit.
+ */
+static void
+chkpt_quickdie(SIGNAL_ARGS)
+{
+	PG_SETMASK(&BlockSig);
+
+	/*
+	 * We DO NOT want to run proc_exit() callbacks -- we're here because
+	 * shared memory may be corrupted, so we don't want to try to clean up our
+	 * transaction.  Just nail the windows shut and get out of town.  Now that
+	 * there's an atexit callback to prevent third-party code from breaking
+	 * things by calling exit() directly, we have to reset the callbacks
+	 * explicitly to make this work as intended.
+	 */
+	on_exit_reset();
+
+	/*
+	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
+	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
+	 * backend.  This is necessary precisely because we don't clean up our
+	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
+	 * should ensure the postmaster sees this as a crash, too, but no harm in
+	 * being doubly sure.)
+	 */
+	exit(2);
+}
+
+/* SIGHUP: set flag to re-read config file at next convenient time */
+static void
+ChkptSigHupHandler(SIGNAL_ARGS)
+{
+	got_SIGHUP = true;
+}
+
+/* SIGINT: set flag to run a normal checkpoint right away */
+static void
+ReqCheckpointHandler(SIGNAL_ARGS)
+{
+	checkpoint_requested = true;
+}
+
+/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
+static void
+ReqShutdownHandler(SIGNAL_ARGS)
+{
+	shutdown_requested = true;
+}
+
+
+/* --------------------------------
+ *		communication with backends
+ * --------------------------------
+ */
+
+/*
+ * BgWriterShmemSize
+ *		Compute space needed for bgwriter-related shared memory
+ */
+Size
+BgWriterShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Currently, the size of the requests[] array is arbitrarily set equal to
+	 * NBuffers.  This may prove too large or small ...
+	 */
+	size = offsetof(BgWriterShmemStruct, requests);
+	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
+
+	return size;
+}
+
+/*
+ * BgWriterShmemInit
+ *		Allocate and initialize bgwriter-related shared memory
+ */
+void
+BgWriterShmemInit(void)
+{
+	bool		found;
+
+	BgWriterShmem = (BgWriterShmemStruct *)
+		ShmemInitStruct("Background Writer Data",
+						BgWriterShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
+		SpinLockInit(&BgWriterShmem->ckpt_lck);
+		BgWriterShmem->max_requests = NBuffers;
+	}
+}
+
+/*
+ * RequestCheckpoint
+ *		Called in backend processes to request a checkpoint
+ *
+ * flags is a bitwise OR of the following:
+ *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ *		ignoring checkpoint_completion_target parameter.
+ *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
+ *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ *		CHECKPOINT_END_OF_RECOVERY).
+ *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ *		just signal bgwriter to do it, and return).
+ *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ *		(This affects logging, and in particular enables CheckPointWarning.)
+ */
+void
+RequestCheckpoint(int flags)
+{
+	/* use volatile pointer to prevent code rearrangement */
+	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+	int			ntries;
+	int			old_failed,
+				old_started;
+
+	/*
+	 * If in a standalone backend, just do it ourselves.
+	 */
+	if (!IsPostmasterEnvironment)
+	{
+		/*
+		 * There's no point in doing slow checkpoints in a standalone backend,
+		 * because there's no other backends the checkpoint could disrupt.
+		 */
+		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
+
+		/*
+		 * After any checkpoint, close all smgr files.	This is so we won't
+		 * hang onto smgr references to deleted files indefinitely.
+		 */
+		smgrcloseall();
+
+		return;
+	}
+
+	/*
+	 * Atomically set the request flags, and take a snapshot of the counters.
+	 * When we see ckpt_started > old_started, we know the flags we set here
+	 * have been seen by bgwriter.
+	 *
+	 * Note that we OR the flags with any existing flags, to avoid overriding
+	 * a "stronger" request by another backend.  The flag senses must be
+	 * chosen to make this work!
+	 */
+	SpinLockAcquire(&bgs->ckpt_lck);
+
+	old_failed = bgs->ckpt_failed;
+	old_started = bgs->ckpt_started;
+	bgs->ckpt_flags |= flags;
+
+	SpinLockRelease(&bgs->ckpt_lck);
+
+	/*
+	 * Send signal to request checkpoint.  It's possible that the bgwriter
+	 * hasn't started yet, or is in process of restarting, so we will retry a
+	 * few times if needed.  Also, if not told to wait for the checkpoint to
+	 * occur, we consider failure to send the signal to be nonfatal and merely
+	 * LOG it.
+	 */
+	for (ntries = 0;; ntries++)
+	{
+		if (BgWriterShmem->checkpointer_pid == 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+				"could not request checkpoint because bgwriter not running");
+				break;
+			}
+		}
+		else if (kill(BgWriterShmem->checkpointer_pid, SIGINT) != 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: %m");
+				break;
+			}
+		}
+		else
+			break;				/* signal sent successfully */
+
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
+	}
+
+	/*
+	 * If requested, wait for completion.  We detect completion according to
+	 * the algorithm given above.
+	 */
+	if (flags & CHECKPOINT_WAIT)
+	{
+		int			new_started,
+					new_failed;
+
+		/* Wait for a new checkpoint to start. */
+		for (;;)
+		{
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_started = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_started != old_started)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		/*
+		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
+		 */
+		for (;;)
+		{
+			int			new_done;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_done = bgs->ckpt_done;
+			new_failed = bgs->ckpt_failed;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_done - new_started >= 0)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		if (new_failed != old_failed)
+			ereport(ERROR,
+					(errmsg("checkpoint request failed"),
+					 errhint("Consult recent messages in the server log for details.")));
+	}
+}
+
+/*
+ * ForwardFsyncRequest
+ *		Forward a file-fsync request from a backend to the bgwriter
+ *
+ * Whenever a backend is compelled to write directly to a relation
+ * (which should be seldom, if the bgwriter is getting its job done),
+ * the backend calls this routine to pass over knowledge that the relation
+ * is dirty and must be fsync'd before next checkpoint.  We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * segno specifies which segment (not block!) of the relation needs to be
+ * fsync'd.  (Since the valid range is much less than BlockNumber, we can
+ * use high values for special flags; that's all internal to md.c, which
+ * see for details.)
+ *
+ * To avoid holding the lock for longer than necessary, we normally write
+ * to the requests[] queue without checking for duplicates.  The bgwriter
+ * will have to eliminate dups internally anyway.  However, if we discover
+ * that the queue is full, we make a pass over the entire queue to compact
+ * it.	This is somewhat expensive, but the alternative is for the backend
+ * to perform its own fsync, which is far more expensive in practice.  It
+ * is theoretically possible a backend fsync might still be necessary, if
+ * the queue is full and contains no duplicate entries.  In that case, we
+ * let the backend know by returning false.
+ */
+bool
+ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
+					BlockNumber segno)
+{
+	BgWriterRequest *request;
+
+	if (!IsUnderPostmaster)
+		return false;			/* probably shouldn't even get here */
+
+	if (am_checkpointer)
+		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
+
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Count all backend writes regardless of if they fit in the queue */
+	BgWriterShmem->num_backend_writes++;
+
+	/*
+	 * If the background writer isn't running or the request queue is full,
+	 * the backend will have to perform its own fsync request.	But before
+	 * forcing that to happen, we can try to compact the background writer
+	 * request queue.
+	 */
+	if (BgWriterShmem->checkpointer_pid == 0 ||
+		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
+		 && !CompactCheckpointerRequestQueue()))
+	{
+		/*
+		 * Count the subset of writes where backends have to do their own
+		 * fsync
+		 */
+		BgWriterShmem->num_backend_fsync++;
+		LWLockRelease(BgWriterCommLock);
+		return false;
+	}
+	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
+	request->rnode = rnode;
+	request->forknum = forknum;
+	request->segno = segno;
+	LWLockRelease(BgWriterCommLock);
+	return true;
+}
+
+/*
+ * CompactCheckpointerRequestQueue
+ *		Remove duplicates from the request queue to avoid backend fsyncs.
+ *
+ * Although a full fsync request queue is not common, it can lead to severe
+ * performance problems when it does happen.  So far, this situation has
+ * only been observed to occur when the system is under heavy write load,
+ * and especially during the "sync" phase of a checkpoint.	Without this
+ * logic, each backend begins doing an fsync for every block written, which
+ * gets very expensive and can slow down the whole system.
+ *
+ * Trying to do this every time the queue is full could lose if there
+ * aren't any removable entries.  But should be vanishingly rare in
+ * practice: there's one queue entry per shared buffer.
+ */
+static bool
+CompactCheckpointerRequestQueue()
+{
+	struct BgWriterSlotMapping
+	{
+		BgWriterRequest request;
+		int			slot;
+	};
+
+	int			n,
+				preserve_count;
+	int			num_skipped = 0;
+	HASHCTL		ctl;
+	HTAB	   *htab;
+	bool	   *skip_slot;
+
+	/* must hold BgWriterCommLock in exclusive mode */
+	Assert(LWLockHeldByMe(BgWriterCommLock));
+
+	/* Initialize temporary hash table */
+	MemSet(&ctl, 0, sizeof(ctl));
+	ctl.keysize = sizeof(BgWriterRequest);
+	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
+	ctl.hash = tag_hash;
+	htab = hash_create("CompactBgwriterRequestQueue",
+					   BgWriterShmem->num_requests,
+					   &ctl,
+					   HASH_ELEM | HASH_FUNCTION);
+
+	/* Initialize skip_slot array */
+	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
+
+	/*
+	 * The basic idea here is that a request can be skipped if it's followed
+	 * by a later, identical request.  It might seem more sensible to work
+	 * backwards from the end of the queue and check whether a request is
+	 * *preceded* by an earlier, identical request, in the hopes of doing less
+	 * copying.  But that might change the semantics, if there's an
+	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
+	 * we do it this way.  It would be possible to be even smarter if we made
+	 * the code below understand the specific semantics of such requests (it
+	 * could blow away preceding entries that would end up being canceled
+	 * anyhow), but it's not clear that the extra complexity would buy us
+	 * anything.
+	 */
+	for (n = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		BgWriterRequest *request;
+		struct BgWriterSlotMapping *slotmap;
+		bool		found;
+
+		request = &BgWriterShmem->requests[n];
+		slotmap = hash_search(htab, request, HASH_ENTER, &found);
+		if (found)
+		{
+			skip_slot[slotmap->slot] = true;
+			++num_skipped;
+		}
+		slotmap->slot = n;
+	}
+
+	/* Done with the hash table. */
+	hash_destroy(htab);
+
+	/* If no duplicates, we're out of luck. */
+	if (!num_skipped)
+	{
+		pfree(skip_slot);
+		return false;
+	}
+
+	/* We found some duplicates; remove them. */
+	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		if (skip_slot[n])
+			continue;
+		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
+	}
+	ereport(DEBUG1,
+	   (errmsg("compacted fsync request queue from %d entries to %d entries",
+			   BgWriterShmem->num_requests, preserve_count)));
+	BgWriterShmem->num_requests = preserve_count;
+
+	/* Cleanup. */
+	pfree(skip_slot);
+	return true;
+}
+
+/*
+ * AbsorbFsyncRequests
+ *		Retrieve queued fsync requests and pass them to local smgr.
+ *
+ * This is exported because it must be called during CreateCheckPoint;
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
+ * non-checkpointer processes, do nothing if not checkpointer.
+ */
+void
+AbsorbFsyncRequests(void)
+{
+	BgWriterRequest *requests = NULL;
+	BgWriterRequest *request;
+	int			n;
+
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * We have to PANIC if we fail to absorb all the pending requests (eg,
+	 * because our hashtable runs out of memory).  This is because the system
+	 * cannot run safely if we are unable to fsync what we have been told to
+	 * fsync.  Fortunately, the hashtable is so small that the problem is
+	 * quite unlikely to arise in practice.
+	 */
+	START_CRIT_SECTION();
+
+	/*
+	 * We try to avoid holding the lock for a long time by copying the request
+	 * array.
+	 */
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Transfer write count into pending pgstats message */
+	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
+	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
+
+	BgWriterShmem->num_backend_writes = 0;
+	BgWriterShmem->num_backend_fsync = 0;
+
+	n = BgWriterShmem->num_requests;
+	if (n > 0)
+	{
+		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
+		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
+	}
+	BgWriterShmem->num_requests = 0;
+
+	LWLockRelease(BgWriterCommLock);
+
+	for (request = requests; n > 0; request++, n--)
+		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
+
+	if (requests)
+		pfree(requests);
+
+	END_CRIT_SECTION();
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 0a84d97..c8599c2 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -206,6 +206,7 @@ bool		restart_after_crash = true;
 /* PIDs of special child processes; 0 when not running */
 static pid_t StartupPID = 0,
 			BgWriterPID = 0,
+			CheckpointerPID = 0,
 			WalWriterPID = 0,
 			WalReceiverPID = 0,
 			AutoVacPID = 0,
@@ -277,7 +278,7 @@ typedef enum
 	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
 	PM_WAIT_READONLY,			/* waiting for read only backends to exit */
 	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
-	PM_SHUTDOWN,				/* waiting for bgwriter to do shutdown ckpt */
+	PM_SHUTDOWN,				/* waiting for checkpointer to do shutdown ckpt */
 	PM_SHUTDOWN_2,				/* waiting for archiver and walsenders to
 								 * finish */
 	PM_WAIT_DEAD_END,			/* waiting for dead_end children to exit */
@@ -463,6 +464,7 @@ static void ShmemBackendArrayRemove(Backend *bn);
 
 #define StartupDataBase()		StartChildProcess(StartupProcess)
 #define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
+#define StartCheckpointer()		StartChildProcess(CheckpointerProcess)
 #define StartWalWriter()		StartChildProcess(WalWriterProcess)
 #define StartWalReceiver()		StartChildProcess(WalReceiverProcess)
 
@@ -1015,8 +1017,8 @@ PostmasterMain(int argc, char *argv[])
 	 * CAUTION: when changing this list, check for side-effects on the signal
 	 * handling setup of child processes.  See tcop/postgres.c,
 	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
-	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c, and
-	 * postmaster/syslogger.c.
+	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
+	 * postmaster/syslogger.c and postmaster/checkpointer.c
 	 */
 	pqinitmask();
 	PG_SETMASK(&BlockSig);
@@ -1353,10 +1355,14 @@ ServerLoop(void)
 		 * state that prevents it, start one.  It doesn't matter if this
 		 * fails, we'll just try again later.
 		 */
-		if (BgWriterPID == 0 &&
-			(pmState == PM_RUN || pmState == PM_RECOVERY ||
-			 pmState == PM_HOT_STANDBY))
-			BgWriterPID = StartBackgroundWriter();
+		if (pmState == PM_RUN || pmState == PM_RECOVERY ||
+			 pmState == PM_HOT_STANDBY)
+		{
+			if (BgWriterPID == 0)
+				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
+		}
 
 		/*
 		 * Likewise, if we have lost the walwriter process, try to start a new
@@ -2034,6 +2040,8 @@ SIGHUP_handler(SIGNAL_ARGS)
 			signal_child(StartupPID, SIGHUP);
 		if (BgWriterPID != 0)
 			signal_child(BgWriterPID, SIGHUP);
+		if (CheckpointerPID != 0)
+			signal_child(CheckpointerPID, SIGHUP);
 		if (WalWriterPID != 0)
 			signal_child(WalWriterPID, SIGHUP);
 		if (WalReceiverPID != 0)
@@ -2148,7 +2156,7 @@ pmdie(SIGNAL_ARGS)
 				signal_child(WalReceiverPID, SIGTERM);
 			if (pmState == PM_RECOVERY)
 			{
-				/* only bgwriter is active in this state */
+				/* only checkpointer is active in this state */
 				pmState = PM_WAIT_BACKENDS;
 			}
 			else if (pmState == PM_RUN ||
@@ -2193,6 +2201,8 @@ pmdie(SIGNAL_ARGS)
 				signal_child(StartupPID, SIGQUIT);
 			if (BgWriterPID != 0)
 				signal_child(BgWriterPID, SIGQUIT);
+			if (CheckpointerPID != 0)
+				signal_child(CheckpointerPID, SIGQUIT);
 			if (WalWriterPID != 0)
 				signal_child(WalWriterPID, SIGQUIT);
 			if (WalReceiverPID != 0)
@@ -2323,12 +2333,14 @@ reaper(SIGNAL_ARGS)
 			}
 
 			/*
-			 * Crank up the background writer, if we didn't do that already
+			 * Crank up background tasks, if we didn't do that already
 			 * when we entered consistent recovery state.  It doesn't matter
 			 * if this fails, we'll just try again later.
 			 */
 			if (BgWriterPID == 0)
 				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
 
 			/*
 			 * Likewise, start other special children as needed.  In a restart
@@ -2356,10 +2368,22 @@ reaper(SIGNAL_ARGS)
 		if (pid == BgWriterPID)
 		{
 			BgWriterPID = 0;
+			if (!EXIT_STATUS_0(exitstatus))
+				HandleChildCrash(pid, exitstatus,
+								 _("background writer process"));
+			continue;
+		}
+
+		/*
+		 * Was it the checkpointer?
+		 */
+		if (pid == CheckpointerPID)
+		{
+			CheckpointerPID = 0;
 			if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
 			{
 				/*
-				 * OK, we saw normal exit of the bgwriter after it's been told
+				 * OK, we saw normal exit of the checkpointer after it's been told
 				 * to shut down.  We expect that it wrote a shutdown
 				 * checkpoint.	(If for some reason it didn't, recovery will
 				 * occur on next postmaster start.)
@@ -2396,11 +2420,11 @@ reaper(SIGNAL_ARGS)
 			else
 			{
 				/*
-				 * Any unexpected exit of the bgwriter (including FATAL exit)
+				 * Any unexpected exit of the checkpointer (including FATAL exit)
 				 * is treated as a crash.
 				 */
 				HandleChildCrash(pid, exitstatus,
-								 _("background writer process"));
+								 _("checkpointer process"));
 			}
 
 			continue;
@@ -2584,8 +2608,8 @@ CleanupBackend(int pid,
 }
 
 /*
- * HandleChildCrash -- cleanup after failed backend, bgwriter, walwriter,
- * or autovacuum.
+ * HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
+ * walwriter or autovacuum.
  *
  * The objectives here are to clean up our local state about the child
  * process, and to signal all other remaining children to quickdie.
@@ -2678,6 +2702,18 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 		signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
 	}
 
+	/* Take care of the checkpointer too */
+	if (pid == CheckpointerPID)
+		CheckpointerPID = 0;
+	else if (CheckpointerPID != 0 && !FatalError)
+	{
+		ereport(DEBUG2,
+				(errmsg_internal("sending %s to process %d",
+								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
+								 (int) CheckpointerPID)));
+		signal_child(CheckpointerPID, (SendStop ? SIGSTOP : SIGQUIT));
+	}
+
 	/* Take care of the walwriter too */
 	if (pid == WalWriterPID)
 		WalWriterPID = 0;
@@ -2857,9 +2893,10 @@ PostmasterStateMachine(void)
 	{
 		/*
 		 * PM_WAIT_BACKENDS state ends when we have no regular backends
-		 * (including autovac workers) and no walwriter or autovac launcher.
-		 * If we are doing crash recovery then we expect the bgwriter to exit
-		 * too, otherwise not.	The archiver, stats, and syslogger processes
+		 * (including autovac workers) and no walwriter, autovac launcher
+		 * or bgwriter.  If we are doing crash recovery then we expect the
+		 * checkpointer to exit as well, otherwise not.
+		 * The archiver, stats, and syslogger processes
 		 * are disregarded since they are not connected to shared memory; we
 		 * also disregard dead_end children here. Walsenders are also
 		 * disregarded, they will be terminated later after writing the
@@ -2868,7 +2905,8 @@ PostmasterStateMachine(void)
 		if (CountChildren(BACKEND_TYPE_NORMAL | BACKEND_TYPE_AUTOVAC) == 0 &&
 			StartupPID == 0 &&
 			WalReceiverPID == 0 &&
-			(BgWriterPID == 0 || !FatalError) &&
+			BgWriterPID == 0 &&
+			(CheckpointerPID == 0 || !FatalError) &&
 			WalWriterPID == 0 &&
 			AutoVacPID == 0)
 		{
@@ -2890,22 +2928,22 @@ PostmasterStateMachine(void)
 				/*
 				 * If we get here, we are proceeding with normal shutdown. All
 				 * the regular children are gone, and it's time to tell the
-				 * bgwriter to do a shutdown checkpoint.
+				 * checkpointer to do a shutdown checkpoint.
 				 */
 				Assert(Shutdown > NoShutdown);
-				/* Start the bgwriter if not running */
-				if (BgWriterPID == 0)
-					BgWriterPID = StartBackgroundWriter();
+				/* Start the checkpointer if not running */
+				if (CheckpointerPID == 0)
+					CheckpointerPID = StartCheckpointer();
 				/* And tell it to shut down */
-				if (BgWriterPID != 0)
+				if (CheckpointerPID != 0)
 				{
-					signal_child(BgWriterPID, SIGUSR2);
+					signal_child(CheckpointerPID, SIGUSR2);
 					pmState = PM_SHUTDOWN;
 				}
 				else
 				{
 					/*
-					 * If we failed to fork a bgwriter, just shut down. Any
+					 * If we failed to fork a checkpointer, just shut down. Any
 					 * required cleanup will happen at next restart. We set
 					 * FatalError so that an "abnormal shutdown" message gets
 					 * logged when we exit.
@@ -2964,6 +3002,7 @@ PostmasterStateMachine(void)
 			Assert(StartupPID == 0);
 			Assert(WalReceiverPID == 0);
 			Assert(BgWriterPID == 0);
+			Assert(CheckpointerPID == 0);
 			Assert(WalWriterPID == 0);
 			Assert(AutoVacPID == 0);
 			/* syslogger is not considered here */
@@ -4143,6 +4182,8 @@ sigusr1_handler(SIGNAL_ARGS)
 		 */
 		Assert(BgWriterPID == 0);
 		BgWriterPID = StartBackgroundWriter();
+		Assert(CheckpointerPID == 0);
+		CheckpointerPID = StartCheckpointer();
 
 		pmState = PM_RECOVERY;
 	}
@@ -4429,6 +4470,10 @@ StartChildProcess(AuxProcType type)
 				ereport(LOG,
 				   (errmsg("could not fork background writer process: %m")));
 				break;
+			case CheckpointerProcess:
+				ereport(LOG,
+				   (errmsg("could not fork checkpointer process: %m")));
+				break;
 			case WalWriterProcess:
 				ereport(LOG,
 						(errmsg("could not fork WAL writer process: %m")));
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8647edd..184e820 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1278,11 +1278,9 @@ BufferSync(int flags)
 					break;
 
 				/*
-				 * Perform normal bgwriter duties and sleep to throttle our
-				 * I/O rate.
+				 * Sleep to throttle our I/O rate.
 				 */
-				CheckpointWriteDelay(flags,
-									 (double) num_written / num_to_write);
+				CheckpointWriteDelay(flags, (double) num_written / num_to_write);
 			}
 		}
 
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 3015885..a761369 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -38,7 +38,7 @@
 /*
  * Special values for the segno arg to RememberFsyncRequest.
  *
- * Note that CompactBgwriterRequestQueue assumes that it's OK to remove an
+ * Note that CompactcheckpointerRequestQueue assumes that it's OK to remove an
  * fsync request from the queue if an identical, subsequent request is found.
  * See comments there before making changes here.
  */
@@ -77,7 +77,7 @@
  *	Inactive segments are those that once contained data but are currently
  *	not needed because of an mdtruncate() operation.  The reason for leaving
  *	them present at size zero, rather than unlinking them, is that other
- *	backends and/or the bgwriter might be holding open file references to
+ *	backends and/or the checkpointer might be holding open file references to
  *	such segments.	If the relation expands again after mdtruncate(), such
  *	that a deactivated segment becomes active again, it is important that
  *	such file references still be valid --- else data might get written
@@ -111,7 +111,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
 
 
 /*
- * In some contexts (currently, standalone backends and the bgwriter process)
+ * In some contexts (currently, standalone backends and the checkpointer process)
  * we keep track of pending fsync operations: we need to remember all relation
  * segments that have been written since the last checkpoint, so that we can
  * fsync them down to disk before completing the next checkpoint.  This hash
@@ -123,7 +123,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
  * a hash table, because we don't expect there to be any duplicate requests.
  *
  * (Regular backends do not track pending operations locally, but forward
- * them to the bgwriter.)
+ * them to the checkpointer.)
  */
 typedef struct
 {
@@ -194,7 +194,7 @@ mdinit(void)
 	 * Create pending-operations hashtable if we need it.  Currently, we need
 	 * it if we are standalone (not under a postmaster) OR if we are a
 	 * bootstrap-mode subprocess of a postmaster (that is, a startup or
-	 * bgwriter process).
+	 * checkpointer process).
 	 */
 	if (!IsUnderPostmaster || IsBootstrapProcessingMode())
 	{
@@ -214,10 +214,10 @@ mdinit(void)
 }
 
 /*
- * In archive recovery, we rely on bgwriter to do fsyncs, but we will have
+ * In archive recovery, we rely on checkpointer to do fsyncs, but we will have
  * already created the pendingOpsTable during initialization of the startup
  * process.  Calling this function drops the local pendingOpsTable so that
- * subsequent requests will be forwarded to bgwriter.
+ * subsequent requests will be forwarded to checkpointer.
  */
 void
 SetForwardFsyncRequests(void)
@@ -765,9 +765,9 @@ mdnblocks(SMgrRelation reln, ForkNumber forknum)
 	 * NOTE: this assumption could only be wrong if another backend has
 	 * truncated the relation.	We rely on higher code levels to handle that
 	 * scenario by closing and re-opening the md fd, which is handled via
-	 * relcache flush.	(Since the bgwriter doesn't participate in relcache
+	 * relcache flush.	(Since the checkpointer doesn't participate in relcache
 	 * flush, it could have segment chain entries for inactive segments;
-	 * that's OK because the bgwriter never needs to compute relation size.)
+	 * that's OK because the checkpointer never needs to compute relation size.)
 	 */
 	while (v->mdfd_chain != NULL)
 	{
@@ -957,7 +957,7 @@ mdsync(void)
 		elog(ERROR, "cannot sync without a pendingOpsTable");
 
 	/*
-	 * If we are in the bgwriter, the sync had better include all fsync
+	 * If we are in the checkpointer, the sync had better include all fsync
 	 * requests that were queued by backends up to this point.	The tightest
 	 * race condition that could occur is that a buffer that must be written
 	 * and fsync'd for the checkpoint could have been dumped by a backend just
@@ -1033,7 +1033,7 @@ mdsync(void)
 			int			failures;
 
 			/*
-			 * If in bgwriter, we want to absorb pending requests every so
+			 * If in checkpointer, we want to absorb pending requests every so
 			 * often to prevent overflow of the fsync request queue.  It is
 			 * unspecified whether newly-added entries will be visited by
 			 * hash_seq_search, but we don't care since we don't need to
@@ -1070,9 +1070,9 @@ mdsync(void)
 				 * say "but an unreferenced SMgrRelation is still a leak!" Not
 				 * really, because the only case in which a checkpoint is done
 				 * by a process that isn't about to shut down is in the
-				 * bgwriter, and it will periodically do smgrcloseall(). This
+				 * checkpointer, and it will periodically do smgrcloseall(). This
 				 * fact justifies our not closing the reln in the success path
-				 * either, which is a good thing since in non-bgwriter cases
+				 * either, which is a good thing since in non-checkpointer cases
 				 * we couldn't safely do that.)  Furthermore, in many cases
 				 * the relation will have been dirtied through this same smgr
 				 * relation, and so we can save a file open/close cycle.
@@ -1301,7 +1301,7 @@ register_unlink(RelFileNodeBackend rnode)
 	else
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the request
+		 * Notify the checkpointer about it.  If we fail to queue the request
 		 * message, we have to sleep and try again, because we can't simply
 		 * delete the file now.  Ugly, but hopefully won't happen often.
 		 *
@@ -1315,10 +1315,10 @@ register_unlink(RelFileNodeBackend rnode)
 }
 
 /*
- * RememberFsyncRequest() -- callback from bgwriter side of fsync request
+ * RememberFsyncRequest() -- callback from checkpointer side of fsync request
  *
  * We stuff most fsync requests into the local hash table for execution
- * during the bgwriter's next checkpoint.  UNLINK requests go into a
+ * during the checkpointer's next checkpoint.  UNLINK requests go into a
  * separate linked list, however, because they get processed separately.
  *
  * The range of possible segment numbers is way less than the range of
@@ -1460,20 +1460,20 @@ ForgetRelationFsyncRequests(RelFileNodeBackend rnode, ForkNumber forknum)
 	else if (IsUnderPostmaster)
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the revoke
+		 * Notify the checkpointer about it.  If we fail to queue the revoke
 		 * message, we have to sleep and try again ... ugly, but hopefully
 		 * won't happen often.
 		 *
 		 * XXX should we CHECK_FOR_INTERRUPTS in this loop?  Escaping with an
 		 * error would leave the no-longer-used file still present on disk,
-		 * which would be bad, so I'm inclined to assume that the bgwriter
+		 * which would be bad, so I'm inclined to assume that the checkpointer
 		 * will always empty the queue soon.
 		 */
 		while (!ForwardFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC))
 			pg_usleep(10000L);	/* 10 msec seems a good number */
 
 		/*
-		 * Note we don't wait for the bgwriter to actually absorb the revoke
+		 * Note we don't wait for the checkpointer to actually absorb the revoke
 		 * message; see mdsync() for the implications.
 		 */
 	}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 4eaa243..cb43879 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -256,7 +256,7 @@ typedef struct RmgrData
 extern const RmgrData RmgrTable[];
 
 /*
- * Exported to support xlog switching from bgwriter
+ * Exported to support xlog switching from checkpointer
  */
 extern pg_time_t GetLastSegSwitchTime(void);
 extern XLogRecPtr RequestXLogSwitch(void);
diff --git a/src/include/bootstrap/bootstrap.h b/src/include/bootstrap/bootstrap.h
index cee9bd1..6153b7a 100644
--- a/src/include/bootstrap/bootstrap.h
+++ b/src/include/bootstrap/bootstrap.h
@@ -22,6 +22,7 @@ typedef enum
 	BootstrapProcess,
 	StartupProcess,
 	BgWriterProcess,
+	CheckpointerProcess,
 	WalWriterProcess,
 	WalReceiverProcess,
 
diff --git a/src/include/postmaster/bgwriter.h b/src/include/postmaster/bgwriter.h
index eaf2206..c05901e 100644
--- a/src/include/postmaster/bgwriter.h
+++ b/src/include/postmaster/bgwriter.h
@@ -23,6 +23,7 @@ extern int	CheckPointWarning;
 extern double CheckPointCompletionTarget;
 
 extern void BackgroundWriterMain(void);
+extern void CheckpointerMain(void);
 
 extern void RequestCheckpoint(int flags);
 extern void CheckpointWriteDelay(int flags, double progress);
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 46ec625..6e798b1 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -190,11 +190,11 @@ extern PROC_HDR *ProcGlobal;
  * We set aside some extra PGPROC structures for auxiliary processes,
  * ie things that aren't full-fledged backends but need shmem access.
  *
- * Background writer and WAL writer run during normal operation. Startup
- * process and WAL receiver also consume 2 slots, but WAL writer is
- * launched only after startup has exited, so we only need 3 slots.
+ * Background writer, checkpointer and WAL writer run during normal operation.
+ * Startup process and WAL receiver also consume 2 slots, but WAL writer is
+ * launched only after startup has exited, so we only need 4 slots.
  */
-#define NUM_AUXILIARY_PROCS		3
+#define NUM_AUXILIARY_PROCS		4
 
 
 /* configurable options */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 2a27e0b..d5afe01 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -19,7 +19,7 @@
 
 /*
  * Reasons for signalling a Postgres child process (a backend or an auxiliary
- * process, like bgwriter).  We can cope with concurrent signals for different
+ * process, like checkpointer).  We can cope with concurrent signals for different
  * reasons.  However, if the same reason is signaled multiple times in quick
  * succession, the process is likely to observe only one notification of it.
  * This is okay for the present uses.

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 4fe08df..f9b839c 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -315,6 +315,9 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			case BgWriterProcess:
 				statmsg = "writer process";
 				break;
+			case CheckpointerProcess:
+				statmsg = "checkpointer process";
+				break;
 			case WalWriterProcess:
 				statmsg = "wal writer process";
 				break;
@@ -415,6 +418,11 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			BackgroundWriterMain();
 			proc_exit(1);		/* should never return */
 
+		case CheckpointerProcess:
+			/* don't set signals, checkpointer has its own agenda */
+			CheckpointerMain();
+			proc_exit(1);		/* should never return */
+
 		case WalWriterProcess:
 			/* don't set signals, walwriter has its own agenda */
 			InitXLOGAccess();
diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 0767e97..e7414d2 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -13,6 +13,6 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = autovacuum.o bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o \
-	syslogger.o walwriter.o
+	syslogger.o walwriter.o checkpointer.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2d0b639..e0f3167 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -10,20 +10,13 @@
  * still empowered to issue writes if the bgwriter fails to maintain enough
  * clean shared buffers.
  *
- * The bgwriter is also charged with handling all checkpoints.	It will
- * automatically dispatch a checkpoint after a certain amount of time has
- * elapsed since the last one, and it can be signaled to perform requested
- * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
- * so many WAL segments is implemented by having backends signal the bgwriter
- * when they fill WAL segments; the bgwriter itself doesn't watch for the
- * condition.)
+ * As of Postgres 9.2 the bgwriter no longer handles checkpoints.
  *
  * The bgwriter is started by the postmaster as soon as the startup subprocess
  * finishes, or as soon as recovery begins if we are doing archive recovery.
  * It remains alive until the postmaster commands it to terminate.
- * Normal termination is by SIGUSR2, which instructs the bgwriter to execute
- * a shutdown checkpoint and then exit(0).	(All backends must be stopped
- * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
+ * Emergency termination is by SIGQUIT; like any
  * backend, the bgwriter will simply abort and exit on SIGQUIT.
  *
  * If the bgwriter exits unexpectedly, the postmaster treats that the same
@@ -54,7 +47,6 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
-#include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
@@ -67,96 +59,15 @@
 #include "utils/resowner.h"
 
 
-/*----------
- * Shared memory area for communication between bgwriter and backends
- *
- * The ckpt counters allow backends to watch for completion of a checkpoint
- * request they send.  Here's how it works:
- *	* At start of a checkpoint, bgwriter reads (and clears) the request flags
- *	  and increments ckpt_started, while holding ckpt_lck.
- *	* On completion of a checkpoint, bgwriter sets ckpt_done to
- *	  equal ckpt_started.
- *	* On failure of a checkpoint, bgwriter increments ckpt_failed
- *	  and sets ckpt_done to equal ckpt_started.
- *
- * The algorithm for backends is:
- *	1. Record current values of ckpt_failed and ckpt_started, and
- *	   set request flags, while holding ckpt_lck.
- *	2. Send signal to request checkpoint.
- *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
- *	   begun since you started this algorithm (although *not* that it was
- *	   specifically initiated by your signal), and that it is using your flags.
- *	4. Record new value of ckpt_started.
- *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
- *	   arithmetic here in case counters wrap around.)  Now you know a
- *	   checkpoint has started and completed, but not whether it was
- *	   successful.
- *	6. If ckpt_failed is different from the originally saved value,
- *	   assume request failed; otherwise it was definitely successful.
- *
- * ckpt_flags holds the OR of the checkpoint request flags sent by all
- * requesting backends since the last checkpoint start.  The flags are
- * chosen so that OR'ing is the correct way to combine multiple requests.
- *
- * num_backend_writes is used to count the number of buffer writes performed
- * by non-bgwriter processes.  This counter should be wide enough that it
- * can't overflow during a single bgwriter cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the background writer failed to absorb their request.
- *
- * The requests array holds fsync requests sent by backends and not yet
- * absorbed by the bgwriter.
- *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by BgWriterCommLock.
- *----------
- */
-typedef struct
-{
-	RelFileNodeBackend rnode;
-	ForkNumber	forknum;
-	BlockNumber segno;			/* see md.c for special values */
-	/* might add a real request-type field later; not needed yet */
-} BgWriterRequest;
-
-typedef struct
-{
-	pid_t		bgwriter_pid;	/* PID of bgwriter (0 if not started) */
-
-	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
-
-	int			ckpt_started;	/* advances when checkpoint starts */
-	int			ckpt_done;		/* advances when checkpoint done */
-	int			ckpt_failed;	/* advances when checkpoint fails */
-
-	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
-
-	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
-	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
-
-	int			num_requests;	/* current # of requests */
-	int			max_requests;	/* allocated array size */
-	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
-} BgWriterShmemStruct;
-
-static BgWriterShmemStruct *BgWriterShmem;
-
-/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
-#define WRITES_PER_ABSORB		1000
-
 /*
  * GUC parameters
  */
 int			BgWriterDelay = 200;
-int			CheckPointTimeout = 300;
-int			CheckPointWarning = 30;
-double		CheckPointCompletionTarget = 0.5;
 
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
 static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t checkpoint_requested = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -164,29 +75,14 @@ static volatile sig_atomic_t shutdown_requested = false;
  */
 static bool am_bg_writer = false;
 
-static bool ckpt_active = false;
-
-/* these values are valid when ckpt_active is true: */
-static pg_time_t ckpt_start_time;
-static XLogRecPtr ckpt_start_recptr;
-static double ckpt_cached_elapsed;
-
-static pg_time_t last_checkpoint_time;
-static pg_time_t last_xlog_switch_time;
-
 /* Prototypes for private functions */
 
-static void CheckArchiveTimeout(void);
 static void BgWriterNap(void);
-static bool IsCheckpointOnSchedule(double progress);
-static bool ImmediateCheckpointRequested(void);
-static bool CompactBgwriterRequestQueue(void);
 
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
 static void BgSigHupHandler(SIGNAL_ARGS);
-static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -202,7 +98,6 @@ BackgroundWriterMain(void)
 	sigjmp_buf	local_sigjmp_buf;
 	MemoryContext bgwriter_context;
 
-	BgWriterShmem->bgwriter_pid = MyProcPid;
 	am_bg_writer = true;
 
 	/*
@@ -228,8 +123,8 @@ BackgroundWriterMain(void)
 	 * process to participate in ProcSignal signalling.
 	 */
 	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
-	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
-	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
+	pqsignal(SIGINT, SIG_IGN);			/* as of 9.2 no longer requests checkpoint */
+	pqsignal(SIGTERM, SIG_IGN); 		/* ignore SIGTERM */
 	pqsignal(SIGQUIT, bg_quickdie);		/* hard crash time */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
@@ -249,11 +144,6 @@ BackgroundWriterMain(void)
 	sigdelset(&BlockSig, SIGQUIT);
 
 	/*
-	 * Initialize so that first time-driven event happens at the correct time.
-	 */
-	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
-
-	/*
 	 * Create a resource owner to keep track of our resources (currently only
 	 * buffer pins).
 	 */
@@ -305,20 +195,6 @@ BackgroundWriterMain(void)
 		AtEOXact_Files();
 		AtEOXact_HashTables(false);
 
-		/* Warn any waiting backends that the checkpoint failed. */
-		if (ckpt_active)
-		{
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_failed++;
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			ckpt_active = false;
-		}
-
 		/*
 		 * Now return to normal top-level context and clear ErrorContext for
 		 * next time.
@@ -361,19 +237,11 @@ BackgroundWriterMain(void)
 	if (RecoveryInProgress())
 		ThisTimeLineID = GetRecoveryTargetTLI();
 
-	/* Do this once before starting the loop, then just at SIGHUP time. */
-	SyncRepUpdateSyncStandbysDefined();
-
 	/*
 	 * Loop forever
 	 */
 	for (;;)
 	{
-		bool		do_checkpoint = false;
-		int			flags = 0;
-		pg_time_t	now;
-		int			elapsed_secs;
-
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -381,23 +249,11 @@ BackgroundWriterMain(void)
 		if (!PostmasterIsAlive())
 			exit(1);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		AbsorbFsyncRequests();
-
 		if (got_SIGHUP)
 		{
 			got_SIGHUP = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-		if (checkpoint_requested)
-		{
-			checkpoint_requested = false;
-			do_checkpoint = true;
-			BgWriterStats.m_requested_checkpoints++;
 		}
 		if (shutdown_requested)
 		{
@@ -406,142 +262,14 @@ BackgroundWriterMain(void)
 			 * control back to the sigsetjmp block above
 			 */
 			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
 			/* Normal exit from the bgwriter is here */
 			proc_exit(0);		/* done */
 		}
 
 		/*
-		 * Force a checkpoint if too much time has elapsed since the last one.
-		 * Note that we count a timed checkpoint in stats only when this
-		 * occurs without an external request, but we set the CAUSE_TIME flag
-		 * bit even if there is also an external request.
+		 * Do one cycle of dirty-buffer writing.
 		 */
-		now = (pg_time_t) time(NULL);
-		elapsed_secs = now - last_checkpoint_time;
-		if (elapsed_secs >= CheckPointTimeout)
-		{
-			if (!do_checkpoint)
-				BgWriterStats.m_timed_checkpoints++;
-			do_checkpoint = true;
-			flags |= CHECKPOINT_CAUSE_TIME;
-		}
-
-		/*
-		 * Do a checkpoint if requested, otherwise do one cycle of
-		 * dirty-buffer writing.
-		 */
-		if (do_checkpoint)
-		{
-			bool		ckpt_performed = false;
-			bool		do_restartpoint;
-
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			/*
-			 * Check if we should perform a checkpoint or a restartpoint. As a
-			 * side-effect, RecoveryInProgress() initializes TimeLineID if
-			 * it's not set yet.
-			 */
-			do_restartpoint = RecoveryInProgress();
-
-			/*
-			 * Atomically fetch the request flags to figure out what kind of a
-			 * checkpoint we should perform, and increase the started-counter
-			 * to acknowledge that we've started a new checkpoint.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			flags |= bgs->ckpt_flags;
-			bgs->ckpt_flags = 0;
-			bgs->ckpt_started++;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			/*
-			 * The end-of-recovery checkpoint is a real checkpoint that's
-			 * performed while we're still in recovery.
-			 */
-			if (flags & CHECKPOINT_END_OF_RECOVERY)
-				do_restartpoint = false;
-
-			/*
-			 * We will warn if (a) too soon since last checkpoint (whatever
-			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
-			 * since the last checkpoint start.  Note in particular that this
-			 * implementation will not generate warnings caused by
-			 * CheckPointTimeout < CheckPointWarning.
-			 */
-			if (!do_restartpoint &&
-				(flags & CHECKPOINT_CAUSE_XLOG) &&
-				elapsed_secs < CheckPointWarning)
-				ereport(LOG,
-						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
-				"checkpoints are occurring too frequently (%d seconds apart)",
-									   elapsed_secs,
-									   elapsed_secs),
-						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
-
-			/*
-			 * Initialize bgwriter-private variables used during checkpoint.
-			 */
-			ckpt_active = true;
-			if (!do_restartpoint)
-				ckpt_start_recptr = GetInsertRecPtr();
-			ckpt_start_time = now;
-			ckpt_cached_elapsed = 0;
-
-			/*
-			 * Do the checkpoint.
-			 */
-			if (!do_restartpoint)
-			{
-				CreateCheckPoint(flags);
-				ckpt_performed = true;
-			}
-			else
-				ckpt_performed = CreateRestartPoint(flags);
-
-			/*
-			 * After any checkpoint, close all smgr files.	This is so we
-			 * won't hang onto smgr references to deleted files indefinitely.
-			 */
-			smgrcloseall();
-
-			/*
-			 * Indicate checkpoint completion to any waiting backends.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (ckpt_performed)
-			{
-				/*
-				 * Note we record the checkpoint start time not end time as
-				 * last_checkpoint_time.  This is so that time-driven
-				 * checkpoints happen at a predictable spacing.
-				 */
-				last_checkpoint_time = now;
-			}
-			else
-			{
-				/*
-				 * We were not able to perform the restartpoint (checkpoints
-				 * throw an ERROR in case of error).  Most likely because we
-				 * have not received any new checkpoint WAL records since the
-				 * last restartpoint. Try again in 15 s.
-				 */
-				last_checkpoint_time = now - CheckPointTimeout + 15;
-			}
-
-			ckpt_active = false;
-		}
-		else
-			BgBufferSync();
-
-		/* Check for archive_timeout and switch xlog files if necessary. */
-		CheckArchiveTimeout();
+		BgBufferSync();
 
 		/* Nap for the configured time. */
 		BgWriterNap();
@@ -549,61 +277,6 @@ BackgroundWriterMain(void)
 }
 
 /*
- * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
- *
- * This will switch to a new WAL file and force an archive file write
- * if any activity is recorded in the current WAL file, including just
- * a single checkpoint record.
- */
-static void
-CheckArchiveTimeout(void)
-{
-	pg_time_t	now;
-	pg_time_t	last_time;
-
-	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
-		return;
-
-	now = (pg_time_t) time(NULL);
-
-	/* First we do a quick check using possibly-stale local state. */
-	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
-		return;
-
-	/*
-	 * Update local state ... note that last_xlog_switch_time is the last time
-	 * a switch was performed *or requested*.
-	 */
-	last_time = GetLastSegSwitchTime();
-
-	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
-
-	/* Now we can do the real check */
-	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
-	{
-		XLogRecPtr	switchpoint;
-
-		/* OK, it's time to switch */
-		switchpoint = RequestXLogSwitch();
-
-		/*
-		 * If the returned pointer points exactly to a segment boundary,
-		 * assume nothing happened.
-		 */
-		if ((switchpoint.xrecoff % XLogSegSize) != 0)
-			ereport(DEBUG1,
-				(errmsg("transaction log switch forced (archive_timeout=%d)",
-						XLogArchiveTimeout)));
-
-		/*
-		 * Update state in any case, so we don't retry constantly when the
-		 * system is idle.
-		 */
-		last_xlog_switch_time = now;
-	}
-}
-
-/*
  * BgWriterNap -- Nap for the configured time or until a signal is received.
  */
 static void
@@ -624,185 +297,24 @@ BgWriterNap(void)
 	 * respond reasonably promptly when someone signals us, break down the
 	 * sleep into 1-second increments, and check for interrupts after each
 	 * nap.
-	 *
-	 * We absorb pending requests after each short sleep.
 	 */
-	if (bgwriter_lru_maxpages > 0 || ckpt_active)
+	if (bgwriter_lru_maxpages > 0)
 		udelay = BgWriterDelay * 1000L;
-	else if (XLogArchiveTimeout > 0)
-		udelay = 1000000L;		/* One second */
 	else
 		udelay = 10000000L;		/* Ten seconds */
 
 	while (udelay > 999999L)
 	{
-		if (got_SIGHUP || shutdown_requested ||
-		(ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested))
+		if (got_SIGHUP || shutdown_requested)
 			break;
 		pg_usleep(1000000L);
-		AbsorbFsyncRequests();
 		udelay -= 1000000L;
 	}
 
-	if (!(got_SIGHUP || shutdown_requested ||
-	  (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested)))
+	if (!(got_SIGHUP || shutdown_requested))
 		pg_usleep(udelay);
 }
 
-/*
- * Returns true if an immediate checkpoint request is pending.	(Note that
- * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
- * there is one pending behind it.)
- */
-static bool
-ImmediateCheckpointRequested(void)
-{
-	if (checkpoint_requested)
-	{
-		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-		/*
-		 * We don't need to acquire the ckpt_lck in this case because we're
-		 * only looking at a single flag bit.
-		 */
-		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
-			return true;
-	}
-	return false;
-}
-
-/*
- * CheckpointWriteDelay -- yield control to bgwriter during a checkpoint
- *
- * This function is called after each page write performed by BufferSync().
- * It is responsible for keeping the bgwriter's normal activities in
- * progress during a long checkpoint, and for throttling BufferSync()'s
- * write rate to hit checkpoint_completion_target.
- *
- * The checkpoint request flags should be passed in; currently the only one
- * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
- *
- * 'progress' is an estimate of how much of the work has been done, as a
- * fraction between 0.0 meaning none, and 1.0 meaning all done.
- */
-void
-CheckpointWriteDelay(int flags, double progress)
-{
-	static int	absorb_counter = WRITES_PER_ABSORB;
-
-	/* Do nothing if checkpoint is being executed by non-bgwriter process */
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * Perform the usual bgwriter duties and take a nap, unless we're behind
-	 * schedule, in which case we just try to catch up as quickly as possible.
-	 */
-	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
-		!ImmediateCheckpointRequested() &&
-		IsCheckpointOnSchedule(progress))
-	{
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-
-		BgBufferSync();
-		CheckArchiveTimeout();
-		BgWriterNap();
-	}
-	else if (--absorb_counter <= 0)
-	{
-		/*
-		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
-		 * operations even when we don't sleep, to prevent overflow of the
-		 * fsync request queue.
-		 */
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-	}
-}
-
-/*
- * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
- *		 in time?
- *
- * Compares the current progress against the time/segments elapsed since last
- * checkpoint, and returns true if the progress we've made this far is greater
- * than the elapsed time/segments.
- */
-static bool
-IsCheckpointOnSchedule(double progress)
-{
-	XLogRecPtr	recptr;
-	struct timeval now;
-	double		elapsed_xlogs,
-				elapsed_time;
-
-	Assert(ckpt_active);
-
-	/* Scale progress according to checkpoint_completion_target. */
-	progress *= CheckPointCompletionTarget;
-
-	/*
-	 * Check against the cached value first. Only do the more expensive
-	 * calculations once we reach the target previously calculated. Since
-	 * neither time or WAL insert pointer moves backwards, a freshly
-	 * calculated value can only be greater than or equal to the cached value.
-	 */
-	if (progress < ckpt_cached_elapsed)
-		return false;
-
-	/*
-	 * Check progress against WAL segments written and checkpoint_segments.
-	 *
-	 * We compare the current WAL insert location against the location
-	 * computed before calling CreateCheckPoint. The code in XLogInsert that
-	 * actually triggers a checkpoint when checkpoint_segments is exceeded
-	 * compares against RedoRecptr, so this is not completely accurate.
-	 * However, it's good enough for our purposes, we're only calculating an
-	 * estimate anyway.
-	 */
-	if (!RecoveryInProgress())
-	{
-		recptr = GetInsertRecPtr();
-		elapsed_xlogs =
-			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
-			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
-			CheckPointSegments;
-
-		if (progress < elapsed_xlogs)
-		{
-			ckpt_cached_elapsed = elapsed_xlogs;
-			return false;
-		}
-	}
-
-	/*
-	 * Check progress against time elapsed and checkpoint_timeout.
-	 */
-	gettimeofday(&now, NULL);
-	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
-					now.tv_usec / 1000000.0) / CheckPointTimeout;
-
-	if (progress < elapsed_time)
-	{
-		ckpt_cached_elapsed = elapsed_time;
-		return false;
-	}
-
-	/* It looks like we're on schedule. */
-	return true;
-}
-
-
 /* --------------------------------
  *		signal handler routines
  * --------------------------------
@@ -847,441 +359,9 @@ BgSigHupHandler(SIGNAL_ARGS)
 	got_SIGHUP = true;
 }
 
-/* SIGINT: set flag to run a normal checkpoint right away */
-static void
-ReqCheckpointHandler(SIGNAL_ARGS)
-{
-	checkpoint_requested = true;
-}
-
 /* SIGUSR2: set flag to run a shutdown checkpoint and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
 }
-
-
-/* --------------------------------
- *		communication with backends
- * --------------------------------
- */
-
-/*
- * BgWriterShmemSize
- *		Compute space needed for bgwriter-related shared memory
- */
-Size
-BgWriterShmemSize(void)
-{
-	Size		size;
-
-	/*
-	 * Currently, the size of the requests[] array is arbitrarily set equal to
-	 * NBuffers.  This may prove too large or small ...
-	 */
-	size = offsetof(BgWriterShmemStruct, requests);
-	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
-
-	return size;
-}
-
-/*
- * BgWriterShmemInit
- *		Allocate and initialize bgwriter-related shared memory
- */
-void
-BgWriterShmemInit(void)
-{
-	bool		found;
-
-	BgWriterShmem = (BgWriterShmemStruct *)
-		ShmemInitStruct("Background Writer Data",
-						BgWriterShmemSize(),
-						&found);
-
-	if (!found)
-	{
-		/* First time through, so initialize */
-		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
-		SpinLockInit(&BgWriterShmem->ckpt_lck);
-		BgWriterShmem->max_requests = NBuffers;
-	}
-}
-
-/*
- * RequestCheckpoint
- *		Called in backend processes to request a checkpoint
- *
- * flags is a bitwise OR of the following:
- *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
- *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
- *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
- *		ignoring checkpoint_completion_target parameter.
- *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
- *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
- *		CHECKPOINT_END_OF_RECOVERY).
- *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
- *		just signal bgwriter to do it, and return).
- *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
- *		(This affects logging, and in particular enables CheckPointWarning.)
- */
-void
-RequestCheckpoint(int flags)
-{
-	/* use volatile pointer to prevent code rearrangement */
-	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-	int			ntries;
-	int			old_failed,
-				old_started;
-
-	/*
-	 * If in a standalone backend, just do it ourselves.
-	 */
-	if (!IsPostmasterEnvironment)
-	{
-		/*
-		 * There's no point in doing slow checkpoints in a standalone backend,
-		 * because there's no other backends the checkpoint could disrupt.
-		 */
-		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
-
-		/*
-		 * After any checkpoint, close all smgr files.	This is so we won't
-		 * hang onto smgr references to deleted files indefinitely.
-		 */
-		smgrcloseall();
-
-		return;
-	}
-
-	/*
-	 * Atomically set the request flags, and take a snapshot of the counters.
-	 * When we see ckpt_started > old_started, we know the flags we set here
-	 * have been seen by bgwriter.
-	 *
-	 * Note that we OR the flags with any existing flags, to avoid overriding
-	 * a "stronger" request by another backend.  The flag senses must be
-	 * chosen to make this work!
-	 */
-	SpinLockAcquire(&bgs->ckpt_lck);
-
-	old_failed = bgs->ckpt_failed;
-	old_started = bgs->ckpt_started;
-	bgs->ckpt_flags |= flags;
-
-	SpinLockRelease(&bgs->ckpt_lck);
-
-	/*
-	 * Send signal to request checkpoint.  It's possible that the bgwriter
-	 * hasn't started yet, or is in process of restarting, so we will retry a
-	 * few times if needed.  Also, if not told to wait for the checkpoint to
-	 * occur, we consider failure to send the signal to be nonfatal and merely
-	 * LOG it.
-	 */
-	for (ntries = 0;; ntries++)
-	{
-		if (BgWriterShmem->bgwriter_pid == 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-				"could not request checkpoint because bgwriter not running");
-				break;
-			}
-		}
-		else if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-					 "could not signal for checkpoint: %m");
-				break;
-			}
-		}
-		else
-			break;				/* signal sent successfully */
-
-		CHECK_FOR_INTERRUPTS();
-		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
-	}
-
-	/*
-	 * If requested, wait for completion.  We detect completion according to
-	 * the algorithm given above.
-	 */
-	if (flags & CHECKPOINT_WAIT)
-	{
-		int			new_started,
-					new_failed;
-
-		/* Wait for a new checkpoint to start. */
-		for (;;)
-		{
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_started = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_started != old_started)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		/*
-		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
-		 */
-		for (;;)
-		{
-			int			new_done;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_done = bgs->ckpt_done;
-			new_failed = bgs->ckpt_failed;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_done - new_started >= 0)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		if (new_failed != old_failed)
-			ereport(ERROR,
-					(errmsg("checkpoint request failed"),
-					 errhint("Consult recent messages in the server log for details.")));
-	}
-}
-
-/*
- * ForwardFsyncRequest
- *		Forward a file-fsync request from a backend to the bgwriter
- *
- * Whenever a backend is compelled to write directly to a relation
- * (which should be seldom, if the bgwriter is getting its job done),
- * the backend calls this routine to pass over knowledge that the relation
- * is dirty and must be fsync'd before next checkpoint.  We also use this
- * opportunity to count such writes for statistical purposes.
- *
- * segno specifies which segment (not block!) of the relation needs to be
- * fsync'd.  (Since the valid range is much less than BlockNumber, we can
- * use high values for special flags; that's all internal to md.c, which
- * see for details.)
- *
- * To avoid holding the lock for longer than necessary, we normally write
- * to the requests[] queue without checking for duplicates.  The bgwriter
- * will have to eliminate dups internally anyway.  However, if we discover
- * that the queue is full, we make a pass over the entire queue to compact
- * it.	This is somewhat expensive, but the alternative is for the backend
- * to perform its own fsync, which is far more expensive in practice.  It
- * is theoretically possible a backend fsync might still be necessary, if
- * the queue is full and contains no duplicate entries.  In that case, we
- * let the backend know by returning false.
- */
-bool
-ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
-					BlockNumber segno)
-{
-	BgWriterRequest *request;
-
-	if (!IsUnderPostmaster)
-		return false;			/* probably shouldn't even get here */
-
-	if (am_bg_writer)
-		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
-
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Count all backend writes regardless of if they fit in the queue */
-	BgWriterShmem->num_backend_writes++;
-
-	/*
-	 * If the background writer isn't running or the request queue is full,
-	 * the backend will have to perform its own fsync request.	But before
-	 * forcing that to happen, we can try to compact the background writer
-	 * request queue.
-	 */
-	if (BgWriterShmem->bgwriter_pid == 0 ||
-		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
-		 && !CompactBgwriterRequestQueue()))
-	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		BgWriterShmem->num_backend_fsync++;
-		LWLockRelease(BgWriterCommLock);
-		return false;
-	}
-	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
-	request->rnode = rnode;
-	request->forknum = forknum;
-	request->segno = segno;
-	LWLockRelease(BgWriterCommLock);
-	return true;
-}
-
-/*
- * CompactBgwriterRequestQueue
- *		Remove duplicates from the request queue to avoid backend fsyncs.
- *
- * Although a full fsync request queue is not common, it can lead to severe
- * performance problems when it does happen.  So far, this situation has
- * only been observed to occur when the system is under heavy write load,
- * and especially during the "sync" phase of a checkpoint.	Without this
- * logic, each backend begins doing an fsync for every block written, which
- * gets very expensive and can slow down the whole system.
- *
- * Trying to do this every time the queue is full could lose if there
- * aren't any removable entries.  But should be vanishingly rare in
- * practice: there's one queue entry per shared buffer.
- */
-static bool
-CompactBgwriterRequestQueue()
-{
-	struct BgWriterSlotMapping
-	{
-		BgWriterRequest request;
-		int			slot;
-	};
-
-	int			n,
-				preserve_count;
-	int			num_skipped = 0;
-	HASHCTL		ctl;
-	HTAB	   *htab;
-	bool	   *skip_slot;
-
-	/* must hold BgWriterCommLock in exclusive mode */
-	Assert(LWLockHeldByMe(BgWriterCommLock));
-
-	/* Initialize temporary hash table */
-	MemSet(&ctl, 0, sizeof(ctl));
-	ctl.keysize = sizeof(BgWriterRequest);
-	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
-	ctl.hash = tag_hash;
-	htab = hash_create("CompactBgwriterRequestQueue",
-					   BgWriterShmem->num_requests,
-					   &ctl,
-					   HASH_ELEM | HASH_FUNCTION);
-
-	/* Initialize skip_slot array */
-	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
-
-	/*
-	 * The basic idea here is that a request can be skipped if it's followed
-	 * by a later, identical request.  It might seem more sensible to work
-	 * backwards from the end of the queue and check whether a request is
-	 * *preceded* by an earlier, identical request, in the hopes of doing less
-	 * copying.  But that might change the semantics, if there's an
-	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
-	 * we do it this way.  It would be possible to be even smarter if we made
-	 * the code below understand the specific semantics of such requests (it
-	 * could blow away preceding entries that would end up being canceled
-	 * anyhow), but it's not clear that the extra complexity would buy us
-	 * anything.
-	 */
-	for (n = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		BgWriterRequest *request;
-		struct BgWriterSlotMapping *slotmap;
-		bool		found;
-
-		request = &BgWriterShmem->requests[n];
-		slotmap = hash_search(htab, request, HASH_ENTER, &found);
-		if (found)
-		{
-			skip_slot[slotmap->slot] = true;
-			++num_skipped;
-		}
-		slotmap->slot = n;
-	}
-
-	/* Done with the hash table. */
-	hash_destroy(htab);
-
-	/* If no duplicates, we're out of luck. */
-	if (!num_skipped)
-	{
-		pfree(skip_slot);
-		return false;
-	}
-
-	/* We found some duplicates; remove them. */
-	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		if (skip_slot[n])
-			continue;
-		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
-	}
-	ereport(DEBUG1,
-	   (errmsg("compacted fsync request queue from %d entries to %d entries",
-			   BgWriterShmem->num_requests, preserve_count)));
-	BgWriterShmem->num_requests = preserve_count;
-
-	/* Cleanup. */
-	pfree(skip_slot);
-	return true;
-}
-
-/*
- * AbsorbFsyncRequests
- *		Retrieve queued fsync requests and pass them to local smgr.
- *
- * This is exported because it must be called during CreateCheckPoint;
- * we have to be sure we have accepted all pending requests just before
- * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
- * non-bgwriter processes, do nothing if not bgwriter.
- */
-void
-AbsorbFsyncRequests(void)
-{
-	BgWriterRequest *requests = NULL;
-	BgWriterRequest *request;
-	int			n;
-
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * We have to PANIC if we fail to absorb all the pending requests (eg,
-	 * because our hashtable runs out of memory).  This is because the system
-	 * cannot run safely if we are unable to fsync what we have been told to
-	 * fsync.  Fortunately, the hashtable is so small that the problem is
-	 * quite unlikely to arise in practice.
-	 */
-	START_CRIT_SECTION();
-
-	/*
-	 * We try to avoid holding the lock for a long time by copying the request
-	 * array.
-	 */
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Transfer write count into pending pgstats message */
-	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
-	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
-
-	BgWriterShmem->num_backend_writes = 0;
-	BgWriterShmem->num_backend_fsync = 0;
-
-	n = BgWriterShmem->num_requests;
-	if (n > 0)
-	{
-		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
-		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
-	}
-	BgWriterShmem->num_requests = 0;
-
-	LWLockRelease(BgWriterCommLock);
-
-	for (request = requests; n > 0; request++, n--)
-		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
-
-	if (requests)
-		pfree(requests);
-
-	END_CRIT_SECTION();
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
new file mode 100644
index 0000000..f9e2e4f
--- /dev/null
+++ b/src/backend/postmaster/checkpointer.c
@@ -0,0 +1,1236 @@
+/*-------------------------------------------------------------------------
+ *
+ * checkpointer.c
+ *
+ * The checkpointer is new as of Postgres 9.2.  It handles all checkpoints.
+ * Checkpoints are automatically dispatched after a certain amount of time has
+ * elapsed since the last one, and it can be signaled to perform requested
+ * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
+ * so many WAL segments is implemented by having backends signal when they
+ * fill WAL segments; the checkpointer itself doesn't watch for the
+ * condition.)
+ *
+ * The checkpointer is started by the postmaster as soon as the startup subprocess
+ * finishes, or as soon as recovery begins if we are doing archive recovery.
+ * It remains alive until the postmaster commands it to terminate.
+ * Normal termination is by SIGUSR2, which instructs the checkpointer to execute
+ * a shutdown checkpoint and then exit(0).	(All backends must be stopped
+ * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * backend, the checkpointer will simply abort and exit on SIGQUIT.
+ *
+ * If the checkpointer exits unexpectedly, the postmaster treats that the same
+ * as a backend crash: shared memory may be corrupted, so remaining backends
+ * should be killed by SIGQUIT and then a recovery cycle started.  (Even if
+ * shared memory isn't corrupted, we have lost information about which
+ * files need to be fsync'd for the next checkpoint, and so a system
+ * restart needs to be forced.)
+ *
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/checkpointer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <signal.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "access/xlog_internal.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgwriter.h"
+#include "replication/syncrep.h"
+#include "storage/bufmgr.h"
+#include "storage/ipc.h"
+#include "storage/lwlock.h"
+#include "storage/pmsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+
+/*----------
+ * Shared memory area for communication between checkpointer and backends
+ *
+ * The ckpt counters allow backends to watch for completion of a checkpoint
+ * request they send.  Here's how it works:
+ *	* At start of a checkpoint, checkpointer reads (and clears) the request flags
+ *	  and increments ckpt_started, while holding ckpt_lck.
+ *	* On completion of a checkpoint, checkpointer sets ckpt_done to
+ *	  equal ckpt_started.
+ *	* On failure of a checkpoint, checkpointer increments ckpt_failed
+ *	  and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ *	1. Record current values of ckpt_failed and ckpt_started, and
+ *	   set request flags, while holding ckpt_lck.
+ *	2. Send signal to request checkpoint.
+ *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
+ *	   begun since you started this algorithm (although *not* that it was
+ *	   specifically initiated by your signal), and that it is using your flags.
+ *	4. Record new value of ckpt_started.
+ *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
+ *	   arithmetic here in case counters wrap around.)  Now you know a
+ *	   checkpoint has started and completed, but not whether it was
+ *	   successful.
+ *	6. If ckpt_failed is different from the originally saved value,
+ *	   assume request failed; otherwise it was definitely successful.
+ *
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start.  The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by non-bgwriter processes.  This counter should be wide enough that it
+ * can't overflow during a single bgwriter cycle.  num_backend_fsync
+ * counts the subset of those writes that also had to do their own fsync,
+ * because the background writer failed to absorb their request.
+ *
+ * The requests array holds fsync requests sent by backends and not yet
+ * absorbed by the checkpointer.
+ *
+ * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
+ * the requests fields are protected by BgWriterCommLock.
+ *----------
+ */
+typedef struct
+{
+	RelFileNodeBackend rnode;
+	ForkNumber	forknum;
+	BlockNumber segno;			/* see md.c for special values */
+	/* might add a real request-type field later; not needed yet */
+} BgWriterRequest;
+
+typedef struct
+{
+	pid_t		checkpointer_pid;	/* PID of bgwriter (0 if not started) */
+
+	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
+
+	int			ckpt_started;	/* advances when checkpoint starts */
+	int			ckpt_done;		/* advances when checkpoint done */
+	int			ckpt_failed;	/* advances when checkpoint fails */
+
+	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
+
+	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
+	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
+
+	int			num_requests;	/* current # of requests */
+	int			max_requests;	/* allocated array size */
+	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
+} BgWriterShmemStruct;
+
+static BgWriterShmemStruct *BgWriterShmem;
+
+/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB		1000
+
+/*
+ * GUC parameters
+ */
+int			CheckPointTimeout = 300;
+int			CheckPointWarning = 30;
+double		CheckPointCompletionTarget = 0.5;
+
+/*
+ * Flags set by interrupt handlers for later service in the main loop.
+ */
+static volatile sig_atomic_t got_SIGHUP = false;
+static volatile sig_atomic_t checkpoint_requested = false;
+static volatile sig_atomic_t shutdown_requested = false;
+
+/*
+ * Private state
+ */
+static bool am_checkpointer = false;
+
+static bool ckpt_active = false;
+
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void CheckArchiveTimeout(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+static bool CompactCheckpointerRequestQueue(void);
+
+/* Signal handlers */
+
+static void chkpt_quickdie(SIGNAL_ARGS);
+static void ChkptSigHupHandler(SIGNAL_ARGS);
+static void ReqCheckpointHandler(SIGNAL_ARGS);
+static void ReqShutdownHandler(SIGNAL_ARGS);
+
+
+/*
+ * Main entry point for checkpointer process
+ *
+ * This is invoked from BootstrapMain, which has already created the basic
+ * execution environment, but not enabled signals yet.
+ */
+void
+CheckpointerMain(void)
+{
+	sigjmp_buf	local_sigjmp_buf;
+	MemoryContext checkpointer_context;
+
+	BgWriterShmem->checkpointer_pid = MyProcPid;
+	am_checkpointer = true;
+
+	/*
+	 * If possible, make this process a group leader, so that the postmaster
+	 * can signal any child processes too.	(checkpointer probably never has any
+	 * child processes, but for consistency we make all postmaster child
+	 * processes do this.)
+	 */
+#ifdef HAVE_SETSID
+	if (setsid() < 0)
+		elog(FATAL, "setsid() failed: %m");
+#endif
+
+	/*
+	 * Properly accept or ignore signals the postmaster might send us
+	 *
+	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
+	 * system shutdown cycle, init will SIGTERM all processes at once.	We
+	 * want to wait for the backends to exit, whereupon the postmaster will
+	 * tell us it's okay to shut down (via SIGUSR2).
+	 *
+	 * SIGUSR1 is presently unused; keep it spare in case someday we want this
+	 * process to participate in ProcSignal signalling.
+	 */
+	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGINT, ReqCheckpointHandler);	/* request checkpoint */
+	pqsignal(SIGTERM, SIG_IGN);				/* ignore SIGTERM */
+	pqsignal(SIGQUIT, chkpt_quickdie);		/* hard crash time */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
+	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */
+
+	/*
+	 * Reset some signals that are accepted by postmaster but not here
+	 */
+	pqsignal(SIGCHLD, SIG_DFL);
+	pqsignal(SIGTTIN, SIG_DFL);
+	pqsignal(SIGTTOU, SIG_DFL);
+	pqsignal(SIGCONT, SIG_DFL);
+	pqsignal(SIGWINCH, SIG_DFL);
+
+	/* We allow SIGQUIT (quickdie) at all times */
+	sigdelset(&BlockSig, SIGQUIT);
+
+	/*
+	 * Initialize so that first time-driven event happens at the correct time.
+	 */
+	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
+
+	/*
+	 * Create a resource owner to keep track of our resources (currently only
+	 * buffer pins).
+	 */
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer");
+
+	/*
+	 * Create a memory context that we will do all our work in.  We do this so
+	 * that we can reset the context during error recovery and thereby avoid
+	 * possible memory leaks.  Formerly this code just ran in
+	 * TopMemoryContext, but resetting that would be a really bad idea.
+	 */
+	checkpointer_context = AllocSetContextCreate(TopMemoryContext,
+											 "Checkpointer",
+											 ALLOCSET_DEFAULT_MINSIZE,
+											 ALLOCSET_DEFAULT_INITSIZE,
+											 ALLOCSET_DEFAULT_MAXSIZE);
+	MemoryContextSwitchTo(checkpointer_context);
+
+	/*
+	 * If an exception is encountered, processing resumes here.
+	 *
+	 * See notes in postgres.c about the design of this coding.
+	 */
+	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
+	{
+		/* Since not using PG_TRY, must reset error stack by hand */
+		error_context_stack = NULL;
+
+		/* Prevent interrupts while cleaning up */
+		HOLD_INTERRUPTS();
+
+		/* Report the error to the server log */
+		EmitErrorReport();
+
+		/*
+		 * These operations are really just a minimal subset of
+		 * AbortTransaction().	We don't have very many resources to worry
+		 * about in checkpointer, but we do have LWLocks, buffers, and temp files.
+		 */
+		LWLockReleaseAll();
+		AbortBufferIO();
+		UnlockBuffers();
+		/* buffer pins are released here: */
+		ResourceOwnerRelease(CurrentResourceOwner,
+							 RESOURCE_RELEASE_BEFORE_LOCKS,
+							 false, true);
+		/* we needn't bother with the other ResourceOwnerRelease phases */
+		AtEOXact_Buffers(false);
+		AtEOXact_Files();
+		AtEOXact_HashTables(false);
+
+		/* Warn any waiting backends that the checkpoint failed. */
+		if (ckpt_active)
+		{
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_failed++;
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Now return to normal top-level context and clear ErrorContext for
+		 * next time.
+		 */
+		MemoryContextSwitchTo(checkpointer_context);
+		FlushErrorState();
+
+		/* Flush any leaked data in the top-level context */
+		MemoryContextResetAndDeleteChildren(checkpointer_context);
+
+		/* Now we can allow interrupts again */
+		RESUME_INTERRUPTS();
+
+		/*
+		 * Sleep at least 1 second after any error.  A write error is likely
+		 * to be repeated, and we don't want to be filling the error logs as
+		 * fast as we can.
+		 */
+		pg_usleep(1000000L);
+
+		/*
+		 * Close all open files after any error.  This is helpful on Windows,
+		 * where holding deleted files open causes various strange errors.
+		 * It's not clear we need it elsewhere, but shouldn't hurt.
+		 */
+		smgrcloseall();
+	}
+
+	/* We can now handle ereport(ERROR) */
+	PG_exception_stack = &local_sigjmp_buf;
+
+	/*
+	 * Unblock signals (they were blocked when the postmaster forked us)
+	 */
+	PG_SETMASK(&UnBlockSig);
+
+	/*
+	 * Use the recovery target timeline ID during recovery
+	 */
+	if (RecoveryInProgress())
+		ThisTimeLineID = GetRecoveryTargetTLI();
+
+	/* Do this once before starting the loop, then just at SIGHUP time. */
+	SyncRepUpdateSyncStandbysDefined();
+
+	/*
+	 * Loop forever
+	 */
+	for (;;)
+	{
+		bool		do_checkpoint = false;
+		int			flags = 0;
+		pg_time_t	now;
+		int			elapsed_secs;
+
+		/*
+		 * Emergency bailout if postmaster has died.  This is to avoid the
+		 * necessity for manual cleanup of all postmaster children.
+		 */
+		if (!PostmasterIsAlive())
+			exit(1);
+
+		/*
+		 * Process any requests or signals received recently.
+		 */
+		AbsorbFsyncRequests();
+
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+		if (checkpoint_requested)
+		{
+			checkpoint_requested = false;
+			do_checkpoint = true;
+			BgWriterStats.m_requested_checkpoints++;
+		}
+		if (shutdown_requested)
+		{
+			/*
+			 * From here on, elog(ERROR) should end with exit(1), not send
+			 * control back to the sigsetjmp block above
+			 */
+			ExitOnAnyError = true;
+			/* Close down the database */
+			ShutdownXLOG(0, 0);
+			/* Normal exit from the checkpointer is here */
+			proc_exit(0);		/* done */
+		}
+
+		/*
+		 * Force a checkpoint if too much time has elapsed since the last one.
+		 * Note that we count a timed checkpoint in stats only when this
+		 * occurs without an external request, but we set the CAUSE_TIME flag
+		 * bit even if there is also an external request.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+		{
+			if (!do_checkpoint)
+				BgWriterStats.m_timed_checkpoints++;
+			do_checkpoint = true;
+			flags |= CHECKPOINT_CAUSE_TIME;
+		}
+
+		/*
+		 * Do a checkpoint if requested.
+		 */
+		if (do_checkpoint)
+		{
+			bool		ckpt_performed = false;
+			bool		do_restartpoint;
+
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			/*
+			 * Check if we should perform a checkpoint or a restartpoint. As a
+			 * side-effect, RecoveryInProgress() initializes TimeLineID if
+			 * it's not set yet.
+			 */
+			do_restartpoint = RecoveryInProgress();
+
+			/*
+			 * Atomically fetch the request flags to figure out what kind of a
+			 * checkpoint we should perform, and increase the started-counter
+			 * to acknowledge that we've started a new checkpoint.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			flags |= bgs->ckpt_flags;
+			bgs->ckpt_flags = 0;
+			bgs->ckpt_started++;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			/*
+			 * The end-of-recovery checkpoint is a real checkpoint that's
+			 * performed while we're still in recovery.
+			 */
+			if (flags & CHECKPOINT_END_OF_RECOVERY)
+				do_restartpoint = false;
+
+			/*
+			 * We will warn if (a) too soon since last checkpoint (whatever
+			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+			 * since the last checkpoint start.  Note in particular that this
+			 * implementation will not generate warnings caused by
+			 * CheckPointTimeout < CheckPointWarning.
+			 */
+			if (!do_restartpoint &&
+				(flags & CHECKPOINT_CAUSE_XLOG) &&
+				elapsed_secs < CheckPointWarning)
+				ereport(LOG,
+						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+				"checkpoints are occurring too frequently (%d seconds apart)",
+									   elapsed_secs,
+									   elapsed_secs),
+						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
+
+			/*
+			 * Initialize checkpointer-private variables used during checkpoint.
+			 */
+			ckpt_active = true;
+			if (!do_restartpoint)
+				ckpt_start_recptr = GetInsertRecPtr();
+			ckpt_start_time = now;
+			ckpt_cached_elapsed = 0;
+
+			/*
+			 * Do the checkpoint.
+			 */
+			if (!do_restartpoint)
+			{
+				CreateCheckPoint(flags);
+				ckpt_performed = true;
+			}
+			else
+				ckpt_performed = CreateRestartPoint(flags);
+
+			/*
+			 * After any checkpoint, close all smgr files.	This is so we
+			 * won't hang onto smgr references to deleted files indefinitely.
+			 */
+			smgrcloseall();
+
+			/*
+			 * Indicate checkpoint completion to any waiting backends.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (ckpt_performed)
+			{
+				/*
+				 * Note we record the checkpoint start time not end time as
+				 * last_checkpoint_time.  This is so that time-driven
+				 * checkpoints happen at a predictable spacing.
+				 */
+				last_checkpoint_time = now;
+			}
+			else
+			{
+				/*
+				 * We were not able to perform the restartpoint (checkpoints
+				 * throw an ERROR in case of error).  Most likely because we
+				 * have not received any new checkpoint WAL records since the
+				 * last restartpoint. Try again in 15 s.
+				 */
+				last_checkpoint_time = now - CheckPointTimeout + 15;
+			}
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Nap for a while and then loop again. Later patches will replace
+		 * this with a latch loop. Keep it simple now for clarity.
+		 * Relatively long sleep because the bgwriter does cleanup now.
+		 */
+		pg_usleep(500000L);
+
+		/* Check for archive_timeout and switch xlog files if necessary. */
+		CheckArchiveTimeout();
+	}
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ *
+ * This will switch to a new WAL file and force an archive file write
+ * if any activity is recorded in the current WAL file, including just
+ * a single checkpoint record.
+ */
+static void
+CheckArchiveTimeout(void)
+{
+	pg_time_t	now;
+	pg_time_t	last_time;
+
+	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+		return;
+
+	now = (pg_time_t) time(NULL);
+
+	/* First we do a quick check using possibly-stale local state. */
+	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+		return;
+
+	/*
+	 * Update local state ... note that last_xlog_switch_time is the last time
+	 * a switch was performed *or requested*.
+	 */
+	last_time = GetLastSegSwitchTime();
+
+	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+	/* Now we can do the real check */
+	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+	{
+		XLogRecPtr	switchpoint;
+
+		/* OK, it's time to switch */
+		switchpoint = RequestXLogSwitch();
+
+		/*
+		 * If the returned pointer points exactly to a segment boundary,
+		 * assume nothing happened.
+		 */
+		if ((switchpoint.xrecoff % XLogSegSize) != 0)
+			ereport(DEBUG1,
+				(errmsg("transaction log switch forced (archive_timeout=%d)",
+						XLogArchiveTimeout)));
+
+		/*
+		 * Update state in any case, so we don't retry constantly when the
+		 * system is idle.
+		 */
+		last_xlog_switch_time = now;
+	}
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending.	(Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+	if (checkpoint_requested)
+	{
+		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+		/*
+		 * We don't need to acquire the ckpt_lck in this case because we're
+		 * only looking at a single flag bit.
+		 */
+		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * CheckpointWriteDelay -- control rate of checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for throttling BufferSync()'s write rate to hit
+ * checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+	static int	absorb_counter = WRITES_PER_ABSORB;
+
+	/* Do nothing if checkpoint is being executed by non-checkpointer process */
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * Perform the usual duties and take a nap, unless we're behind
+	 * schedule, in which case we just try to catch up as quickly as possible.
+	 */
+	if (!(flags & CHECKPOINT_IMMEDIATE) &&
+		!shutdown_requested &&
+		!ImmediateCheckpointRequested() &&
+		IsCheckpointOnSchedule(progress))
+	{
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+
+		CheckArchiveTimeout();
+
+		/*
+		 * Checkpoint sleep used to be connected to bgwriter_delay at 200ms.
+		 * That resulted in more frequent wakeups if not much work to do.
+		 * Checkpointer and bgwriter are no longer related so take the Big Sleep.
+		 */
+		pg_usleep(500000L);
+	}
+	else if (--absorb_counter <= 0)
+	{
+		/*
+		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+		 * operations even when we don't sleep, to prevent overflow of the
+		 * fsync request queue.
+		 */
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+	}
+}
+
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ *		 in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+	XLogRecPtr	recptr;
+	struct timeval now;
+	double		elapsed_xlogs,
+				elapsed_time;
+
+	Assert(ckpt_active);
+
+	/* Scale progress according to checkpoint_completion_target. */
+	progress *= CheckPointCompletionTarget;
+
+	/*
+	 * Check against the cached value first. Only do the more expensive
+	 * calculations once we reach the target previously calculated. Since
+	 * neither time or WAL insert pointer moves backwards, a freshly
+	 * calculated value can only be greater than or equal to the cached value.
+	 */
+	if (progress < ckpt_cached_elapsed)
+		return false;
+
+	/*
+	 * Check progress against WAL segments written and checkpoint_segments.
+	 *
+	 * We compare the current WAL insert location against the location
+	 * computed before calling CreateCheckPoint. The code in XLogInsert that
+	 * actually triggers a checkpoint when checkpoint_segments is exceeded
+	 * compares against RedoRecptr, so this is not completely accurate.
+	 * However, it's good enough for our purposes, we're only calculating an
+	 * estimate anyway.
+	 */
+	if (!RecoveryInProgress())
+	{
+		recptr = GetInsertRecPtr();
+		elapsed_xlogs =
+			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
+			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
+			CheckPointSegments;
+
+		if (progress < elapsed_xlogs)
+		{
+			ckpt_cached_elapsed = elapsed_xlogs;
+			return false;
+		}
+	}
+
+	/*
+	 * Check progress against time elapsed and checkpoint_timeout.
+	 */
+	gettimeofday(&now, NULL);
+	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+					now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+	if (progress < elapsed_time)
+	{
+		ckpt_cached_elapsed = elapsed_time;
+		return false;
+	}
+
+	/* It looks like we're on schedule. */
+	return true;
+}
+
+
+/* --------------------------------
+ *		signal handler routines
+ * --------------------------------
+ */
+
+/*
+ * chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
+ *
+ * Some backend has bought the farm,
+ * so we need to stop what we're doing and exit.
+ */
+static void
+chkpt_quickdie(SIGNAL_ARGS)
+{
+	PG_SETMASK(&BlockSig);
+
+	/*
+	 * We DO NOT want to run proc_exit() callbacks -- we're here because
+	 * shared memory may be corrupted, so we don't want to try to clean up our
+	 * transaction.  Just nail the windows shut and get out of town.  Now that
+	 * there's an atexit callback to prevent third-party code from breaking
+	 * things by calling exit() directly, we have to reset the callbacks
+	 * explicitly to make this work as intended.
+	 */
+	on_exit_reset();
+
+	/*
+	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
+	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
+	 * backend.  This is necessary precisely because we don't clean up our
+	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
+	 * should ensure the postmaster sees this as a crash, too, but no harm in
+	 * being doubly sure.)
+	 */
+	exit(2);
+}
+
+/* SIGHUP: set flag to re-read config file at next convenient time */
+static void
+ChkptSigHupHandler(SIGNAL_ARGS)
+{
+	got_SIGHUP = true;
+}
+
+/* SIGINT: set flag to run a normal checkpoint right away */
+static void
+ReqCheckpointHandler(SIGNAL_ARGS)
+{
+	checkpoint_requested = true;
+}
+
+/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
+static void
+ReqShutdownHandler(SIGNAL_ARGS)
+{
+	shutdown_requested = true;
+}
+
+
+/* --------------------------------
+ *		communication with backends
+ * --------------------------------
+ */
+
+/*
+ * BgWriterShmemSize
+ *		Compute space needed for bgwriter-related shared memory
+ */
+Size
+BgWriterShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Currently, the size of the requests[] array is arbitrarily set equal to
+	 * NBuffers.  This may prove too large or small ...
+	 */
+	size = offsetof(BgWriterShmemStruct, requests);
+	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
+
+	return size;
+}
+
+/*
+ * BgWriterShmemInit
+ *		Allocate and initialize bgwriter-related shared memory
+ */
+void
+BgWriterShmemInit(void)
+{
+	bool		found;
+
+	BgWriterShmem = (BgWriterShmemStruct *)
+		ShmemInitStruct("Background Writer Data",
+						BgWriterShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
+		SpinLockInit(&BgWriterShmem->ckpt_lck);
+		BgWriterShmem->max_requests = NBuffers;
+	}
+}
+
+/*
+ * RequestCheckpoint
+ *		Called in backend processes to request a checkpoint
+ *
+ * flags is a bitwise OR of the following:
+ *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ *		ignoring checkpoint_completion_target parameter.
+ *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
+ *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ *		CHECKPOINT_END_OF_RECOVERY).
+ *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ *		just signal bgwriter to do it, and return).
+ *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ *		(This affects logging, and in particular enables CheckPointWarning.)
+ */
+void
+RequestCheckpoint(int flags)
+{
+	/* use volatile pointer to prevent code rearrangement */
+	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+	int			ntries;
+	int			old_failed,
+				old_started;
+
+	/*
+	 * If in a standalone backend, just do it ourselves.
+	 */
+	if (!IsPostmasterEnvironment)
+	{
+		/*
+		 * There's no point in doing slow checkpoints in a standalone backend,
+		 * because there's no other backends the checkpoint could disrupt.
+		 */
+		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
+
+		/*
+		 * After any checkpoint, close all smgr files.	This is so we won't
+		 * hang onto smgr references to deleted files indefinitely.
+		 */
+		smgrcloseall();
+
+		return;
+	}
+
+	/*
+	 * Atomically set the request flags, and take a snapshot of the counters.
+	 * When we see ckpt_started > old_started, we know the flags we set here
+	 * have been seen by bgwriter.
+	 *
+	 * Note that we OR the flags with any existing flags, to avoid overriding
+	 * a "stronger" request by another backend.  The flag senses must be
+	 * chosen to make this work!
+	 */
+	SpinLockAcquire(&bgs->ckpt_lck);
+
+	old_failed = bgs->ckpt_failed;
+	old_started = bgs->ckpt_started;
+	bgs->ckpt_flags |= flags;
+
+	SpinLockRelease(&bgs->ckpt_lck);
+
+	/*
+	 * Send signal to request checkpoint.  It's possible that the bgwriter
+	 * hasn't started yet, or is in process of restarting, so we will retry a
+	 * few times if needed.  Also, if not told to wait for the checkpoint to
+	 * occur, we consider failure to send the signal to be nonfatal and merely
+	 * LOG it.
+	 */
+	for (ntries = 0;; ntries++)
+	{
+		if (BgWriterShmem->checkpointer_pid == 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+				"could not request checkpoint because bgwriter not running");
+				break;
+			}
+		}
+		else if (kill(BgWriterShmem->checkpointer_pid, SIGINT) != 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: %m");
+				break;
+			}
+		}
+		else
+			break;				/* signal sent successfully */
+
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
+	}
+
+	/*
+	 * If requested, wait for completion.  We detect completion according to
+	 * the algorithm given above.
+	 */
+	if (flags & CHECKPOINT_WAIT)
+	{
+		int			new_started,
+					new_failed;
+
+		/* Wait for a new checkpoint to start. */
+		for (;;)
+		{
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_started = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_started != old_started)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		/*
+		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
+		 */
+		for (;;)
+		{
+			int			new_done;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_done = bgs->ckpt_done;
+			new_failed = bgs->ckpt_failed;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_done - new_started >= 0)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		if (new_failed != old_failed)
+			ereport(ERROR,
+					(errmsg("checkpoint request failed"),
+					 errhint("Consult recent messages in the server log for details.")));
+	}
+}
+
+/*
+ * ForwardFsyncRequest
+ *		Forward a file-fsync request from a backend to the bgwriter
+ *
+ * Whenever a backend is compelled to write directly to a relation
+ * (which should be seldom, if the bgwriter is getting its job done),
+ * the backend calls this routine to pass over knowledge that the relation
+ * is dirty and must be fsync'd before next checkpoint.  We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * segno specifies which segment (not block!) of the relation needs to be
+ * fsync'd.  (Since the valid range is much less than BlockNumber, we can
+ * use high values for special flags; that's all internal to md.c, which
+ * see for details.)
+ *
+ * To avoid holding the lock for longer than necessary, we normally write
+ * to the requests[] queue without checking for duplicates.  The bgwriter
+ * will have to eliminate dups internally anyway.  However, if we discover
+ * that the queue is full, we make a pass over the entire queue to compact
+ * it.	This is somewhat expensive, but the alternative is for the backend
+ * to perform its own fsync, which is far more expensive in practice.  It
+ * is theoretically possible a backend fsync might still be necessary, if
+ * the queue is full and contains no duplicate entries.  In that case, we
+ * let the backend know by returning false.
+ */
+bool
+ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
+					BlockNumber segno)
+{
+	BgWriterRequest *request;
+
+	if (!IsUnderPostmaster)
+		return false;			/* probably shouldn't even get here */
+
+	if (am_checkpointer)
+		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
+
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Count all backend writes regardless of if they fit in the queue */
+	BgWriterShmem->num_backend_writes++;
+
+	/*
+	 * If the background writer isn't running or the request queue is full,
+	 * the backend will have to perform its own fsync request.	But before
+	 * forcing that to happen, we can try to compact the background writer
+	 * request queue.
+	 */
+	if (BgWriterShmem->checkpointer_pid == 0 ||
+		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
+		 && !CompactCheckpointerRequestQueue()))
+	{
+		/*
+		 * Count the subset of writes where backends have to do their own
+		 * fsync
+		 */
+		BgWriterShmem->num_backend_fsync++;
+		LWLockRelease(BgWriterCommLock);
+		return false;
+	}
+	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
+	request->rnode = rnode;
+	request->forknum = forknum;
+	request->segno = segno;
+	LWLockRelease(BgWriterCommLock);
+	return true;
+}
+
+/*
+ * CompactCheckpointerRequestQueue
+ *		Remove duplicates from the request queue to avoid backend fsyncs.
+ *
+ * Although a full fsync request queue is not common, it can lead to severe
+ * performance problems when it does happen.  So far, this situation has
+ * only been observed to occur when the system is under heavy write load,
+ * and especially during the "sync" phase of a checkpoint.	Without this
+ * logic, each backend begins doing an fsync for every block written, which
+ * gets very expensive and can slow down the whole system.
+ *
+ * Trying to do this every time the queue is full could lose if there
+ * aren't any removable entries.  But should be vanishingly rare in
+ * practice: there's one queue entry per shared buffer.
+ */
+static bool
+CompactCheckpointerRequestQueue()
+{
+	struct BgWriterSlotMapping
+	{
+		BgWriterRequest request;
+		int			slot;
+	};
+
+	int			n,
+				preserve_count;
+	int			num_skipped = 0;
+	HASHCTL		ctl;
+	HTAB	   *htab;
+	bool	   *skip_slot;
+
+	/* must hold BgWriterCommLock in exclusive mode */
+	Assert(LWLockHeldByMe(BgWriterCommLock));
+
+	/* Initialize temporary hash table */
+	MemSet(&ctl, 0, sizeof(ctl));
+	ctl.keysize = sizeof(BgWriterRequest);
+	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
+	ctl.hash = tag_hash;
+	htab = hash_create("CompactBgwriterRequestQueue",
+					   BgWriterShmem->num_requests,
+					   &ctl,
+					   HASH_ELEM | HASH_FUNCTION);
+
+	/* Initialize skip_slot array */
+	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
+
+	/*
+	 * The basic idea here is that a request can be skipped if it's followed
+	 * by a later, identical request.  It might seem more sensible to work
+	 * backwards from the end of the queue and check whether a request is
+	 * *preceded* by an earlier, identical request, in the hopes of doing less
+	 * copying.  But that might change the semantics, if there's an
+	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
+	 * we do it this way.  It would be possible to be even smarter if we made
+	 * the code below understand the specific semantics of such requests (it
+	 * could blow away preceding entries that would end up being canceled
+	 * anyhow), but it's not clear that the extra complexity would buy us
+	 * anything.
+	 */
+	for (n = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		BgWriterRequest *request;
+		struct BgWriterSlotMapping *slotmap;
+		bool		found;
+
+		request = &BgWriterShmem->requests[n];
+		slotmap = hash_search(htab, request, HASH_ENTER, &found);
+		if (found)
+		{
+			skip_slot[slotmap->slot] = true;
+			++num_skipped;
+		}
+		slotmap->slot = n;
+	}
+
+	/* Done with the hash table. */
+	hash_destroy(htab);
+
+	/* If no duplicates, we're out of luck. */
+	if (!num_skipped)
+	{
+		pfree(skip_slot);
+		return false;
+	}
+
+	/* We found some duplicates; remove them. */
+	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		if (skip_slot[n])
+			continue;
+		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
+	}
+	ereport(DEBUG1,
+	   (errmsg("compacted fsync request queue from %d entries to %d entries",
+			   BgWriterShmem->num_requests, preserve_count)));
+	BgWriterShmem->num_requests = preserve_count;
+
+	/* Cleanup. */
+	pfree(skip_slot);
+	return true;
+}
+
+/*
+ * AbsorbFsyncRequests
+ *		Retrieve queued fsync requests and pass them to local smgr.
+ *
+ * This is exported because it must be called during CreateCheckPoint;
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
+ * non-checkpointer processes, do nothing if not checkpointer.
+ */
+void
+AbsorbFsyncRequests(void)
+{
+	BgWriterRequest *requests = NULL;
+	BgWriterRequest *request;
+	int			n;
+
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * We have to PANIC if we fail to absorb all the pending requests (eg,
+	 * because our hashtable runs out of memory).  This is because the system
+	 * cannot run safely if we are unable to fsync what we have been told to
+	 * fsync.  Fortunately, the hashtable is so small that the problem is
+	 * quite unlikely to arise in practice.
+	 */
+	START_CRIT_SECTION();
+
+	/*
+	 * We try to avoid holding the lock for a long time by copying the request
+	 * array.
+	 */
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Transfer write count into pending pgstats message */
+	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
+	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
+
+	BgWriterShmem->num_backend_writes = 0;
+	BgWriterShmem->num_backend_fsync = 0;
+
+	n = BgWriterShmem->num_requests;
+	if (n > 0)
+	{
+		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
+		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
+	}
+	BgWriterShmem->num_requests = 0;
+
+	LWLockRelease(BgWriterCommLock);
+
+	for (request = requests; n > 0; request++, n--)
+		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
+
+	if (requests)
+		pfree(requests);
+
+	END_CRIT_SECTION();
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 0a84d97..c8599c2 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -206,6 +206,7 @@ bool		restart_after_crash = true;
 /* PIDs of special child processes; 0 when not running */
 static pid_t StartupPID = 0,
 			BgWriterPID = 0,
+			CheckpointerPID = 0,
 			WalWriterPID = 0,
 			WalReceiverPID = 0,
 			AutoVacPID = 0,
@@ -277,7 +278,7 @@ typedef enum
 	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
 	PM_WAIT_READONLY,			/* waiting for read only backends to exit */
 	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
-	PM_SHUTDOWN,				/* waiting for bgwriter to do shutdown ckpt */
+	PM_SHUTDOWN,				/* waiting for checkpointer to do shutdown ckpt */
 	PM_SHUTDOWN_2,				/* waiting for archiver and walsenders to
 								 * finish */
 	PM_WAIT_DEAD_END,			/* waiting for dead_end children to exit */
@@ -463,6 +464,7 @@ static void ShmemBackendArrayRemove(Backend *bn);
 
 #define StartupDataBase()		StartChildProcess(StartupProcess)
 #define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
+#define StartCheckpointer()		StartChildProcess(CheckpointerProcess)
 #define StartWalWriter()		StartChildProcess(WalWriterProcess)
 #define StartWalReceiver()		StartChildProcess(WalReceiverProcess)
 
@@ -1015,8 +1017,8 @@ PostmasterMain(int argc, char *argv[])
 	 * CAUTION: when changing this list, check for side-effects on the signal
 	 * handling setup of child processes.  See tcop/postgres.c,
 	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
-	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c, and
-	 * postmaster/syslogger.c.
+	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
+	 * postmaster/syslogger.c and postmaster/checkpointer.c
 	 */
 	pqinitmask();
 	PG_SETMASK(&BlockSig);
@@ -1353,10 +1355,14 @@ ServerLoop(void)
 		 * state that prevents it, start one.  It doesn't matter if this
 		 * fails, we'll just try again later.
 		 */
-		if (BgWriterPID == 0 &&
-			(pmState == PM_RUN || pmState == PM_RECOVERY ||
-			 pmState == PM_HOT_STANDBY))
-			BgWriterPID = StartBackgroundWriter();
+		if (pmState == PM_RUN || pmState == PM_RECOVERY ||
+			 pmState == PM_HOT_STANDBY)
+		{
+			if (BgWriterPID == 0)
+				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
+		}
 
 		/*
 		 * Likewise, if we have lost the walwriter process, try to start a new
@@ -2034,6 +2040,8 @@ SIGHUP_handler(SIGNAL_ARGS)
 			signal_child(StartupPID, SIGHUP);
 		if (BgWriterPID != 0)
 			signal_child(BgWriterPID, SIGHUP);
+		if (CheckpointerPID != 0)
+			signal_child(CheckpointerPID, SIGHUP);
 		if (WalWriterPID != 0)
 			signal_child(WalWriterPID, SIGHUP);
 		if (WalReceiverPID != 0)
@@ -2148,7 +2156,7 @@ pmdie(SIGNAL_ARGS)
 				signal_child(WalReceiverPID, SIGTERM);
 			if (pmState == PM_RECOVERY)
 			{
-				/* only bgwriter is active in this state */
+				/* only checkpointer is active in this state */
 				pmState = PM_WAIT_BACKENDS;
 			}
 			else if (pmState == PM_RUN ||
@@ -2193,6 +2201,8 @@ pmdie(SIGNAL_ARGS)
 				signal_child(StartupPID, SIGQUIT);
 			if (BgWriterPID != 0)
 				signal_child(BgWriterPID, SIGQUIT);
+			if (CheckpointerPID != 0)
+				signal_child(CheckpointerPID, SIGQUIT);
 			if (WalWriterPID != 0)
 				signal_child(WalWriterPID, SIGQUIT);
 			if (WalReceiverPID != 0)
@@ -2323,12 +2333,14 @@ reaper(SIGNAL_ARGS)
 			}
 
 			/*
-			 * Crank up the background writer, if we didn't do that already
+			 * Crank up background tasks, if we didn't do that already
 			 * when we entered consistent recovery state.  It doesn't matter
 			 * if this fails, we'll just try again later.
 			 */
 			if (BgWriterPID == 0)
 				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
 
 			/*
 			 * Likewise, start other special children as needed.  In a restart
@@ -2356,10 +2368,22 @@ reaper(SIGNAL_ARGS)
 		if (pid == BgWriterPID)
 		{
 			BgWriterPID = 0;
+			if (!EXIT_STATUS_0(exitstatus))
+				HandleChildCrash(pid, exitstatus,
+								 _("background writer process"));
+			continue;
+		}
+
+		/*
+		 * Was it the checkpointer?
+		 */
+		if (pid == CheckpointerPID)
+		{
+			CheckpointerPID = 0;
 			if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
 			{
 				/*
-				 * OK, we saw normal exit of the bgwriter after it's been told
+				 * OK, we saw normal exit of the checkpointer after it's been told
 				 * to shut down.  We expect that it wrote a shutdown
 				 * checkpoint.	(If for some reason it didn't, recovery will
 				 * occur on next postmaster start.)
@@ -2396,11 +2420,11 @@ reaper(SIGNAL_ARGS)
 			else
 			{
 				/*
-				 * Any unexpected exit of the bgwriter (including FATAL exit)
+				 * Any unexpected exit of the checkpointer (including FATAL exit)
 				 * is treated as a crash.
 				 */
 				HandleChildCrash(pid, exitstatus,
-								 _("background writer process"));
+								 _("checkpointer process"));
 			}
 
 			continue;
@@ -2584,8 +2608,8 @@ CleanupBackend(int pid,
 }
 
 /*
- * HandleChildCrash -- cleanup after failed backend, bgwriter, walwriter,
- * or autovacuum.
+ * HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
+ * walwriter or autovacuum.
  *
  * The objectives here are to clean up our local state about the child
  * process, and to signal all other remaining children to quickdie.
@@ -2678,6 +2702,18 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 		signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
 	}
 
+	/* Take care of the checkpointer too */
+	if (pid == CheckpointerPID)
+		CheckpointerPID = 0;
+	else if (CheckpointerPID != 0 && !FatalError)
+	{
+		ereport(DEBUG2,
+				(errmsg_internal("sending %s to process %d",
+								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
+								 (int) CheckpointerPID)));
+		signal_child(CheckpointerPID, (SendStop ? SIGSTOP : SIGQUIT));
+	}
+
 	/* Take care of the walwriter too */
 	if (pid == WalWriterPID)
 		WalWriterPID = 0;
@@ -2857,9 +2893,10 @@ PostmasterStateMachine(void)
 	{
 		/*
 		 * PM_WAIT_BACKENDS state ends when we have no regular backends
-		 * (including autovac workers) and no walwriter or autovac launcher.
-		 * If we are doing crash recovery then we expect the bgwriter to exit
-		 * too, otherwise not.	The archiver, stats, and syslogger processes
+		 * (including autovac workers) and no walwriter, autovac launcher
+		 * or bgwriter.  If we are doing crash recovery then we expect the
+		 * checkpointer to exit as well, otherwise not.
+		 * The archiver, stats, and syslogger processes
 		 * are disregarded since they are not connected to shared memory; we
 		 * also disregard dead_end children here. Walsenders are also
 		 * disregarded, they will be terminated later after writing the
@@ -2868,7 +2905,8 @@ PostmasterStateMachine(void)
 		if (CountChildren(BACKEND_TYPE_NORMAL | BACKEND_TYPE_AUTOVAC) == 0 &&
 			StartupPID == 0 &&
 			WalReceiverPID == 0 &&
-			(BgWriterPID == 0 || !FatalError) &&
+			BgWriterPID == 0 &&
+			(CheckpointerPID == 0 || !FatalError) &&
 			WalWriterPID == 0 &&
 			AutoVacPID == 0)
 		{
@@ -2890,22 +2928,22 @@ PostmasterStateMachine(void)
 				/*
 				 * If we get here, we are proceeding with normal shutdown. All
 				 * the regular children are gone, and it's time to tell the
-				 * bgwriter to do a shutdown checkpoint.
+				 * checkpointer to do a shutdown checkpoint.
 				 */
 				Assert(Shutdown > NoShutdown);
-				/* Start the bgwriter if not running */
-				if (BgWriterPID == 0)
-					BgWriterPID = StartBackgroundWriter();
+				/* Start the checkpointer if not running */
+				if (CheckpointerPID == 0)
+					CheckpointerPID = StartCheckpointer();
 				/* And tell it to shut down */
-				if (BgWriterPID != 0)
+				if (CheckpointerPID != 0)
 				{
-					signal_child(BgWriterPID, SIGUSR2);
+					signal_child(CheckpointerPID, SIGUSR2);
 					pmState = PM_SHUTDOWN;
 				}
 				else
 				{
 					/*
-					 * If we failed to fork a bgwriter, just shut down. Any
+					 * If we failed to fork a checkpointer, just shut down. Any
 					 * required cleanup will happen at next restart. We set
 					 * FatalError so that an "abnormal shutdown" message gets
 					 * logged when we exit.
@@ -2964,6 +3002,7 @@ PostmasterStateMachine(void)
 			Assert(StartupPID == 0);
 			Assert(WalReceiverPID == 0);
 			Assert(BgWriterPID == 0);
+			Assert(CheckpointerPID == 0);
 			Assert(WalWriterPID == 0);
 			Assert(AutoVacPID == 0);
 			/* syslogger is not considered here */
@@ -4143,6 +4182,8 @@ sigusr1_handler(SIGNAL_ARGS)
 		 */
 		Assert(BgWriterPID == 0);
 		BgWriterPID = StartBackgroundWriter();
+		Assert(CheckpointerPID == 0);
+		CheckpointerPID = StartCheckpointer();
 
 		pmState = PM_RECOVERY;
 	}
@@ -4429,6 +4470,10 @@ StartChildProcess(AuxProcType type)
 				ereport(LOG,
 				   (errmsg("could not fork background writer process: %m")));
 				break;
+			case CheckpointerProcess:
+				ereport(LOG,
+				   (errmsg("could not fork checkpointer process: %m")));
+				break;
 			case WalWriterProcess:
 				ereport(LOG,
 						(errmsg("could not fork WAL writer process: %m")));
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8647edd..184e820 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1278,11 +1278,9 @@ BufferSync(int flags)
 					break;
 
 				/*
-				 * Perform normal bgwriter duties and sleep to throttle our
-				 * I/O rate.
+				 * Sleep to throttle our I/O rate.
 				 */
-				CheckpointWriteDelay(flags,
-									 (double) num_written / num_to_write);
+				CheckpointWriteDelay(flags, (double) num_written / num_to_write);
 			}
 		}
 
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 3015885..a761369 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -38,7 +38,7 @@
 /*
  * Special values for the segno arg to RememberFsyncRequest.
  *
- * Note that CompactBgwriterRequestQueue assumes that it's OK to remove an
+ * Note that CompactcheckpointerRequestQueue assumes that it's OK to remove an
  * fsync request from the queue if an identical, subsequent request is found.
  * See comments there before making changes here.
  */
@@ -77,7 +77,7 @@
  *	Inactive segments are those that once contained data but are currently
  *	not needed because of an mdtruncate() operation.  The reason for leaving
  *	them present at size zero, rather than unlinking them, is that other
- *	backends and/or the bgwriter might be holding open file references to
+ *	backends and/or the checkpointer might be holding open file references to
  *	such segments.	If the relation expands again after mdtruncate(), such
  *	that a deactivated segment becomes active again, it is important that
  *	such file references still be valid --- else data might get written
@@ -111,7 +111,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
 
 
 /*
- * In some contexts (currently, standalone backends and the bgwriter process)
+ * In some contexts (currently, standalone backends and the checkpointer process)
  * we keep track of pending fsync operations: we need to remember all relation
  * segments that have been written since the last checkpoint, so that we can
  * fsync them down to disk before completing the next checkpoint.  This hash
@@ -123,7 +123,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
  * a hash table, because we don't expect there to be any duplicate requests.
  *
  * (Regular backends do not track pending operations locally, but forward
- * them to the bgwriter.)
+ * them to the checkpointer.)
  */
 typedef struct
 {
@@ -194,7 +194,7 @@ mdinit(void)
 	 * Create pending-operations hashtable if we need it.  Currently, we need
 	 * it if we are standalone (not under a postmaster) OR if we are a
 	 * bootstrap-mode subprocess of a postmaster (that is, a startup or
-	 * bgwriter process).
+	 * checkpointer process).
 	 */
 	if (!IsUnderPostmaster || IsBootstrapProcessingMode())
 	{
@@ -214,10 +214,10 @@ mdinit(void)
 }
 
 /*
- * In archive recovery, we rely on bgwriter to do fsyncs, but we will have
+ * In archive recovery, we rely on checkpointer to do fsyncs, but we will have
  * already created the pendingOpsTable during initialization of the startup
  * process.  Calling this function drops the local pendingOpsTable so that
- * subsequent requests will be forwarded to bgwriter.
+ * subsequent requests will be forwarded to checkpointer.
  */
 void
 SetForwardFsyncRequests(void)
@@ -765,9 +765,9 @@ mdnblocks(SMgrRelation reln, ForkNumber forknum)
 	 * NOTE: this assumption could only be wrong if another backend has
 	 * truncated the relation.	We rely on higher code levels to handle that
 	 * scenario by closing and re-opening the md fd, which is handled via
-	 * relcache flush.	(Since the bgwriter doesn't participate in relcache
+	 * relcache flush.	(Since the checkpointer doesn't participate in relcache
 	 * flush, it could have segment chain entries for inactive segments;
-	 * that's OK because the bgwriter never needs to compute relation size.)
+	 * that's OK because the checkpointer never needs to compute relation size.)
 	 */
 	while (v->mdfd_chain != NULL)
 	{
@@ -957,7 +957,7 @@ mdsync(void)
 		elog(ERROR, "cannot sync without a pendingOpsTable");
 
 	/*
-	 * If we are in the bgwriter, the sync had better include all fsync
+	 * If we are in the checkpointer, the sync had better include all fsync
 	 * requests that were queued by backends up to this point.	The tightest
 	 * race condition that could occur is that a buffer that must be written
 	 * and fsync'd for the checkpoint could have been dumped by a backend just
@@ -1033,7 +1033,7 @@ mdsync(void)
 			int			failures;
 
 			/*
-			 * If in bgwriter, we want to absorb pending requests every so
+			 * If in checkpointer, we want to absorb pending requests every so
 			 * often to prevent overflow of the fsync request queue.  It is
 			 * unspecified whether newly-added entries will be visited by
 			 * hash_seq_search, but we don't care since we don't need to
@@ -1070,9 +1070,9 @@ mdsync(void)
 				 * say "but an unreferenced SMgrRelation is still a leak!" Not
 				 * really, because the only case in which a checkpoint is done
 				 * by a process that isn't about to shut down is in the
-				 * bgwriter, and it will periodically do smgrcloseall(). This
+				 * checkpointer, and it will periodically do smgrcloseall(). This
 				 * fact justifies our not closing the reln in the success path
-				 * either, which is a good thing since in non-bgwriter cases
+				 * either, which is a good thing since in non-checkpointer cases
 				 * we couldn't safely do that.)  Furthermore, in many cases
 				 * the relation will have been dirtied through this same smgr
 				 * relation, and so we can save a file open/close cycle.
@@ -1301,7 +1301,7 @@ register_unlink(RelFileNodeBackend rnode)
 	else
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the request
+		 * Notify the checkpointer about it.  If we fail to queue the request
 		 * message, we have to sleep and try again, because we can't simply
 		 * delete the file now.  Ugly, but hopefully won't happen often.
 		 *
@@ -1315,10 +1315,10 @@ register_unlink(RelFileNodeBackend rnode)
 }
 
 /*
- * RememberFsyncRequest() -- callback from bgwriter side of fsync request
+ * RememberFsyncRequest() -- callback from checkpointer side of fsync request
  *
  * We stuff most fsync requests into the local hash table for execution
- * during the bgwriter's next checkpoint.  UNLINK requests go into a
+ * during the checkpointer's next checkpoint.  UNLINK requests go into a
  * separate linked list, however, because they get processed separately.
  *
  * The range of possible segment numbers is way less than the range of
@@ -1460,20 +1460,20 @@ ForgetRelationFsyncRequests(RelFileNodeBackend rnode, ForkNumber forknum)
 	else if (IsUnderPostmaster)
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the revoke
+		 * Notify the checkpointer about it.  If we fail to queue the revoke
 		 * message, we have to sleep and try again ... ugly, but hopefully
 		 * won't happen often.
 		 *
 		 * XXX should we CHECK_FOR_INTERRUPTS in this loop?  Escaping with an
 		 * error would leave the no-longer-used file still present on disk,
-		 * which would be bad, so I'm inclined to assume that the bgwriter
+		 * which would be bad, so I'm inclined to assume that the checkpointer
 		 * will always empty the queue soon.
 		 */
 		while (!ForwardFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC))
 			pg_usleep(10000L);	/* 10 msec seems a good number */
 
 		/*
-		 * Note we don't wait for the bgwriter to actually absorb the revoke
+		 * Note we don't wait for the checkpointer to actually absorb the revoke
 		 * message; see mdsync() for the implications.
 		 */
 	}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 4eaa243..cb43879 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -256,7 +256,7 @@ typedef struct RmgrData
 extern const RmgrData RmgrTable[];
 
 /*
- * Exported to support xlog switching from bgwriter
+ * Exported to support xlog switching from checkpointer
  */
 extern pg_time_t GetLastSegSwitchTime(void);
 extern XLogRecPtr RequestXLogSwitch(void);
diff --git a/src/include/bootstrap/bootstrap.h b/src/include/bootstrap/bootstrap.h
index cee9bd1..6153b7a 100644
--- a/src/include/bootstrap/bootstrap.h
+++ b/src/include/bootstrap/bootstrap.h
@@ -22,6 +22,7 @@ typedef enum
 	BootstrapProcess,
 	StartupProcess,
 	BgWriterProcess,
+	CheckpointerProcess,
 	WalWriterProcess,
 	WalReceiverProcess,
 
diff --git a/src/include/postmaster/bgwriter.h b/src/include/postmaster/bgwriter.h
index eaf2206..c05901e 100644
--- a/src/include/postmaster/bgwriter.h
+++ b/src/include/postmaster/bgwriter.h
@@ -23,6 +23,7 @@ extern int	CheckPointWarning;
 extern double CheckPointCompletionTarget;
 
 extern void BackgroundWriterMain(void);
+extern void CheckpointerMain(void);
 
 extern void RequestCheckpoint(int flags);
 extern void CheckpointWriteDelay(int flags, double progress);
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 46ec625..6e798b1 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -190,11 +190,11 @@ extern PROC_HDR *ProcGlobal;
  * We set aside some extra PGPROC structures for auxiliary processes,
  * ie things that aren't full-fledged backends but need shmem access.
  *
- * Background writer and WAL writer run during normal operation. Startup
- * process and WAL receiver also consume 2 slots, but WAL writer is
- * launched only after startup has exited, so we only need 3 slots.
+ * Background writer, checkpointer and WAL writer run during normal operation.
+ * Startup process and WAL receiver also consume 2 slots, but WAL writer is
+ * launched only after startup has exited, so we only need 4 slots.
  */
-#define NUM_AUXILIARY_PROCS		3
+#define NUM_AUXILIARY_PROCS		4
 
 
 /* configurable options */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 2a27e0b..d5afe01 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -19,7 +19,7 @@
 
 /*
  * Reasons for signalling a Postgres child process (a backend or an auxiliary
- * process, like bgwriter).  We can cope with concurrent signals for different
+ * process, like checkpointer).  We can cope with concurrent signals for different
  * reasons.  However, if the same reason is signaled multiple times in quick
  * succession, the process is likely to observe only one notification of it.
  * This is okay for the present uses.

diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 4fe08df..f9b839c 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -315,6 +315,9 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			case BgWriterProcess:
 				statmsg = "writer process";
 				break;
+			case CheckpointerProcess:
+				statmsg = "checkpointer process";
+				break;
 			case WalWriterProcess:
 				statmsg = "wal writer process";
 				break;
@@ -415,6 +418,11 @@ AuxiliaryProcessMain(int argc, char *argv[])
 			BackgroundWriterMain();
 			proc_exit(1);		/* should never return */
 
+		case CheckpointerProcess:
+			/* don't set signals, checkpointer has its own agenda */
+			CheckpointerMain();
+			proc_exit(1);		/* should never return */
+
 		case WalWriterProcess:
 			/* don't set signals, walwriter has its own agenda */
 			InitXLOGAccess();
diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index 0767e97..e7414d2 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -13,6 +13,6 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = autovacuum.o bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o \
-	syslogger.o walwriter.o
+	syslogger.o walwriter.o checkpointer.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 2d0b639..2841cdf 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -10,20 +10,13 @@
  * still empowered to issue writes if the bgwriter fails to maintain enough
  * clean shared buffers.
  *
- * The bgwriter is also charged with handling all checkpoints.	It will
- * automatically dispatch a checkpoint after a certain amount of time has
- * elapsed since the last one, and it can be signaled to perform requested
- * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
- * so many WAL segments is implemented by having backends signal the bgwriter
- * when they fill WAL segments; the bgwriter itself doesn't watch for the
- * condition.)
+ * As of Postgres 9.2 the bgwriter no longer handles checkpoints.
  *
  * The bgwriter is started by the postmaster as soon as the startup subprocess
  * finishes, or as soon as recovery begins if we are doing archive recovery.
  * It remains alive until the postmaster commands it to terminate.
- * Normal termination is by SIGUSR2, which instructs the bgwriter to execute
- * a shutdown checkpoint and then exit(0).	(All backends must be stopped
- * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * Normal termination is by SIGUSR2, which instructs the bgwriter to exit(0).
+ * Emergency termination is by SIGQUIT; like any
  * backend, the bgwriter will simply abort and exit on SIGQUIT.
  *
  * If the bgwriter exits unexpectedly, the postmaster treats that the same
@@ -54,7 +47,6 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "postmaster/bgwriter.h"
-#include "replication/syncrep.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
@@ -67,96 +59,15 @@
 #include "utils/resowner.h"
 
 
-/*----------
- * Shared memory area for communication between bgwriter and backends
- *
- * The ckpt counters allow backends to watch for completion of a checkpoint
- * request they send.  Here's how it works:
- *	* At start of a checkpoint, bgwriter reads (and clears) the request flags
- *	  and increments ckpt_started, while holding ckpt_lck.
- *	* On completion of a checkpoint, bgwriter sets ckpt_done to
- *	  equal ckpt_started.
- *	* On failure of a checkpoint, bgwriter increments ckpt_failed
- *	  and sets ckpt_done to equal ckpt_started.
- *
- * The algorithm for backends is:
- *	1. Record current values of ckpt_failed and ckpt_started, and
- *	   set request flags, while holding ckpt_lck.
- *	2. Send signal to request checkpoint.
- *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
- *	   begun since you started this algorithm (although *not* that it was
- *	   specifically initiated by your signal), and that it is using your flags.
- *	4. Record new value of ckpt_started.
- *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
- *	   arithmetic here in case counters wrap around.)  Now you know a
- *	   checkpoint has started and completed, but not whether it was
- *	   successful.
- *	6. If ckpt_failed is different from the originally saved value,
- *	   assume request failed; otherwise it was definitely successful.
- *
- * ckpt_flags holds the OR of the checkpoint request flags sent by all
- * requesting backends since the last checkpoint start.  The flags are
- * chosen so that OR'ing is the correct way to combine multiple requests.
- *
- * num_backend_writes is used to count the number of buffer writes performed
- * by non-bgwriter processes.  This counter should be wide enough that it
- * can't overflow during a single bgwriter cycle.  num_backend_fsync
- * counts the subset of those writes that also had to do their own fsync,
- * because the background writer failed to absorb their request.
- *
- * The requests array holds fsync requests sent by backends and not yet
- * absorbed by the bgwriter.
- *
- * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
- * the requests fields are protected by BgWriterCommLock.
- *----------
- */
-typedef struct
-{
-	RelFileNodeBackend rnode;
-	ForkNumber	forknum;
-	BlockNumber segno;			/* see md.c for special values */
-	/* might add a real request-type field later; not needed yet */
-} BgWriterRequest;
-
-typedef struct
-{
-	pid_t		bgwriter_pid;	/* PID of bgwriter (0 if not started) */
-
-	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
-
-	int			ckpt_started;	/* advances when checkpoint starts */
-	int			ckpt_done;		/* advances when checkpoint done */
-	int			ckpt_failed;	/* advances when checkpoint fails */
-
-	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
-
-	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
-	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
-
-	int			num_requests;	/* current # of requests */
-	int			max_requests;	/* allocated array size */
-	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
-} BgWriterShmemStruct;
-
-static BgWriterShmemStruct *BgWriterShmem;
-
-/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
-#define WRITES_PER_ABSORB		1000
-
 /*
  * GUC parameters
  */
 int			BgWriterDelay = 200;
-int			CheckPointTimeout = 300;
-int			CheckPointWarning = 30;
-double		CheckPointCompletionTarget = 0.5;
 
 /*
  * Flags set by interrupt handlers for later service in the main loop.
  */
 static volatile sig_atomic_t got_SIGHUP = false;
-static volatile sig_atomic_t checkpoint_requested = false;
 static volatile sig_atomic_t shutdown_requested = false;
 
 /*
@@ -164,29 +75,14 @@ static volatile sig_atomic_t shutdown_requested = false;
  */
 static bool am_bg_writer = false;
 
-static bool ckpt_active = false;
-
-/* these values are valid when ckpt_active is true: */
-static pg_time_t ckpt_start_time;
-static XLogRecPtr ckpt_start_recptr;
-static double ckpt_cached_elapsed;
-
-static pg_time_t last_checkpoint_time;
-static pg_time_t last_xlog_switch_time;
-
 /* Prototypes for private functions */
 
-static void CheckArchiveTimeout(void);
 static void BgWriterNap(void);
-static bool IsCheckpointOnSchedule(double progress);
-static bool ImmediateCheckpointRequested(void);
-static bool CompactBgwriterRequestQueue(void);
 
 /* Signal handlers */
 
 static void bg_quickdie(SIGNAL_ARGS);
 static void BgSigHupHandler(SIGNAL_ARGS);
-static void ReqCheckpointHandler(SIGNAL_ARGS);
 static void ReqShutdownHandler(SIGNAL_ARGS);
 
 
@@ -202,7 +98,6 @@ BackgroundWriterMain(void)
 	sigjmp_buf	local_sigjmp_buf;
 	MemoryContext bgwriter_context;
 
-	BgWriterShmem->bgwriter_pid = MyProcPid;
 	am_bg_writer = true;
 
 	/*
@@ -228,13 +123,13 @@ BackgroundWriterMain(void)
 	 * process to participate in ProcSignal signalling.
 	 */
 	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
-	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
-	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
+	pqsignal(SIGINT, SIG_IGN);			/* as of 9.2 no longer requests checkpoint */
+	pqsignal(SIGTERM, ReqShutdownHandler); 	/* shutdown */
 	pqsignal(SIGQUIT, bg_quickdie);		/* hard crash time */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
-	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
-	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */
+	pqsignal(SIGUSR1, SIG_IGN);			/* reserve for ProcSignal */
+	pqsignal(SIGUSR2, SIG_IGN);			/* request shutdown */
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
@@ -249,11 +144,6 @@ BackgroundWriterMain(void)
 	sigdelset(&BlockSig, SIGQUIT);
 
 	/*
-	 * Initialize so that first time-driven event happens at the correct time.
-	 */
-	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
-
-	/*
 	 * Create a resource owner to keep track of our resources (currently only
 	 * buffer pins).
 	 */
@@ -305,20 +195,6 @@ BackgroundWriterMain(void)
 		AtEOXact_Files();
 		AtEOXact_HashTables(false);
 
-		/* Warn any waiting backends that the checkpoint failed. */
-		if (ckpt_active)
-		{
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_failed++;
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			ckpt_active = false;
-		}
-
 		/*
 		 * Now return to normal top-level context and clear ErrorContext for
 		 * next time.
@@ -361,19 +237,11 @@ BackgroundWriterMain(void)
 	if (RecoveryInProgress())
 		ThisTimeLineID = GetRecoveryTargetTLI();
 
-	/* Do this once before starting the loop, then just at SIGHUP time. */
-	SyncRepUpdateSyncStandbysDefined();
-
 	/*
 	 * Loop forever
 	 */
 	for (;;)
 	{
-		bool		do_checkpoint = false;
-		int			flags = 0;
-		pg_time_t	now;
-		int			elapsed_secs;
-
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -381,23 +249,11 @@ BackgroundWriterMain(void)
 		if (!PostmasterIsAlive())
 			exit(1);
 
-		/*
-		 * Process any requests or signals received recently.
-		 */
-		AbsorbFsyncRequests();
-
 		if (got_SIGHUP)
 		{
 			got_SIGHUP = false;
 			ProcessConfigFile(PGC_SIGHUP);
 			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-		if (checkpoint_requested)
-		{
-			checkpoint_requested = false;
-			do_checkpoint = true;
-			BgWriterStats.m_requested_checkpoints++;
 		}
 		if (shutdown_requested)
 		{
@@ -406,142 +262,14 @@ BackgroundWriterMain(void)
 			 * control back to the sigsetjmp block above
 			 */
 			ExitOnAnyError = true;
-			/* Close down the database */
-			ShutdownXLOG(0, 0);
 			/* Normal exit from the bgwriter is here */
 			proc_exit(0);		/* done */
 		}
 
 		/*
-		 * Force a checkpoint if too much time has elapsed since the last one.
-		 * Note that we count a timed checkpoint in stats only when this
-		 * occurs without an external request, but we set the CAUSE_TIME flag
-		 * bit even if there is also an external request.
+		 * Do one cycle of dirty-buffer writing.
 		 */
-		now = (pg_time_t) time(NULL);
-		elapsed_secs = now - last_checkpoint_time;
-		if (elapsed_secs >= CheckPointTimeout)
-		{
-			if (!do_checkpoint)
-				BgWriterStats.m_timed_checkpoints++;
-			do_checkpoint = true;
-			flags |= CHECKPOINT_CAUSE_TIME;
-		}
-
-		/*
-		 * Do a checkpoint if requested, otherwise do one cycle of
-		 * dirty-buffer writing.
-		 */
-		if (do_checkpoint)
-		{
-			bool		ckpt_performed = false;
-			bool		do_restartpoint;
-
-			/* use volatile pointer to prevent code rearrangement */
-			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-			/*
-			 * Check if we should perform a checkpoint or a restartpoint. As a
-			 * side-effect, RecoveryInProgress() initializes TimeLineID if
-			 * it's not set yet.
-			 */
-			do_restartpoint = RecoveryInProgress();
-
-			/*
-			 * Atomically fetch the request flags to figure out what kind of a
-			 * checkpoint we should perform, and increase the started-counter
-			 * to acknowledge that we've started a new checkpoint.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			flags |= bgs->ckpt_flags;
-			bgs->ckpt_flags = 0;
-			bgs->ckpt_started++;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			/*
-			 * The end-of-recovery checkpoint is a real checkpoint that's
-			 * performed while we're still in recovery.
-			 */
-			if (flags & CHECKPOINT_END_OF_RECOVERY)
-				do_restartpoint = false;
-
-			/*
-			 * We will warn if (a) too soon since last checkpoint (whatever
-			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
-			 * since the last checkpoint start.  Note in particular that this
-			 * implementation will not generate warnings caused by
-			 * CheckPointTimeout < CheckPointWarning.
-			 */
-			if (!do_restartpoint &&
-				(flags & CHECKPOINT_CAUSE_XLOG) &&
-				elapsed_secs < CheckPointWarning)
-				ereport(LOG,
-						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
-				"checkpoints are occurring too frequently (%d seconds apart)",
-									   elapsed_secs,
-									   elapsed_secs),
-						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
-
-			/*
-			 * Initialize bgwriter-private variables used during checkpoint.
-			 */
-			ckpt_active = true;
-			if (!do_restartpoint)
-				ckpt_start_recptr = GetInsertRecPtr();
-			ckpt_start_time = now;
-			ckpt_cached_elapsed = 0;
-
-			/*
-			 * Do the checkpoint.
-			 */
-			if (!do_restartpoint)
-			{
-				CreateCheckPoint(flags);
-				ckpt_performed = true;
-			}
-			else
-				ckpt_performed = CreateRestartPoint(flags);
-
-			/*
-			 * After any checkpoint, close all smgr files.	This is so we
-			 * won't hang onto smgr references to deleted files indefinitely.
-			 */
-			smgrcloseall();
-
-			/*
-			 * Indicate checkpoint completion to any waiting backends.
-			 */
-			SpinLockAcquire(&bgs->ckpt_lck);
-			bgs->ckpt_done = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (ckpt_performed)
-			{
-				/*
-				 * Note we record the checkpoint start time not end time as
-				 * last_checkpoint_time.  This is so that time-driven
-				 * checkpoints happen at a predictable spacing.
-				 */
-				last_checkpoint_time = now;
-			}
-			else
-			{
-				/*
-				 * We were not able to perform the restartpoint (checkpoints
-				 * throw an ERROR in case of error).  Most likely because we
-				 * have not received any new checkpoint WAL records since the
-				 * last restartpoint. Try again in 15 s.
-				 */
-				last_checkpoint_time = now - CheckPointTimeout + 15;
-			}
-
-			ckpt_active = false;
-		}
-		else
-			BgBufferSync();
-
-		/* Check for archive_timeout and switch xlog files if necessary. */
-		CheckArchiveTimeout();
+		BgBufferSync();
 
 		/* Nap for the configured time. */
 		BgWriterNap();
@@ -549,61 +277,6 @@ BackgroundWriterMain(void)
 }
 
 /*
- * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
- *
- * This will switch to a new WAL file and force an archive file write
- * if any activity is recorded in the current WAL file, including just
- * a single checkpoint record.
- */
-static void
-CheckArchiveTimeout(void)
-{
-	pg_time_t	now;
-	pg_time_t	last_time;
-
-	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
-		return;
-
-	now = (pg_time_t) time(NULL);
-
-	/* First we do a quick check using possibly-stale local state. */
-	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
-		return;
-
-	/*
-	 * Update local state ... note that last_xlog_switch_time is the last time
-	 * a switch was performed *or requested*.
-	 */
-	last_time = GetLastSegSwitchTime();
-
-	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
-
-	/* Now we can do the real check */
-	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
-	{
-		XLogRecPtr	switchpoint;
-
-		/* OK, it's time to switch */
-		switchpoint = RequestXLogSwitch();
-
-		/*
-		 * If the returned pointer points exactly to a segment boundary,
-		 * assume nothing happened.
-		 */
-		if ((switchpoint.xrecoff % XLogSegSize) != 0)
-			ereport(DEBUG1,
-				(errmsg("transaction log switch forced (archive_timeout=%d)",
-						XLogArchiveTimeout)));
-
-		/*
-		 * Update state in any case, so we don't retry constantly when the
-		 * system is idle.
-		 */
-		last_xlog_switch_time = now;
-	}
-}
-
-/*
  * BgWriterNap -- Nap for the configured time or until a signal is received.
  */
 static void
@@ -624,185 +297,24 @@ BgWriterNap(void)
 	 * respond reasonably promptly when someone signals us, break down the
 	 * sleep into 1-second increments, and check for interrupts after each
 	 * nap.
-	 *
-	 * We absorb pending requests after each short sleep.
 	 */
-	if (bgwriter_lru_maxpages > 0 || ckpt_active)
+	if (bgwriter_lru_maxpages > 0)
 		udelay = BgWriterDelay * 1000L;
-	else if (XLogArchiveTimeout > 0)
-		udelay = 1000000L;		/* One second */
 	else
 		udelay = 10000000L;		/* Ten seconds */
 
 	while (udelay > 999999L)
 	{
-		if (got_SIGHUP || shutdown_requested ||
-		(ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested))
+		if (got_SIGHUP || shutdown_requested)
 			break;
 		pg_usleep(1000000L);
-		AbsorbFsyncRequests();
 		udelay -= 1000000L;
 	}
 
-	if (!(got_SIGHUP || shutdown_requested ||
-	  (ckpt_active ? ImmediateCheckpointRequested() : checkpoint_requested)))
+	if (!(got_SIGHUP || shutdown_requested))
 		pg_usleep(udelay);
 }
 
-/*
- * Returns true if an immediate checkpoint request is pending.	(Note that
- * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
- * there is one pending behind it.)
- */
-static bool
-ImmediateCheckpointRequested(void)
-{
-	if (checkpoint_requested)
-	{
-		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-
-		/*
-		 * We don't need to acquire the ckpt_lck in this case because we're
-		 * only looking at a single flag bit.
-		 */
-		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
-			return true;
-	}
-	return false;
-}
-
-/*
- * CheckpointWriteDelay -- yield control to bgwriter during a checkpoint
- *
- * This function is called after each page write performed by BufferSync().
- * It is responsible for keeping the bgwriter's normal activities in
- * progress during a long checkpoint, and for throttling BufferSync()'s
- * write rate to hit checkpoint_completion_target.
- *
- * The checkpoint request flags should be passed in; currently the only one
- * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
- *
- * 'progress' is an estimate of how much of the work has been done, as a
- * fraction between 0.0 meaning none, and 1.0 meaning all done.
- */
-void
-CheckpointWriteDelay(int flags, double progress)
-{
-	static int	absorb_counter = WRITES_PER_ABSORB;
-
-	/* Do nothing if checkpoint is being executed by non-bgwriter process */
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * Perform the usual bgwriter duties and take a nap, unless we're behind
-	 * schedule, in which case we just try to catch up as quickly as possible.
-	 */
-	if (!(flags & CHECKPOINT_IMMEDIATE) &&
-		!shutdown_requested &&
-		!ImmediateCheckpointRequested() &&
-		IsCheckpointOnSchedule(progress))
-	{
-		if (got_SIGHUP)
-		{
-			got_SIGHUP = false;
-			ProcessConfigFile(PGC_SIGHUP);
-			/* update global shmem state for sync rep */
-			SyncRepUpdateSyncStandbysDefined();
-		}
-
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-
-		BgBufferSync();
-		CheckArchiveTimeout();
-		BgWriterNap();
-	}
-	else if (--absorb_counter <= 0)
-	{
-		/*
-		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
-		 * operations even when we don't sleep, to prevent overflow of the
-		 * fsync request queue.
-		 */
-		AbsorbFsyncRequests();
-		absorb_counter = WRITES_PER_ABSORB;
-	}
-}
-
-/*
- * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
- *		 in time?
- *
- * Compares the current progress against the time/segments elapsed since last
- * checkpoint, and returns true if the progress we've made this far is greater
- * than the elapsed time/segments.
- */
-static bool
-IsCheckpointOnSchedule(double progress)
-{
-	XLogRecPtr	recptr;
-	struct timeval now;
-	double		elapsed_xlogs,
-				elapsed_time;
-
-	Assert(ckpt_active);
-
-	/* Scale progress according to checkpoint_completion_target. */
-	progress *= CheckPointCompletionTarget;
-
-	/*
-	 * Check against the cached value first. Only do the more expensive
-	 * calculations once we reach the target previously calculated. Since
-	 * neither time or WAL insert pointer moves backwards, a freshly
-	 * calculated value can only be greater than or equal to the cached value.
-	 */
-	if (progress < ckpt_cached_elapsed)
-		return false;
-
-	/*
-	 * Check progress against WAL segments written and checkpoint_segments.
-	 *
-	 * We compare the current WAL insert location against the location
-	 * computed before calling CreateCheckPoint. The code in XLogInsert that
-	 * actually triggers a checkpoint when checkpoint_segments is exceeded
-	 * compares against RedoRecptr, so this is not completely accurate.
-	 * However, it's good enough for our purposes, we're only calculating an
-	 * estimate anyway.
-	 */
-	if (!RecoveryInProgress())
-	{
-		recptr = GetInsertRecPtr();
-		elapsed_xlogs =
-			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
-			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
-			CheckPointSegments;
-
-		if (progress < elapsed_xlogs)
-		{
-			ckpt_cached_elapsed = elapsed_xlogs;
-			return false;
-		}
-	}
-
-	/*
-	 * Check progress against time elapsed and checkpoint_timeout.
-	 */
-	gettimeofday(&now, NULL);
-	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
-					now.tv_usec / 1000000.0) / CheckPointTimeout;
-
-	if (progress < elapsed_time)
-	{
-		ckpt_cached_elapsed = elapsed_time;
-		return false;
-	}
-
-	/* It looks like we're on schedule. */
-	return true;
-}
-
-
 /* --------------------------------
  *		signal handler routines
  * --------------------------------
@@ -847,441 +359,9 @@ BgSigHupHandler(SIGNAL_ARGS)
 	got_SIGHUP = true;
 }
 
-/* SIGINT: set flag to run a normal checkpoint right away */
-static void
-ReqCheckpointHandler(SIGNAL_ARGS)
-{
-	checkpoint_requested = true;
-}
-
 /* SIGUSR2: set flag to run a shutdown checkpoint and exit */
 static void
 ReqShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
 }
-
-
-/* --------------------------------
- *		communication with backends
- * --------------------------------
- */
-
-/*
- * BgWriterShmemSize
- *		Compute space needed for bgwriter-related shared memory
- */
-Size
-BgWriterShmemSize(void)
-{
-	Size		size;
-
-	/*
-	 * Currently, the size of the requests[] array is arbitrarily set equal to
-	 * NBuffers.  This may prove too large or small ...
-	 */
-	size = offsetof(BgWriterShmemStruct, requests);
-	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
-
-	return size;
-}
-
-/*
- * BgWriterShmemInit
- *		Allocate and initialize bgwriter-related shared memory
- */
-void
-BgWriterShmemInit(void)
-{
-	bool		found;
-
-	BgWriterShmem = (BgWriterShmemStruct *)
-		ShmemInitStruct("Background Writer Data",
-						BgWriterShmemSize(),
-						&found);
-
-	if (!found)
-	{
-		/* First time through, so initialize */
-		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
-		SpinLockInit(&BgWriterShmem->ckpt_lck);
-		BgWriterShmem->max_requests = NBuffers;
-	}
-}
-
-/*
- * RequestCheckpoint
- *		Called in backend processes to request a checkpoint
- *
- * flags is a bitwise OR of the following:
- *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
- *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
- *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
- *		ignoring checkpoint_completion_target parameter.
- *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
- *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
- *		CHECKPOINT_END_OF_RECOVERY).
- *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
- *		just signal bgwriter to do it, and return).
- *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
- *		(This affects logging, and in particular enables CheckPointWarning.)
- */
-void
-RequestCheckpoint(int flags)
-{
-	/* use volatile pointer to prevent code rearrangement */
-	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
-	int			ntries;
-	int			old_failed,
-				old_started;
-
-	/*
-	 * If in a standalone backend, just do it ourselves.
-	 */
-	if (!IsPostmasterEnvironment)
-	{
-		/*
-		 * There's no point in doing slow checkpoints in a standalone backend,
-		 * because there's no other backends the checkpoint could disrupt.
-		 */
-		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
-
-		/*
-		 * After any checkpoint, close all smgr files.	This is so we won't
-		 * hang onto smgr references to deleted files indefinitely.
-		 */
-		smgrcloseall();
-
-		return;
-	}
-
-	/*
-	 * Atomically set the request flags, and take a snapshot of the counters.
-	 * When we see ckpt_started > old_started, we know the flags we set here
-	 * have been seen by bgwriter.
-	 *
-	 * Note that we OR the flags with any existing flags, to avoid overriding
-	 * a "stronger" request by another backend.  The flag senses must be
-	 * chosen to make this work!
-	 */
-	SpinLockAcquire(&bgs->ckpt_lck);
-
-	old_failed = bgs->ckpt_failed;
-	old_started = bgs->ckpt_started;
-	bgs->ckpt_flags |= flags;
-
-	SpinLockRelease(&bgs->ckpt_lck);
-
-	/*
-	 * Send signal to request checkpoint.  It's possible that the bgwriter
-	 * hasn't started yet, or is in process of restarting, so we will retry a
-	 * few times if needed.  Also, if not told to wait for the checkpoint to
-	 * occur, we consider failure to send the signal to be nonfatal and merely
-	 * LOG it.
-	 */
-	for (ntries = 0;; ntries++)
-	{
-		if (BgWriterShmem->bgwriter_pid == 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-				"could not request checkpoint because bgwriter not running");
-				break;
-			}
-		}
-		else if (kill(BgWriterShmem->bgwriter_pid, SIGINT) != 0)
-		{
-			if (ntries >= 20)	/* max wait 2.0 sec */
-			{
-				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
-					 "could not signal for checkpoint: %m");
-				break;
-			}
-		}
-		else
-			break;				/* signal sent successfully */
-
-		CHECK_FOR_INTERRUPTS();
-		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
-	}
-
-	/*
-	 * If requested, wait for completion.  We detect completion according to
-	 * the algorithm given above.
-	 */
-	if (flags & CHECKPOINT_WAIT)
-	{
-		int			new_started,
-					new_failed;
-
-		/* Wait for a new checkpoint to start. */
-		for (;;)
-		{
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_started = bgs->ckpt_started;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_started != old_started)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		/*
-		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
-		 */
-		for (;;)
-		{
-			int			new_done;
-
-			SpinLockAcquire(&bgs->ckpt_lck);
-			new_done = bgs->ckpt_done;
-			new_failed = bgs->ckpt_failed;
-			SpinLockRelease(&bgs->ckpt_lck);
-
-			if (new_done - new_started >= 0)
-				break;
-
-			CHECK_FOR_INTERRUPTS();
-			pg_usleep(100000L);
-		}
-
-		if (new_failed != old_failed)
-			ereport(ERROR,
-					(errmsg("checkpoint request failed"),
-					 errhint("Consult recent messages in the server log for details.")));
-	}
-}
-
-/*
- * ForwardFsyncRequest
- *		Forward a file-fsync request from a backend to the bgwriter
- *
- * Whenever a backend is compelled to write directly to a relation
- * (which should be seldom, if the bgwriter is getting its job done),
- * the backend calls this routine to pass over knowledge that the relation
- * is dirty and must be fsync'd before next checkpoint.  We also use this
- * opportunity to count such writes for statistical purposes.
- *
- * segno specifies which segment (not block!) of the relation needs to be
- * fsync'd.  (Since the valid range is much less than BlockNumber, we can
- * use high values for special flags; that's all internal to md.c, which
- * see for details.)
- *
- * To avoid holding the lock for longer than necessary, we normally write
- * to the requests[] queue without checking for duplicates.  The bgwriter
- * will have to eliminate dups internally anyway.  However, if we discover
- * that the queue is full, we make a pass over the entire queue to compact
- * it.	This is somewhat expensive, but the alternative is for the backend
- * to perform its own fsync, which is far more expensive in practice.  It
- * is theoretically possible a backend fsync might still be necessary, if
- * the queue is full and contains no duplicate entries.  In that case, we
- * let the backend know by returning false.
- */
-bool
-ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
-					BlockNumber segno)
-{
-	BgWriterRequest *request;
-
-	if (!IsUnderPostmaster)
-		return false;			/* probably shouldn't even get here */
-
-	if (am_bg_writer)
-		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
-
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Count all backend writes regardless of if they fit in the queue */
-	BgWriterShmem->num_backend_writes++;
-
-	/*
-	 * If the background writer isn't running or the request queue is full,
-	 * the backend will have to perform its own fsync request.	But before
-	 * forcing that to happen, we can try to compact the background writer
-	 * request queue.
-	 */
-	if (BgWriterShmem->bgwriter_pid == 0 ||
-		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
-		 && !CompactBgwriterRequestQueue()))
-	{
-		/*
-		 * Count the subset of writes where backends have to do their own
-		 * fsync
-		 */
-		BgWriterShmem->num_backend_fsync++;
-		LWLockRelease(BgWriterCommLock);
-		return false;
-	}
-	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
-	request->rnode = rnode;
-	request->forknum = forknum;
-	request->segno = segno;
-	LWLockRelease(BgWriterCommLock);
-	return true;
-}
-
-/*
- * CompactBgwriterRequestQueue
- *		Remove duplicates from the request queue to avoid backend fsyncs.
- *
- * Although a full fsync request queue is not common, it can lead to severe
- * performance problems when it does happen.  So far, this situation has
- * only been observed to occur when the system is under heavy write load,
- * and especially during the "sync" phase of a checkpoint.	Without this
- * logic, each backend begins doing an fsync for every block written, which
- * gets very expensive and can slow down the whole system.
- *
- * Trying to do this every time the queue is full could lose if there
- * aren't any removable entries.  But should be vanishingly rare in
- * practice: there's one queue entry per shared buffer.
- */
-static bool
-CompactBgwriterRequestQueue()
-{
-	struct BgWriterSlotMapping
-	{
-		BgWriterRequest request;
-		int			slot;
-	};
-
-	int			n,
-				preserve_count;
-	int			num_skipped = 0;
-	HASHCTL		ctl;
-	HTAB	   *htab;
-	bool	   *skip_slot;
-
-	/* must hold BgWriterCommLock in exclusive mode */
-	Assert(LWLockHeldByMe(BgWriterCommLock));
-
-	/* Initialize temporary hash table */
-	MemSet(&ctl, 0, sizeof(ctl));
-	ctl.keysize = sizeof(BgWriterRequest);
-	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
-	ctl.hash = tag_hash;
-	htab = hash_create("CompactBgwriterRequestQueue",
-					   BgWriterShmem->num_requests,
-					   &ctl,
-					   HASH_ELEM | HASH_FUNCTION);
-
-	/* Initialize skip_slot array */
-	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
-
-	/*
-	 * The basic idea here is that a request can be skipped if it's followed
-	 * by a later, identical request.  It might seem more sensible to work
-	 * backwards from the end of the queue and check whether a request is
-	 * *preceded* by an earlier, identical request, in the hopes of doing less
-	 * copying.  But that might change the semantics, if there's an
-	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
-	 * we do it this way.  It would be possible to be even smarter if we made
-	 * the code below understand the specific semantics of such requests (it
-	 * could blow away preceding entries that would end up being canceled
-	 * anyhow), but it's not clear that the extra complexity would buy us
-	 * anything.
-	 */
-	for (n = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		BgWriterRequest *request;
-		struct BgWriterSlotMapping *slotmap;
-		bool		found;
-
-		request = &BgWriterShmem->requests[n];
-		slotmap = hash_search(htab, request, HASH_ENTER, &found);
-		if (found)
-		{
-			skip_slot[slotmap->slot] = true;
-			++num_skipped;
-		}
-		slotmap->slot = n;
-	}
-
-	/* Done with the hash table. */
-	hash_destroy(htab);
-
-	/* If no duplicates, we're out of luck. */
-	if (!num_skipped)
-	{
-		pfree(skip_slot);
-		return false;
-	}
-
-	/* We found some duplicates; remove them. */
-	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
-	{
-		if (skip_slot[n])
-			continue;
-		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
-	}
-	ereport(DEBUG1,
-	   (errmsg("compacted fsync request queue from %d entries to %d entries",
-			   BgWriterShmem->num_requests, preserve_count)));
-	BgWriterShmem->num_requests = preserve_count;
-
-	/* Cleanup. */
-	pfree(skip_slot);
-	return true;
-}
-
-/*
- * AbsorbFsyncRequests
- *		Retrieve queued fsync requests and pass them to local smgr.
- *
- * This is exported because it must be called during CreateCheckPoint;
- * we have to be sure we have accepted all pending requests just before
- * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
- * non-bgwriter processes, do nothing if not bgwriter.
- */
-void
-AbsorbFsyncRequests(void)
-{
-	BgWriterRequest *requests = NULL;
-	BgWriterRequest *request;
-	int			n;
-
-	if (!am_bg_writer)
-		return;
-
-	/*
-	 * We have to PANIC if we fail to absorb all the pending requests (eg,
-	 * because our hashtable runs out of memory).  This is because the system
-	 * cannot run safely if we are unable to fsync what we have been told to
-	 * fsync.  Fortunately, the hashtable is so small that the problem is
-	 * quite unlikely to arise in practice.
-	 */
-	START_CRIT_SECTION();
-
-	/*
-	 * We try to avoid holding the lock for a long time by copying the request
-	 * array.
-	 */
-	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
-
-	/* Transfer write count into pending pgstats message */
-	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
-	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
-
-	BgWriterShmem->num_backend_writes = 0;
-	BgWriterShmem->num_backend_fsync = 0;
-
-	n = BgWriterShmem->num_requests;
-	if (n > 0)
-	{
-		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
-		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
-	}
-	BgWriterShmem->num_requests = 0;
-
-	LWLockRelease(BgWriterCommLock);
-
-	for (request = requests; n > 0; request++, n--)
-		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
-
-	if (requests)
-		pfree(requests);
-
-	END_CRIT_SECTION();
-}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
new file mode 100644
index 0000000..6c17c26
--- /dev/null
+++ b/src/backend/postmaster/checkpointer.c
@@ -0,0 +1,1236 @@
+/*-------------------------------------------------------------------------
+ *
+ * checkpointer.c
+ *
+ * The checkpointer is new as of Postgres 9.2.  It handles all checkpoints.
+ * Checkpoints are automatically dispatched after a certain amount of time has
+ * elapsed since the last one, and it can be signaled to perform requested
+ * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
+ * so many WAL segments is implemented by having backends signal when they
+ * fill WAL segments; the checkpointer itself doesn't watch for the
+ * condition.)
+ *
+ * The checkpointer is started by the postmaster as soon as the startup subprocess
+ * finishes, or as soon as recovery begins if we are doing archive recovery.
+ * It remains alive until the postmaster commands it to terminate.
+ * Normal termination is by SIGUSR2, which instructs the checkpointer to execute
+ * a shutdown checkpoint and then exit(0).	(All backends must be stopped
+ * before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT; like any
+ * backend, the checkpointer will simply abort and exit on SIGQUIT.
+ *
+ * If the checkpointer exits unexpectedly, the postmaster treats that the same
+ * as a backend crash: shared memory may be corrupted, so remaining backends
+ * should be killed by SIGQUIT and then a recovery cycle started.  (Even if
+ * shared memory isn't corrupted, we have lost information about which
+ * files need to be fsync'd for the next checkpoint, and so a system
+ * restart needs to be forced.)
+ *
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/checkpointer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <signal.h>
+#include <sys/time.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "access/xlog_internal.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgwriter.h"
+#include "replication/syncrep.h"
+#include "storage/bufmgr.h"
+#include "storage/ipc.h"
+#include "storage/lwlock.h"
+#include "storage/pmsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+
+/*----------
+ * Shared memory area for communication between checkpointer and backends
+ *
+ * The ckpt counters allow backends to watch for completion of a checkpoint
+ * request they send.  Here's how it works:
+ *	* At start of a checkpoint, checkpointer reads (and clears) the request flags
+ *	  and increments ckpt_started, while holding ckpt_lck.
+ *	* On completion of a checkpoint, checkpointer sets ckpt_done to
+ *	  equal ckpt_started.
+ *	* On failure of a checkpoint, checkpointer increments ckpt_failed
+ *	  and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ *	1. Record current values of ckpt_failed and ckpt_started, and
+ *	   set request flags, while holding ckpt_lck.
+ *	2. Send signal to request checkpoint.
+ *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
+ *	   begun since you started this algorithm (although *not* that it was
+ *	   specifically initiated by your signal), and that it is using your flags.
+ *	4. Record new value of ckpt_started.
+ *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
+ *	   arithmetic here in case counters wrap around.)  Now you know a
+ *	   checkpoint has started and completed, but not whether it was
+ *	   successful.
+ *	6. If ckpt_failed is different from the originally saved value,
+ *	   assume request failed; otherwise it was definitely successful.
+ *
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start.  The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by non-bgwriter processes.  This counter should be wide enough that it
+ * can't overflow during a single bgwriter cycle.  num_backend_fsync
+ * counts the subset of those writes that also had to do their own fsync,
+ * because the background writer failed to absorb their request.
+ *
+ * The requests array holds fsync requests sent by backends and not yet
+ * absorbed by the checkpointer.
+ *
+ * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
+ * the requests fields are protected by BgWriterCommLock.
+ *----------
+ */
+typedef struct
+{
+	RelFileNodeBackend rnode;
+	ForkNumber	forknum;
+	BlockNumber segno;			/* see md.c for special values */
+	/* might add a real request-type field later; not needed yet */
+} BgWriterRequest;
+
+typedef struct
+{
+	pid_t		checkpointer_pid;	/* PID of bgwriter (0 if not started) */
+
+	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
+
+	int			ckpt_started;	/* advances when checkpoint starts */
+	int			ckpt_done;		/* advances when checkpoint done */
+	int			ckpt_failed;	/* advances when checkpoint fails */
+
+	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
+
+	uint32		num_backend_writes;		/* counts non-bgwriter buffer writes */
+	uint32		num_backend_fsync;		/* counts non-bgwriter fsync calls */
+
+	int			num_requests;	/* current # of requests */
+	int			max_requests;	/* allocated array size */
+	BgWriterRequest requests[1];	/* VARIABLE LENGTH ARRAY */
+} BgWriterShmemStruct;
+
+static BgWriterShmemStruct *BgWriterShmem;
+
+/* interval for calling AbsorbFsyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB		1000
+
+/*
+ * GUC parameters
+ */
+int			CheckPointTimeout = 300;
+int			CheckPointWarning = 30;
+double		CheckPointCompletionTarget = 0.5;
+
+/*
+ * Flags set by interrupt handlers for later service in the main loop.
+ */
+static volatile sig_atomic_t got_SIGHUP = false;
+static volatile sig_atomic_t checkpoint_requested = false;
+static volatile sig_atomic_t shutdown_requested = false;
+
+/*
+ * Private state
+ */
+static bool am_checkpointer = false;
+
+static bool ckpt_active = false;
+
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void CheckArchiveTimeout(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+static bool CompactCheckpointerRequestQueue(void);
+
+/* Signal handlers */
+
+static void chkpt_quickdie(SIGNAL_ARGS);
+static void ChkptSigHupHandler(SIGNAL_ARGS);
+static void ReqCheckpointHandler(SIGNAL_ARGS);
+static void ReqShutdownHandler(SIGNAL_ARGS);
+
+
+/*
+ * Main entry point for checkpointer process
+ *
+ * This is invoked from BootstrapMain, which has already created the basic
+ * execution environment, but not enabled signals yet.
+ */
+void
+CheckpointerMain(void)
+{
+	sigjmp_buf	local_sigjmp_buf;
+	MemoryContext checkpointer_context;
+
+	BgWriterShmem->checkpointer_pid = MyProcPid;
+	am_checkpointer = true;
+
+	/*
+	 * If possible, make this process a group leader, so that the postmaster
+	 * can signal any child processes too.	(checkpointer probably never has any
+	 * child processes, but for consistency we make all postmaster child
+	 * processes do this.)
+	 */
+#ifdef HAVE_SETSID
+	if (setsid() < 0)
+		elog(FATAL, "setsid() failed: %m");
+#endif
+
+	/*
+	 * Properly accept or ignore signals the postmaster might send us
+	 *
+	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
+	 * system shutdown cycle, init will SIGTERM all processes at once.	We
+	 * want to wait for the backends to exit, whereupon the postmaster will
+	 * tell us it's okay to shut down (via SIGUSR2).
+	 *
+	 * SIGUSR1 is presently unused; keep it spare in case someday we want this
+	 * process to participate in ProcSignal signalling.
+	 */
+	pqsignal(SIGHUP, ChkptSigHupHandler);	/* set flag to read config file */
+	pqsignal(SIGINT, ReqCheckpointHandler);	/* request checkpoint */
+	pqsignal(SIGTERM, SIG_IGN);				/* ignore SIGTERM */
+	pqsignal(SIGQUIT, chkpt_quickdie);		/* hard crash time */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
+	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */
+
+	/*
+	 * Reset some signals that are accepted by postmaster but not here
+	 */
+	pqsignal(SIGCHLD, SIG_DFL);
+	pqsignal(SIGTTIN, SIG_DFL);
+	pqsignal(SIGTTOU, SIG_DFL);
+	pqsignal(SIGCONT, SIG_DFL);
+	pqsignal(SIGWINCH, SIG_DFL);
+
+	/* We allow SIGQUIT (quickdie) at all times */
+	sigdelset(&BlockSig, SIGQUIT);
+
+	/*
+	 * Initialize so that first time-driven event happens at the correct time.
+	 */
+	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);
+
+	/*
+	 * Create a resource owner to keep track of our resources (currently only
+	 * buffer pins).
+	 */
+	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer");
+
+	/*
+	 * Create a memory context that we will do all our work in.  We do this so
+	 * that we can reset the context during error recovery and thereby avoid
+	 * possible memory leaks.  Formerly this code just ran in
+	 * TopMemoryContext, but resetting that would be a really bad idea.
+	 */
+	checkpointer_context = AllocSetContextCreate(TopMemoryContext,
+											 "Checkpointer",
+											 ALLOCSET_DEFAULT_MINSIZE,
+											 ALLOCSET_DEFAULT_INITSIZE,
+											 ALLOCSET_DEFAULT_MAXSIZE);
+	MemoryContextSwitchTo(checkpointer_context);
+
+	/*
+	 * If an exception is encountered, processing resumes here.
+	 *
+	 * See notes in postgres.c about the design of this coding.
+	 */
+	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
+	{
+		/* Since not using PG_TRY, must reset error stack by hand */
+		error_context_stack = NULL;
+
+		/* Prevent interrupts while cleaning up */
+		HOLD_INTERRUPTS();
+
+		/* Report the error to the server log */
+		EmitErrorReport();
+
+		/*
+		 * These operations are really just a minimal subset of
+		 * AbortTransaction().	We don't have very many resources to worry
+		 * about in checkpointer, but we do have LWLocks, buffers, and temp files.
+		 */
+		LWLockReleaseAll();
+		AbortBufferIO();
+		UnlockBuffers();
+		/* buffer pins are released here: */
+		ResourceOwnerRelease(CurrentResourceOwner,
+							 RESOURCE_RELEASE_BEFORE_LOCKS,
+							 false, true);
+		/* we needn't bother with the other ResourceOwnerRelease phases */
+		AtEOXact_Buffers(false);
+		AtEOXact_Files();
+		AtEOXact_HashTables(false);
+
+		/* Warn any waiting backends that the checkpoint failed. */
+		if (ckpt_active)
+		{
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_failed++;
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Now return to normal top-level context and clear ErrorContext for
+		 * next time.
+		 */
+		MemoryContextSwitchTo(checkpointer_context);
+		FlushErrorState();
+
+		/* Flush any leaked data in the top-level context */
+		MemoryContextResetAndDeleteChildren(checkpointer_context);
+
+		/* Now we can allow interrupts again */
+		RESUME_INTERRUPTS();
+
+		/*
+		 * Sleep at least 1 second after any error.  A write error is likely
+		 * to be repeated, and we don't want to be filling the error logs as
+		 * fast as we can.
+		 */
+		pg_usleep(1000000L);
+
+		/*
+		 * Close all open files after any error.  This is helpful on Windows,
+		 * where holding deleted files open causes various strange errors.
+		 * It's not clear we need it elsewhere, but shouldn't hurt.
+		 */
+		smgrcloseall();
+	}
+
+	/* We can now handle ereport(ERROR) */
+	PG_exception_stack = &local_sigjmp_buf;
+
+	/*
+	 * Unblock signals (they were blocked when the postmaster forked us)
+	 */
+	PG_SETMASK(&UnBlockSig);
+
+	/*
+	 * Use the recovery target timeline ID during recovery
+	 */
+	if (RecoveryInProgress())
+		ThisTimeLineID = GetRecoveryTargetTLI();
+
+	/* Do this once before starting the loop, then just at SIGHUP time. */
+	SyncRepUpdateSyncStandbysDefined();
+
+	/*
+	 * Loop forever
+	 */
+	for (;;)
+	{
+		bool		do_checkpoint = false;
+		int			flags = 0;
+		pg_time_t	now;
+		int			elapsed_secs;
+
+		/*
+		 * Emergency bailout if postmaster has died.  This is to avoid the
+		 * necessity for manual cleanup of all postmaster children.
+		 */
+		if (!PostmasterIsAlive())
+			exit(1);
+
+		/*
+		 * Process any requests or signals received recently.
+		 */
+		AbsorbFsyncRequests();
+
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+		if (checkpoint_requested)
+		{
+			checkpoint_requested = false;
+			do_checkpoint = true;
+			BgWriterStats.m_requested_checkpoints++;
+		}
+		if (shutdown_requested)
+		{
+			/*
+			 * From here on, elog(ERROR) should end with exit(1), not send
+			 * control back to the sigsetjmp block above
+			 */
+			ExitOnAnyError = true;
+			/* Close down the database */
+			ShutdownXLOG(0, 0);
+			/* Normal exit from the checkpointer is here */
+			proc_exit(0);		/* done */
+		}
+
+		/*
+		 * Force a checkpoint if too much time has elapsed since the last one.
+		 * Note that we count a timed checkpoint in stats only when this
+		 * occurs without an external request, but we set the CAUSE_TIME flag
+		 * bit even if there is also an external request.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+		{
+			if (!do_checkpoint)
+				BgWriterStats.m_timed_checkpoints++;
+			do_checkpoint = true;
+			flags |= CHECKPOINT_CAUSE_TIME;
+		}
+
+		/*
+		 * Do a checkpoint if requested.
+		 */
+		if (do_checkpoint)
+		{
+			bool		ckpt_performed = false;
+			bool		do_restartpoint;
+
+			/* use volatile pointer to prevent code rearrangement */
+			volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+			/*
+			 * Check if we should perform a checkpoint or a restartpoint. As a
+			 * side-effect, RecoveryInProgress() initializes TimeLineID if
+			 * it's not set yet.
+			 */
+			do_restartpoint = RecoveryInProgress();
+
+			/*
+			 * Atomically fetch the request flags to figure out what kind of a
+			 * checkpoint we should perform, and increase the started-counter
+			 * to acknowledge that we've started a new checkpoint.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			flags |= bgs->ckpt_flags;
+			bgs->ckpt_flags = 0;
+			bgs->ckpt_started++;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			/*
+			 * The end-of-recovery checkpoint is a real checkpoint that's
+			 * performed while we're still in recovery.
+			 */
+			if (flags & CHECKPOINT_END_OF_RECOVERY)
+				do_restartpoint = false;
+
+			/*
+			 * We will warn if (a) too soon since last checkpoint (whatever
+			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+			 * since the last checkpoint start.  Note in particular that this
+			 * implementation will not generate warnings caused by
+			 * CheckPointTimeout < CheckPointWarning.
+			 */
+			if (!do_restartpoint &&
+				(flags & CHECKPOINT_CAUSE_XLOG) &&
+				elapsed_secs < CheckPointWarning)
+				ereport(LOG,
+						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+				"checkpoints are occurring too frequently (%d seconds apart)",
+									   elapsed_secs,
+									   elapsed_secs),
+						 errhint("Consider increasing the configuration parameter \"checkpoint_segments\".")));
+
+			/*
+			 * Initialize checkpointer-private variables used during checkpoint.
+			 */
+			ckpt_active = true;
+			if (!do_restartpoint)
+				ckpt_start_recptr = GetInsertRecPtr();
+			ckpt_start_time = now;
+			ckpt_cached_elapsed = 0;
+
+			/*
+			 * Do the checkpoint.
+			 */
+			if (!do_restartpoint)
+			{
+				CreateCheckPoint(flags);
+				ckpt_performed = true;
+			}
+			else
+				ckpt_performed = CreateRestartPoint(flags);
+
+			/*
+			 * After any checkpoint, close all smgr files.	This is so we
+			 * won't hang onto smgr references to deleted files indefinitely.
+			 */
+			smgrcloseall();
+
+			/*
+			 * Indicate checkpoint completion to any waiting backends.
+			 */
+			SpinLockAcquire(&bgs->ckpt_lck);
+			bgs->ckpt_done = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (ckpt_performed)
+			{
+				/*
+				 * Note we record the checkpoint start time not end time as
+				 * last_checkpoint_time.  This is so that time-driven
+				 * checkpoints happen at a predictable spacing.
+				 */
+				last_checkpoint_time = now;
+			}
+			else
+			{
+				/*
+				 * We were not able to perform the restartpoint (checkpoints
+				 * throw an ERROR in case of error).  Most likely because we
+				 * have not received any new checkpoint WAL records since the
+				 * last restartpoint. Try again in 15 s.
+				 */
+				last_checkpoint_time = now - CheckPointTimeout + 15;
+			}
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Nap for a while and then loop again. Later patches will replace
+		 * this with a latch loop. Keep it simple now for clarity.
+		 * Relatively long sleep because the bgwriter does cleanup now.
+		 */
+		pg_usleep(500000L);
+
+		/* Check for archive_timeout and switch xlog files if necessary. */
+		CheckArchiveTimeout();
+	}
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ *
+ * This will switch to a new WAL file and force an archive file write
+ * if any activity is recorded in the current WAL file, including just
+ * a single checkpoint record.
+ */
+static void
+CheckArchiveTimeout(void)
+{
+	pg_time_t	now;
+	pg_time_t	last_time;
+
+	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+		return;
+
+	now = (pg_time_t) time(NULL);
+
+	/* First we do a quick check using possibly-stale local state. */
+	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+		return;
+
+	/*
+	 * Update local state ... note that last_xlog_switch_time is the last time
+	 * a switch was performed *or requested*.
+	 */
+	last_time = GetLastSegSwitchTime();
+
+	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+	/* Now we can do the real check */
+	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+	{
+		XLogRecPtr	switchpoint;
+
+		/* OK, it's time to switch */
+		switchpoint = RequestXLogSwitch();
+
+		/*
+		 * If the returned pointer points exactly to a segment boundary,
+		 * assume nothing happened.
+		 */
+		if ((switchpoint.xrecoff % XLogSegSize) != 0)
+			ereport(DEBUG1,
+				(errmsg("transaction log switch forced (archive_timeout=%d)",
+						XLogArchiveTimeout)));
+
+		/*
+		 * Update state in any case, so we don't retry constantly when the
+		 * system is idle.
+		 */
+		last_xlog_switch_time = now;
+	}
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending.	(Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+	if (checkpoint_requested)
+	{
+		volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+
+		/*
+		 * We don't need to acquire the ckpt_lck in this case because we're
+		 * only looking at a single flag bit.
+		 */
+		if (bgs->ckpt_flags & CHECKPOINT_IMMEDIATE)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * CheckpointWriteDelay -- control rate of checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for throttling BufferSync()'s write rate to hit
+ * checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+	static int	absorb_counter = WRITES_PER_ABSORB;
+
+	/* Do nothing if checkpoint is being executed by non-checkpointer process */
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * Perform the usual duties and take a nap, unless we're behind
+	 * schedule, in which case we just try to catch up as quickly as possible.
+	 */
+	if (!(flags & CHECKPOINT_IMMEDIATE) &&
+		!shutdown_requested &&
+		!ImmediateCheckpointRequested() &&
+		IsCheckpointOnSchedule(progress))
+	{
+		if (got_SIGHUP)
+		{
+			got_SIGHUP = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update global shmem state for sync rep */
+			SyncRepUpdateSyncStandbysDefined();
+		}
+
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+
+		CheckArchiveTimeout();
+
+		/*
+		 * Checkpoint sleep used to be connected to bgwriter_delay at 200ms.
+		 * That resulted in more frequent wakeups if not much work to do.
+		 * Checkpointer and bgwriter are no longer related so take the Big Sleep.
+		 */
+		pg_usleep(100000L);
+	}
+	else if (--absorb_counter <= 0)
+	{
+		/*
+		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+		 * operations even when we don't sleep, to prevent overflow of the
+		 * fsync request queue.
+		 */
+		AbsorbFsyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+	}
+}
+
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ *		 in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+	XLogRecPtr	recptr;
+	struct timeval now;
+	double		elapsed_xlogs,
+				elapsed_time;
+
+	Assert(ckpt_active);
+
+	/* Scale progress according to checkpoint_completion_target. */
+	progress *= CheckPointCompletionTarget;
+
+	/*
+	 * Check against the cached value first. Only do the more expensive
+	 * calculations once we reach the target previously calculated. Since
+	 * neither time or WAL insert pointer moves backwards, a freshly
+	 * calculated value can only be greater than or equal to the cached value.
+	 */
+	if (progress < ckpt_cached_elapsed)
+		return false;
+
+	/*
+	 * Check progress against WAL segments written and checkpoint_segments.
+	 *
+	 * We compare the current WAL insert location against the location
+	 * computed before calling CreateCheckPoint. The code in XLogInsert that
+	 * actually triggers a checkpoint when checkpoint_segments is exceeded
+	 * compares against RedoRecptr, so this is not completely accurate.
+	 * However, it's good enough for our purposes, we're only calculating an
+	 * estimate anyway.
+	 */
+	if (!RecoveryInProgress())
+	{
+		recptr = GetInsertRecPtr();
+		elapsed_xlogs =
+			(((double) (int32) (recptr.xlogid - ckpt_start_recptr.xlogid)) * XLogSegsPerFile +
+			 ((double) recptr.xrecoff - (double) ckpt_start_recptr.xrecoff) / XLogSegSize) /
+			CheckPointSegments;
+
+		if (progress < elapsed_xlogs)
+		{
+			ckpt_cached_elapsed = elapsed_xlogs;
+			return false;
+		}
+	}
+
+	/*
+	 * Check progress against time elapsed and checkpoint_timeout.
+	 */
+	gettimeofday(&now, NULL);
+	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+					now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+	if (progress < elapsed_time)
+	{
+		ckpt_cached_elapsed = elapsed_time;
+		return false;
+	}
+
+	/* It looks like we're on schedule. */
+	return true;
+}
+
+
+/* --------------------------------
+ *		signal handler routines
+ * --------------------------------
+ */
+
+/*
+ * chkpt_quickdie() occurs when signalled SIGQUIT by the postmaster.
+ *
+ * Some backend has bought the farm,
+ * so we need to stop what we're doing and exit.
+ */
+static void
+chkpt_quickdie(SIGNAL_ARGS)
+{
+	PG_SETMASK(&BlockSig);
+
+	/*
+	 * We DO NOT want to run proc_exit() callbacks -- we're here because
+	 * shared memory may be corrupted, so we don't want to try to clean up our
+	 * transaction.  Just nail the windows shut and get out of town.  Now that
+	 * there's an atexit callback to prevent third-party code from breaking
+	 * things by calling exit() directly, we have to reset the callbacks
+	 * explicitly to make this work as intended.
+	 */
+	on_exit_reset();
+
+	/*
+	 * Note we do exit(2) not exit(0).	This is to force the postmaster into a
+	 * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
+	 * backend.  This is necessary precisely because we don't clean up our
+	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
+	 * should ensure the postmaster sees this as a crash, too, but no harm in
+	 * being doubly sure.)
+	 */
+	exit(2);
+}
+
+/* SIGHUP: set flag to re-read config file at next convenient time */
+static void
+ChkptSigHupHandler(SIGNAL_ARGS)
+{
+	got_SIGHUP = true;
+}
+
+/* SIGINT: set flag to run a normal checkpoint right away */
+static void
+ReqCheckpointHandler(SIGNAL_ARGS)
+{
+	checkpoint_requested = true;
+}
+
+/* SIGUSR2: set flag to run a shutdown checkpoint and exit */
+static void
+ReqShutdownHandler(SIGNAL_ARGS)
+{
+	shutdown_requested = true;
+}
+
+
+/* --------------------------------
+ *		communication with backends
+ * --------------------------------
+ */
+
+/*
+ * BgWriterShmemSize
+ *		Compute space needed for bgwriter-related shared memory
+ */
+Size
+BgWriterShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Currently, the size of the requests[] array is arbitrarily set equal to
+	 * NBuffers.  This may prove too large or small ...
+	 */
+	size = offsetof(BgWriterShmemStruct, requests);
+	size = add_size(size, mul_size(NBuffers, sizeof(BgWriterRequest)));
+
+	return size;
+}
+
+/*
+ * BgWriterShmemInit
+ *		Allocate and initialize bgwriter-related shared memory
+ */
+void
+BgWriterShmemInit(void)
+{
+	bool		found;
+
+	BgWriterShmem = (BgWriterShmemStruct *)
+		ShmemInitStruct("Background Writer Data",
+						BgWriterShmemSize(),
+						&found);
+
+	if (!found)
+	{
+		/* First time through, so initialize */
+		MemSet(BgWriterShmem, 0, sizeof(BgWriterShmemStruct));
+		SpinLockInit(&BgWriterShmem->ckpt_lck);
+		BgWriterShmem->max_requests = NBuffers;
+	}
+}
+
+/*
+ * RequestCheckpoint
+ *		Called in backend processes to request a checkpoint
+ *
+ * flags is a bitwise OR of the following:
+ *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ *		ignoring checkpoint_completion_target parameter.
+ *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occured
+ *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ *		CHECKPOINT_END_OF_RECOVERY).
+ *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ *		just signal bgwriter to do it, and return).
+ *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ *		(This affects logging, and in particular enables CheckPointWarning.)
+ */
+void
+RequestCheckpoint(int flags)
+{
+	/* use volatile pointer to prevent code rearrangement */
+	volatile BgWriterShmemStruct *bgs = BgWriterShmem;
+	int			ntries;
+	int			old_failed,
+				old_started;
+
+	/*
+	 * If in a standalone backend, just do it ourselves.
+	 */
+	if (!IsPostmasterEnvironment)
+	{
+		/*
+		 * There's no point in doing slow checkpoints in a standalone backend,
+		 * because there's no other backends the checkpoint could disrupt.
+		 */
+		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
+
+		/*
+		 * After any checkpoint, close all smgr files.	This is so we won't
+		 * hang onto smgr references to deleted files indefinitely.
+		 */
+		smgrcloseall();
+
+		return;
+	}
+
+	/*
+	 * Atomically set the request flags, and take a snapshot of the counters.
+	 * When we see ckpt_started > old_started, we know the flags we set here
+	 * have been seen by bgwriter.
+	 *
+	 * Note that we OR the flags with any existing flags, to avoid overriding
+	 * a "stronger" request by another backend.  The flag senses must be
+	 * chosen to make this work!
+	 */
+	SpinLockAcquire(&bgs->ckpt_lck);
+
+	old_failed = bgs->ckpt_failed;
+	old_started = bgs->ckpt_started;
+	bgs->ckpt_flags |= flags;
+
+	SpinLockRelease(&bgs->ckpt_lck);
+
+	/*
+	 * Send signal to request checkpoint.  It's possible that the bgwriter
+	 * hasn't started yet, or is in process of restarting, so we will retry a
+	 * few times if needed.  Also, if not told to wait for the checkpoint to
+	 * occur, we consider failure to send the signal to be nonfatal and merely
+	 * LOG it.
+	 */
+	for (ntries = 0;; ntries++)
+	{
+		if (BgWriterShmem->checkpointer_pid == 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+				"could not request checkpoint because checkpointer not running");
+				break;
+			}
+		}
+		else if (kill(BgWriterShmem->checkpointer_pid, SIGINT) != 0)
+		{
+			if (ntries >= 20)	/* max wait 2.0 sec */
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: %m");
+				break;
+			}
+		}
+		else
+			break;				/* signal sent successfully */
+
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
+	}
+
+	/*
+	 * If requested, wait for completion.  We detect completion according to
+	 * the algorithm given above.
+	 */
+	if (flags & CHECKPOINT_WAIT)
+	{
+		int			new_started,
+					new_failed;
+
+		/* Wait for a new checkpoint to start. */
+		for (;;)
+		{
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_started = bgs->ckpt_started;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_started != old_started)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		/*
+		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
+		 */
+		for (;;)
+		{
+			int			new_done;
+
+			SpinLockAcquire(&bgs->ckpt_lck);
+			new_done = bgs->ckpt_done;
+			new_failed = bgs->ckpt_failed;
+			SpinLockRelease(&bgs->ckpt_lck);
+
+			if (new_done - new_started >= 0)
+				break;
+
+			CHECK_FOR_INTERRUPTS();
+			pg_usleep(100000L);
+		}
+
+		if (new_failed != old_failed)
+			ereport(ERROR,
+					(errmsg("checkpoint request failed"),
+					 errhint("Consult recent messages in the server log for details.")));
+	}
+}
+
+/*
+ * ForwardFsyncRequest
+ *		Forward a file-fsync request from a backend to the bgwriter
+ *
+ * Whenever a backend is compelled to write directly to a relation
+ * (which should be seldom, if the bgwriter is getting its job done),
+ * the backend calls this routine to pass over knowledge that the relation
+ * is dirty and must be fsync'd before next checkpoint.  We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * segno specifies which segment (not block!) of the relation needs to be
+ * fsync'd.  (Since the valid range is much less than BlockNumber, we can
+ * use high values for special flags; that's all internal to md.c, which
+ * see for details.)
+ *
+ * To avoid holding the lock for longer than necessary, we normally write
+ * to the requests[] queue without checking for duplicates.  The bgwriter
+ * will have to eliminate dups internally anyway.  However, if we discover
+ * that the queue is full, we make a pass over the entire queue to compact
+ * it.	This is somewhat expensive, but the alternative is for the backend
+ * to perform its own fsync, which is far more expensive in practice.  It
+ * is theoretically possible a backend fsync might still be necessary, if
+ * the queue is full and contains no duplicate entries.  In that case, we
+ * let the backend know by returning false.
+ */
+bool
+ForwardFsyncRequest(RelFileNodeBackend rnode, ForkNumber forknum,
+					BlockNumber segno)
+{
+	BgWriterRequest *request;
+
+	if (!IsUnderPostmaster)
+		return false;			/* probably shouldn't even get here */
+
+	if (am_checkpointer)
+		elog(ERROR, "ForwardFsyncRequest must not be called in bgwriter");
+
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Count all backend writes regardless of if they fit in the queue */
+	BgWriterShmem->num_backend_writes++;
+
+	/*
+	 * If the background writer isn't running or the request queue is full,
+	 * the backend will have to perform its own fsync request.	But before
+	 * forcing that to happen, we can try to compact the background writer
+	 * request queue.
+	 */
+	if (BgWriterShmem->checkpointer_pid == 0 ||
+		(BgWriterShmem->num_requests >= BgWriterShmem->max_requests
+		 && !CompactCheckpointerRequestQueue()))
+	{
+		/*
+		 * Count the subset of writes where backends have to do their own
+		 * fsync
+		 */
+		BgWriterShmem->num_backend_fsync++;
+		LWLockRelease(BgWriterCommLock);
+		return false;
+	}
+	request = &BgWriterShmem->requests[BgWriterShmem->num_requests++];
+	request->rnode = rnode;
+	request->forknum = forknum;
+	request->segno = segno;
+	LWLockRelease(BgWriterCommLock);
+	return true;
+}
+
+/*
+ * CompactCheckpointerRequestQueue
+ *		Remove duplicates from the request queue to avoid backend fsyncs.
+ *
+ * Although a full fsync request queue is not common, it can lead to severe
+ * performance problems when it does happen.  So far, this situation has
+ * only been observed to occur when the system is under heavy write load,
+ * and especially during the "sync" phase of a checkpoint.	Without this
+ * logic, each backend begins doing an fsync for every block written, which
+ * gets very expensive and can slow down the whole system.
+ *
+ * Trying to do this every time the queue is full could lose if there
+ * aren't any removable entries.  But should be vanishingly rare in
+ * practice: there's one queue entry per shared buffer.
+ */
+static bool
+CompactCheckpointerRequestQueue()
+{
+	struct BgWriterSlotMapping
+	{
+		BgWriterRequest request;
+		int			slot;
+	};
+
+	int			n,
+				preserve_count;
+	int			num_skipped = 0;
+	HASHCTL		ctl;
+	HTAB	   *htab;
+	bool	   *skip_slot;
+
+	/* must hold BgWriterCommLock in exclusive mode */
+	Assert(LWLockHeldByMe(BgWriterCommLock));
+
+	/* Initialize temporary hash table */
+	MemSet(&ctl, 0, sizeof(ctl));
+	ctl.keysize = sizeof(BgWriterRequest);
+	ctl.entrysize = sizeof(struct BgWriterSlotMapping);
+	ctl.hash = tag_hash;
+	htab = hash_create("CompactBgwriterRequestQueue",
+					   BgWriterShmem->num_requests,
+					   &ctl,
+					   HASH_ELEM | HASH_FUNCTION);
+
+	/* Initialize skip_slot array */
+	skip_slot = palloc0(sizeof(bool) * BgWriterShmem->num_requests);
+
+	/*
+	 * The basic idea here is that a request can be skipped if it's followed
+	 * by a later, identical request.  It might seem more sensible to work
+	 * backwards from the end of the queue and check whether a request is
+	 * *preceded* by an earlier, identical request, in the hopes of doing less
+	 * copying.  But that might change the semantics, if there's an
+	 * intervening FORGET_RELATION_FSYNC or FORGET_DATABASE_FSYNC request, so
+	 * we do it this way.  It would be possible to be even smarter if we made
+	 * the code below understand the specific semantics of such requests (it
+	 * could blow away preceding entries that would end up being canceled
+	 * anyhow), but it's not clear that the extra complexity would buy us
+	 * anything.
+	 */
+	for (n = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		BgWriterRequest *request;
+		struct BgWriterSlotMapping *slotmap;
+		bool		found;
+
+		request = &BgWriterShmem->requests[n];
+		slotmap = hash_search(htab, request, HASH_ENTER, &found);
+		if (found)
+		{
+			skip_slot[slotmap->slot] = true;
+			++num_skipped;
+		}
+		slotmap->slot = n;
+	}
+
+	/* Done with the hash table. */
+	hash_destroy(htab);
+
+	/* If no duplicates, we're out of luck. */
+	if (!num_skipped)
+	{
+		pfree(skip_slot);
+		return false;
+	}
+
+	/* We found some duplicates; remove them. */
+	for (n = 0, preserve_count = 0; n < BgWriterShmem->num_requests; ++n)
+	{
+		if (skip_slot[n])
+			continue;
+		BgWriterShmem->requests[preserve_count++] = BgWriterShmem->requests[n];
+	}
+	ereport(DEBUG1,
+	   (errmsg("compacted fsync request queue from %d entries to %d entries",
+			   BgWriterShmem->num_requests, preserve_count)));
+	BgWriterShmem->num_requests = preserve_count;
+
+	/* Cleanup. */
+	pfree(skip_slot);
+	return true;
+}
+
+/*
+ * AbsorbFsyncRequests
+ *		Retrieve queued fsync requests and pass them to local smgr.
+ *
+ * This is exported because it must be called during CreateCheckPoint;
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
+ * non-checkpointer processes, do nothing if not checkpointer.
+ */
+void
+AbsorbFsyncRequests(void)
+{
+	BgWriterRequest *requests = NULL;
+	BgWriterRequest *request;
+	int			n;
+
+	if (!am_checkpointer)
+		return;
+
+	/*
+	 * We have to PANIC if we fail to absorb all the pending requests (eg,
+	 * because our hashtable runs out of memory).  This is because the system
+	 * cannot run safely if we are unable to fsync what we have been told to
+	 * fsync.  Fortunately, the hashtable is so small that the problem is
+	 * quite unlikely to arise in practice.
+	 */
+	START_CRIT_SECTION();
+
+	/*
+	 * We try to avoid holding the lock for a long time by copying the request
+	 * array.
+	 */
+	LWLockAcquire(BgWriterCommLock, LW_EXCLUSIVE);
+
+	/* Transfer write count into pending pgstats message */
+	BgWriterStats.m_buf_written_backend += BgWriterShmem->num_backend_writes;
+	BgWriterStats.m_buf_fsync_backend += BgWriterShmem->num_backend_fsync;
+
+	BgWriterShmem->num_backend_writes = 0;
+	BgWriterShmem->num_backend_fsync = 0;
+
+	n = BgWriterShmem->num_requests;
+	if (n > 0)
+	{
+		requests = (BgWriterRequest *) palloc(n * sizeof(BgWriterRequest));
+		memcpy(requests, BgWriterShmem->requests, n * sizeof(BgWriterRequest));
+	}
+	BgWriterShmem->num_requests = 0;
+
+	LWLockRelease(BgWriterCommLock);
+
+	for (request = requests; n > 0; request++, n--)
+		RememberFsyncRequest(request->rnode, request->forknum, request->segno);
+
+	if (requests)
+		pfree(requests);
+
+	END_CRIT_SECTION();
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 0a84d97..d057942 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -206,6 +206,7 @@ bool		restart_after_crash = true;
 /* PIDs of special child processes; 0 when not running */
 static pid_t StartupPID = 0,
 			BgWriterPID = 0,
+			CheckpointerPID = 0,
 			WalWriterPID = 0,
 			WalReceiverPID = 0,
 			AutoVacPID = 0,
@@ -277,7 +278,7 @@ typedef enum
 	PM_WAIT_BACKUP,				/* waiting for online backup mode to end */
 	PM_WAIT_READONLY,			/* waiting for read only backends to exit */
 	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
-	PM_SHUTDOWN,				/* waiting for bgwriter to do shutdown ckpt */
+	PM_SHUTDOWN,				/* waiting for checkpointer to do shutdown ckpt */
 	PM_SHUTDOWN_2,				/* waiting for archiver and walsenders to
 								 * finish */
 	PM_WAIT_DEAD_END,			/* waiting for dead_end children to exit */
@@ -463,6 +464,7 @@ static void ShmemBackendArrayRemove(Backend *bn);
 
 #define StartupDataBase()		StartChildProcess(StartupProcess)
 #define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
+#define StartCheckpointer()		StartChildProcess(CheckpointerProcess)
 #define StartWalWriter()		StartChildProcess(WalWriterProcess)
 #define StartWalReceiver()		StartChildProcess(WalReceiverProcess)
 
@@ -1015,8 +1017,8 @@ PostmasterMain(int argc, char *argv[])
 	 * CAUTION: when changing this list, check for side-effects on the signal
 	 * handling setup of child processes.  See tcop/postgres.c,
 	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
-	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c, and
-	 * postmaster/syslogger.c.
+	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
+	 * postmaster/syslogger.c and postmaster/checkpointer.c
 	 */
 	pqinitmask();
 	PG_SETMASK(&BlockSig);
@@ -1353,10 +1355,14 @@ ServerLoop(void)
 		 * state that prevents it, start one.  It doesn't matter if this
 		 * fails, we'll just try again later.
 		 */
-		if (BgWriterPID == 0 &&
-			(pmState == PM_RUN || pmState == PM_RECOVERY ||
-			 pmState == PM_HOT_STANDBY))
-			BgWriterPID = StartBackgroundWriter();
+		if (pmState == PM_RUN || pmState == PM_RECOVERY ||
+			 pmState == PM_HOT_STANDBY)
+		{
+			if (BgWriterPID == 0)
+				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
+		}
 
 		/*
 		 * Likewise, if we have lost the walwriter process, try to start a new
@@ -2034,6 +2040,8 @@ SIGHUP_handler(SIGNAL_ARGS)
 			signal_child(StartupPID, SIGHUP);
 		if (BgWriterPID != 0)
 			signal_child(BgWriterPID, SIGHUP);
+		if (CheckpointerPID != 0)
+			signal_child(CheckpointerPID, SIGHUP);
 		if (WalWriterPID != 0)
 			signal_child(WalWriterPID, SIGHUP);
 		if (WalReceiverPID != 0)
@@ -2106,6 +2114,8 @@ pmdie(SIGNAL_ARGS)
 				/* and the walwriter too */
 				if (WalWriterPID != 0)
 					signal_child(WalWriterPID, SIGTERM);
+				if (BgWriterPID != 0)
+					signal_child(BgWriterPID, SIGTERM);
 
 				/*
 				 * If we're in recovery, we can't kill the startup process
@@ -2146,9 +2156,11 @@ pmdie(SIGNAL_ARGS)
 				signal_child(StartupPID, SIGTERM);
 			if (WalReceiverPID != 0)
 				signal_child(WalReceiverPID, SIGTERM);
+			if (BgWriterPID != 0)
+				signal_child(BgWriterPID, SIGTERM);
 			if (pmState == PM_RECOVERY)
 			{
-				/* only bgwriter is active in this state */
+				/* only checkpointer is active in this state */
 				pmState = PM_WAIT_BACKENDS;
 			}
 			else if (pmState == PM_RUN ||
@@ -2193,6 +2205,8 @@ pmdie(SIGNAL_ARGS)
 				signal_child(StartupPID, SIGQUIT);
 			if (BgWriterPID != 0)
 				signal_child(BgWriterPID, SIGQUIT);
+			if (CheckpointerPID != 0)
+				signal_child(CheckpointerPID, SIGQUIT);
 			if (WalWriterPID != 0)
 				signal_child(WalWriterPID, SIGQUIT);
 			if (WalReceiverPID != 0)
@@ -2323,12 +2337,14 @@ reaper(SIGNAL_ARGS)
 			}
 
 			/*
-			 * Crank up the background writer, if we didn't do that already
+			 * Crank up background tasks, if we didn't do that already
 			 * when we entered consistent recovery state.  It doesn't matter
 			 * if this fails, we'll just try again later.
 			 */
 			if (BgWriterPID == 0)
 				BgWriterPID = StartBackgroundWriter();
+			if (CheckpointerPID == 0)
+				CheckpointerPID = StartCheckpointer();
 
 			/*
 			 * Likewise, start other special children as needed.  In a restart
@@ -2356,10 +2372,22 @@ reaper(SIGNAL_ARGS)
 		if (pid == BgWriterPID)
 		{
 			BgWriterPID = 0;
+			if (!EXIT_STATUS_0(exitstatus))
+				HandleChildCrash(pid, exitstatus,
+								 _("background writer process"));
+			continue;
+		}
+
+		/*
+		 * Was it the checkpointer?
+		 */
+		if (pid == CheckpointerPID)
+		{
+			CheckpointerPID = 0;
 			if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
 			{
 				/*
-				 * OK, we saw normal exit of the bgwriter after it's been told
+				 * OK, we saw normal exit of the checkpointer after it's been told
 				 * to shut down.  We expect that it wrote a shutdown
 				 * checkpoint.	(If for some reason it didn't, recovery will
 				 * occur on next postmaster start.)
@@ -2396,11 +2424,11 @@ reaper(SIGNAL_ARGS)
 			else
 			{
 				/*
-				 * Any unexpected exit of the bgwriter (including FATAL exit)
+				 * Any unexpected exit of the checkpointer (including FATAL exit)
 				 * is treated as a crash.
 				 */
 				HandleChildCrash(pid, exitstatus,
-								 _("background writer process"));
+								 _("checkpointer process"));
 			}
 
 			continue;
@@ -2584,8 +2612,8 @@ CleanupBackend(int pid,
 }
 
 /*
- * HandleChildCrash -- cleanup after failed backend, bgwriter, walwriter,
- * or autovacuum.
+ * HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
+ * walwriter or autovacuum.
  *
  * The objectives here are to clean up our local state about the child
  * process, and to signal all other remaining children to quickdie.
@@ -2678,6 +2706,18 @@ HandleChildCrash(int pid, int exitstatus, const char *procname)
 		signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
 	}
 
+	/* Take care of the checkpointer too */
+	if (pid == CheckpointerPID)
+		CheckpointerPID = 0;
+	else if (CheckpointerPID != 0 && !FatalError)
+	{
+		ereport(DEBUG2,
+				(errmsg_internal("sending %s to process %d",
+								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
+								 (int) CheckpointerPID)));
+		signal_child(CheckpointerPID, (SendStop ? SIGSTOP : SIGQUIT));
+	}
+
 	/* Take care of the walwriter too */
 	if (pid == WalWriterPID)
 		WalWriterPID = 0;
@@ -2857,9 +2897,10 @@ PostmasterStateMachine(void)
 	{
 		/*
 		 * PM_WAIT_BACKENDS state ends when we have no regular backends
-		 * (including autovac workers) and no walwriter or autovac launcher.
-		 * If we are doing crash recovery then we expect the bgwriter to exit
-		 * too, otherwise not.	The archiver, stats, and syslogger processes
+		 * (including autovac workers) and no walwriter, autovac launcher
+		 * or bgwriter.  If we are doing crash recovery then we expect the
+		 * checkpointer to exit as well, otherwise not.
+		 * The archiver, stats, and syslogger processes
 		 * are disregarded since they are not connected to shared memory; we
 		 * also disregard dead_end children here. Walsenders are also
 		 * disregarded, they will be terminated later after writing the
@@ -2868,7 +2909,8 @@ PostmasterStateMachine(void)
 		if (CountChildren(BACKEND_TYPE_NORMAL | BACKEND_TYPE_AUTOVAC) == 0 &&
 			StartupPID == 0 &&
 			WalReceiverPID == 0 &&
-			(BgWriterPID == 0 || !FatalError) &&
+			BgWriterPID == 0 &&
+			(CheckpointerPID == 0 || !FatalError) &&
 			WalWriterPID == 0 &&
 			AutoVacPID == 0)
 		{
@@ -2890,22 +2932,22 @@ PostmasterStateMachine(void)
 				/*
 				 * If we get here, we are proceeding with normal shutdown. All
 				 * the regular children are gone, and it's time to tell the
-				 * bgwriter to do a shutdown checkpoint.
+				 * checkpointer to do a shutdown checkpoint.
 				 */
 				Assert(Shutdown > NoShutdown);
-				/* Start the bgwriter if not running */
-				if (BgWriterPID == 0)
-					BgWriterPID = StartBackgroundWriter();
+				/* Start the checkpointer if not running */
+				if (CheckpointerPID == 0)
+					CheckpointerPID = StartCheckpointer();
 				/* And tell it to shut down */
-				if (BgWriterPID != 0)
+				if (CheckpointerPID != 0)
 				{
-					signal_child(BgWriterPID, SIGUSR2);
+					signal_child(CheckpointerPID, SIGUSR2);
 					pmState = PM_SHUTDOWN;
 				}
 				else
 				{
 					/*
-					 * If we failed to fork a bgwriter, just shut down. Any
+					 * If we failed to fork a checkpointer, just shut down. Any
 					 * required cleanup will happen at next restart. We set
 					 * FatalError so that an "abnormal shutdown" message gets
 					 * logged when we exit.
@@ -2964,6 +3006,7 @@ PostmasterStateMachine(void)
 			Assert(StartupPID == 0);
 			Assert(WalReceiverPID == 0);
 			Assert(BgWriterPID == 0);
+			Assert(CheckpointerPID == 0);
 			Assert(WalWriterPID == 0);
 			Assert(AutoVacPID == 0);
 			/* syslogger is not considered here */
@@ -4143,6 +4186,8 @@ sigusr1_handler(SIGNAL_ARGS)
 		 */
 		Assert(BgWriterPID == 0);
 		BgWriterPID = StartBackgroundWriter();
+		Assert(CheckpointerPID == 0);
+		CheckpointerPID = StartCheckpointer();
 
 		pmState = PM_RECOVERY;
 	}
@@ -4429,6 +4474,10 @@ StartChildProcess(AuxProcType type)
 				ereport(LOG,
 				   (errmsg("could not fork background writer process: %m")));
 				break;
+			case CheckpointerProcess:
+				ereport(LOG,
+				   (errmsg("could not fork checkpointer process: %m")));
+				break;
 			case WalWriterProcess:
 				ereport(LOG,
 						(errmsg("could not fork WAL writer process: %m")));
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8647edd..184e820 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -1278,11 +1278,9 @@ BufferSync(int flags)
 					break;
 
 				/*
-				 * Perform normal bgwriter duties and sleep to throttle our
-				 * I/O rate.
+				 * Sleep to throttle our I/O rate.
 				 */
-				CheckpointWriteDelay(flags,
-									 (double) num_written / num_to_write);
+				CheckpointWriteDelay(flags, (double) num_written / num_to_write);
 			}
 		}
 
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 3015885..a761369 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -38,7 +38,7 @@
 /*
  * Special values for the segno arg to RememberFsyncRequest.
  *
- * Note that CompactBgwriterRequestQueue assumes that it's OK to remove an
+ * Note that CompactcheckpointerRequestQueue assumes that it's OK to remove an
  * fsync request from the queue if an identical, subsequent request is found.
  * See comments there before making changes here.
  */
@@ -77,7 +77,7 @@
  *	Inactive segments are those that once contained data but are currently
  *	not needed because of an mdtruncate() operation.  The reason for leaving
  *	them present at size zero, rather than unlinking them, is that other
- *	backends and/or the bgwriter might be holding open file references to
+ *	backends and/or the checkpointer might be holding open file references to
  *	such segments.	If the relation expands again after mdtruncate(), such
  *	that a deactivated segment becomes active again, it is important that
  *	such file references still be valid --- else data might get written
@@ -111,7 +111,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
 
 
 /*
- * In some contexts (currently, standalone backends and the bgwriter process)
+ * In some contexts (currently, standalone backends and the checkpointer process)
  * we keep track of pending fsync operations: we need to remember all relation
  * segments that have been written since the last checkpoint, so that we can
  * fsync them down to disk before completing the next checkpoint.  This hash
@@ -123,7 +123,7 @@ static MemoryContext MdCxt;		/* context for all md.c allocations */
  * a hash table, because we don't expect there to be any duplicate requests.
  *
  * (Regular backends do not track pending operations locally, but forward
- * them to the bgwriter.)
+ * them to the checkpointer.)
  */
 typedef struct
 {
@@ -194,7 +194,7 @@ mdinit(void)
 	 * Create pending-operations hashtable if we need it.  Currently, we need
 	 * it if we are standalone (not under a postmaster) OR if we are a
 	 * bootstrap-mode subprocess of a postmaster (that is, a startup or
-	 * bgwriter process).
+	 * checkpointer process).
 	 */
 	if (!IsUnderPostmaster || IsBootstrapProcessingMode())
 	{
@@ -214,10 +214,10 @@ mdinit(void)
 }
 
 /*
- * In archive recovery, we rely on bgwriter to do fsyncs, but we will have
+ * In archive recovery, we rely on checkpointer to do fsyncs, but we will have
  * already created the pendingOpsTable during initialization of the startup
  * process.  Calling this function drops the local pendingOpsTable so that
- * subsequent requests will be forwarded to bgwriter.
+ * subsequent requests will be forwarded to checkpointer.
  */
 void
 SetForwardFsyncRequests(void)
@@ -765,9 +765,9 @@ mdnblocks(SMgrRelation reln, ForkNumber forknum)
 	 * NOTE: this assumption could only be wrong if another backend has
 	 * truncated the relation.	We rely on higher code levels to handle that
 	 * scenario by closing and re-opening the md fd, which is handled via
-	 * relcache flush.	(Since the bgwriter doesn't participate in relcache
+	 * relcache flush.	(Since the checkpointer doesn't participate in relcache
 	 * flush, it could have segment chain entries for inactive segments;
-	 * that's OK because the bgwriter never needs to compute relation size.)
+	 * that's OK because the checkpointer never needs to compute relation size.)
 	 */
 	while (v->mdfd_chain != NULL)
 	{
@@ -957,7 +957,7 @@ mdsync(void)
 		elog(ERROR, "cannot sync without a pendingOpsTable");
 
 	/*
-	 * If we are in the bgwriter, the sync had better include all fsync
+	 * If we are in the checkpointer, the sync had better include all fsync
 	 * requests that were queued by backends up to this point.	The tightest
 	 * race condition that could occur is that a buffer that must be written
 	 * and fsync'd for the checkpoint could have been dumped by a backend just
@@ -1033,7 +1033,7 @@ mdsync(void)
 			int			failures;
 
 			/*
-			 * If in bgwriter, we want to absorb pending requests every so
+			 * If in checkpointer, we want to absorb pending requests every so
 			 * often to prevent overflow of the fsync request queue.  It is
 			 * unspecified whether newly-added entries will be visited by
 			 * hash_seq_search, but we don't care since we don't need to
@@ -1070,9 +1070,9 @@ mdsync(void)
 				 * say "but an unreferenced SMgrRelation is still a leak!" Not
 				 * really, because the only case in which a checkpoint is done
 				 * by a process that isn't about to shut down is in the
-				 * bgwriter, and it will periodically do smgrcloseall(). This
+				 * checkpointer, and it will periodically do smgrcloseall(). This
 				 * fact justifies our not closing the reln in the success path
-				 * either, which is a good thing since in non-bgwriter cases
+				 * either, which is a good thing since in non-checkpointer cases
 				 * we couldn't safely do that.)  Furthermore, in many cases
 				 * the relation will have been dirtied through this same smgr
 				 * relation, and so we can save a file open/close cycle.
@@ -1301,7 +1301,7 @@ register_unlink(RelFileNodeBackend rnode)
 	else
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the request
+		 * Notify the checkpointer about it.  If we fail to queue the request
 		 * message, we have to sleep and try again, because we can't simply
 		 * delete the file now.  Ugly, but hopefully won't happen often.
 		 *
@@ -1315,10 +1315,10 @@ register_unlink(RelFileNodeBackend rnode)
 }
 
 /*
- * RememberFsyncRequest() -- callback from bgwriter side of fsync request
+ * RememberFsyncRequest() -- callback from checkpointer side of fsync request
  *
  * We stuff most fsync requests into the local hash table for execution
- * during the bgwriter's next checkpoint.  UNLINK requests go into a
+ * during the checkpointer's next checkpoint.  UNLINK requests go into a
  * separate linked list, however, because they get processed separately.
  *
  * The range of possible segment numbers is way less than the range of
@@ -1460,20 +1460,20 @@ ForgetRelationFsyncRequests(RelFileNodeBackend rnode, ForkNumber forknum)
 	else if (IsUnderPostmaster)
 	{
 		/*
-		 * Notify the bgwriter about it.  If we fail to queue the revoke
+		 * Notify the checkpointer about it.  If we fail to queue the revoke
 		 * message, we have to sleep and try again ... ugly, but hopefully
 		 * won't happen often.
 		 *
 		 * XXX should we CHECK_FOR_INTERRUPTS in this loop?  Escaping with an
 		 * error would leave the no-longer-used file still present on disk,
-		 * which would be bad, so I'm inclined to assume that the bgwriter
+		 * which would be bad, so I'm inclined to assume that the checkpointer
 		 * will always empty the queue soon.
 		 */
 		while (!ForwardFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC))
 			pg_usleep(10000L);	/* 10 msec seems a good number */
 
 		/*
-		 * Note we don't wait for the bgwriter to actually absorb the revoke
+		 * Note we don't wait for the checkpointer to actually absorb the revoke
 		 * message; see mdsync() for the implications.
 		 */
 	}
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 4eaa243..cb43879 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -256,7 +256,7 @@ typedef struct RmgrData
 extern const RmgrData RmgrTable[];
 
 /*
- * Exported to support xlog switching from bgwriter
+ * Exported to support xlog switching from checkpointer
  */
 extern pg_time_t GetLastSegSwitchTime(void);
 extern XLogRecPtr RequestXLogSwitch(void);
diff --git a/src/include/bootstrap/bootstrap.h b/src/include/bootstrap/bootstrap.h
index cee9bd1..6153b7a 100644
--- a/src/include/bootstrap/bootstrap.h
+++ b/src/include/bootstrap/bootstrap.h
@@ -22,6 +22,7 @@ typedef enum
 	BootstrapProcess,
 	StartupProcess,
 	BgWriterProcess,
+	CheckpointerProcess,
 	WalWriterProcess,
 	WalReceiverProcess,
 
diff --git a/src/include/postmaster/bgwriter.h b/src/include/postmaster/bgwriter.h
index eaf2206..c05901e 100644
--- a/src/include/postmaster/bgwriter.h
+++ b/src/include/postmaster/bgwriter.h
@@ -23,6 +23,7 @@ extern int	CheckPointWarning;
 extern double CheckPointCompletionTarget;
 
 extern void BackgroundWriterMain(void);
+extern void CheckpointerMain(void);
 
 extern void RequestCheckpoint(int flags);
 extern void CheckpointWriteDelay(int flags, double progress);
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 46ec625..6e798b1 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -190,11 +190,11 @@ extern PROC_HDR *ProcGlobal;
  * We set aside some extra PGPROC structures for auxiliary processes,
  * ie things that aren't full-fledged backends but need shmem access.
  *
- * Background writer and WAL writer run during normal operation. Startup
- * process and WAL receiver also consume 2 slots, but WAL writer is
- * launched only after startup has exited, so we only need 3 slots.
+ * Background writer, checkpointer and WAL writer run during normal operation.
+ * Startup process and WAL receiver also consume 2 slots, but WAL writer is
+ * launched only after startup has exited, so we only need 4 slots.
  */
-#define NUM_AUXILIARY_PROCS		3
+#define NUM_AUXILIARY_PROCS		4
 
 
 /* configurable options */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index 2a27e0b..d5afe01 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -19,7 +19,7 @@
 
 /*
  * Reasons for signalling a Postgres child process (a backend or an auxiliary
- * process, like bgwriter).  We can cope with concurrent signals for different
+ * process, like checkpointer).  We can cope with concurrent signals for different
  * reasons.  However, if the same reason is signaled multiple times in quick
  * succession, the process is likely to observe only one notification of it.
  * This is okay for the present uses.