Clog handling on exec'ed backend

Bruce Momjian <pgman@candle.pha.pa.us> writes:

It basically makes one of the Clog data structures into a shared memory
area when using exec (EXEC_BACKEND is defined). It passes all the
regression/initdb tests on Unix.

It would be cleaner to make the array of LWLockIds part of ClogCtlData,
if you're going to do it that way. I have doubts that pushing all
LWLockIds into shared memory is a feasible solution, however.

Out of curiosity: have you actually tested any of this Windows code
you're proposing to commit? A lot of it looks to me like it's not
gonna work --- stuff is getting done too soon or too late. For
example, I don't see how a backend is going to read GUC variables
when it doesn't yet know where the data directory is.

regards, tom lane

Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

It basically makes one of the Clog data structures into a shared memory
area when using exec (EXEC_BACKEND is defined). It passes all the
regression/initdb tests on Unix.

It would be cleaner to make the array of LWLockIds part of ClogCtlData,
if you're going to do it that way. I have doubts that pushing all
LWLockIds into shared memory is a feasible solution, however.

OK, we will keep it as proposed so that shared memory issue only effects
exec() setups.

Out of curiosity: have you actually tested any of this Windows code
you're proposing to commit? A lot of it looks to me like it's not
gonna work --- stuff is getting done too soon or too late. For
example, I don't see how a backend is going to read GUC variables
when it doesn't yet know where the data directory is.

I have not tested it yet because it _all_ has to be done before anything
is going to work. That's why I am trying exec() on Unix first as at
least a minimal way to test things. I am going to have to move things
around once I have the code working.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Committed --- I need to make more changes in this area in my next patch.

---------------------------------------------------------------------------

Bruce Momjian wrote:

Here is a another patch on the way to exec'ed Unix and Win32.

It basically makes one of the Clog data structures into a shared memory
area when using exec (EXEC_BACKEND is defined). It passes all the
regression/initdb tests on Unix.

-- 
Bruce Momjian                        |  http://candle.pha.pa.us
pgman@candle.pha.pa.us               |  (610) 359-1001
+  If your life is a hard drive,     |  13 Roberts Road
+  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Index: src/backend/access/transam/clog.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/access/transam/clog.c,v
retrieving revision 1.14
diff -c -c -r1.14 clog.c
*** src/backend/access/transam/clog.c	2 May 2003 21:59:31 -0000	1.14
--- src/backend/access/transam/clog.c	2 May 2003 22:09:26 -0000
***************
*** 157,163 ****
* The value is automatically inherited by backends via fork, and
* doesn't need to be in shared memory.
*/
! static LWLockId ClogBufferLocks[NUM_CLOG_BUFFERS];		/* Per-buffer I/O locks */

/*
* ClogDir is set during CLOGShmemInit and does not change thereafter.
--- 157,163 ----
* The value is automatically inherited by backends via fork, and
* doesn't need to be in shared memory.
*/
! static LWLockId *ClogBufferLocks;		/* Per-buffer I/O locks */

/*
* ClogDir is set during CLOGShmemInit and does not change thereafter.
***************
*** 271,311 ****
/*
* Initialization of shared memory for CLOG
*/
-
int
CLOGShmemSize(void)
{
! return MAXALIGN(sizeof(ClogCtlData) + CLOG_BLCKSZ * NUM_CLOG_BUFFERS);
}

void
CLOGShmemInit(void)
{
bool found;
- char *bufptr;
int slotno;

/* this must agree with space requested by CLOGShmemSize() */
! ClogCtl = (ClogCtlData *)
! ShmemInitStruct("CLOG Ctl",
! MAXALIGN(sizeof(ClogCtlData) +
! CLOG_BLCKSZ * NUM_CLOG_BUFFERS),
! &found);
! Assert(!found);

! memset(ClogCtl, 0, sizeof(ClogCtlData));

! bufptr = ((char *) ClogCtl) + sizeof(ClogCtlData);

! for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++)
! {
! ClogCtl->page_buffer[slotno] = bufptr;
! ClogCtl->page_status[slotno] = CLOG_PAGE_EMPTY;
! ClogBufferLocks[slotno] = LWLockAssign();
! bufptr += CLOG_BLCKSZ;
}

! /* ClogCtl->latest_page_number will be set later */

/* Init CLOG directory path */
snprintf(ClogDir, MAXPGPATH, "%s/pg_clog", DataDir);
--- 271,337 ----
/*
* Initialization of shared memory for CLOG
*/
int
CLOGShmemSize(void)
{
! 	return MAXALIGN(sizeof(ClogCtlData) + CLOG_BLCKSZ * NUM_CLOG_BUFFERS)
! #ifdef EXEC_BACKEND
! 			+ MAXALIGN(NUM_CLOG_BUFFERS * sizeof(LWLockId))
! #endif
! 	;
}

+
void
CLOGShmemInit(void)
{
bool found;
int slotno;

+ /* Handle ClogCtl */
+
/* this must agree with space requested by CLOGShmemSize() */
! ClogCtl = (ClogCtlData *) ShmemInitStruct("CLOG Ctl",
! MAXALIGN(sizeof(ClogCtlData) +
! CLOG_BLCKSZ * NUM_CLOG_BUFFERS), &found);
!
! if (!IsUnderPostmaster)
! /* Initialize ClogCtl shared memory area */
! {
! char *bufptr;

! Assert(!found);

! memset(ClogCtl, 0, sizeof(ClogCtlData));

! bufptr = (char *)ClogCtl + sizeof(ClogCtlData);
!
! for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++)
! {
! ClogCtl->page_buffer[slotno] = bufptr;
! ClogCtl->page_status[slotno] = CLOG_PAGE_EMPTY;
! bufptr += CLOG_BLCKSZ;
! }
!
! /* ClogCtl->latest_page_number will be set later */
}
+ else
+ Assert(found);

! /* Handle ClogBufferLocks */
!
! #ifdef EXEC_BACKEND
! ClogBufferLocks = (LWLockId *) ShmemInitStruct("CLOG Buffer Locks",
! NUM_CLOG_BUFFERS * sizeof(LWLockId), &found);
! Assert((!found && !IsUnderPostmaster) || (found && IsUnderPostmaster));
! #else
! ClogBufferLocks = malloc(NUM_CLOG_BUFFERS * sizeof(LWLockId));
! Assert(ClogBufferLocks);
! #endif
!
! if (!IsUnderPostmaster)
! for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++)
! ClogBufferLocks[slotno] = LWLockAssign();

/* Init CLOG directory path */
snprintf(ClogDir, MAXPGPATH, "%s/pg_clog", DataDir);
Index: src/backend/bootstrap/bootstrap.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/bootstrap/bootstrap.c,v
retrieving revision 1.150
diff -c -c -r1.150 bootstrap.c
*** src/backend/bootstrap/bootstrap.c	2 May 2003 21:59:31 -0000	1.150
--- src/backend/bootstrap/bootstrap.c	2 May 2003 22:09:28 -0000
***************
*** 301,306 ****
--- 301,311 ----

Assert(dbName);

+ 	if (IsUnderPostmaster && ExecBackend && MyProc /* ordinary backend */)
+ 	{
+ 		AttachSharedMemoryAndSemaphores();
+ 	}
+ 	
if (!IsUnderPostmaster)
{
if (!potential_DataDir)
Index: src/backend/postmaster/postmaster.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/postmaster/postmaster.c,v
retrieving revision 1.319
diff -c -c -r1.319 postmaster.c
*** src/backend/postmaster/postmaster.c	2 May 2003 22:02:47 -0000	1.319
--- src/backend/postmaster/postmaster.c	2 May 2003 22:09:30 -0000
***************
*** 172,177 ****
--- 172,184 ----
static int	ServerSock_UNIX = INVALID_SOCK;		/* stream socket server */
#endif

+ /* Used to reduce macros tests */
+ #ifdef EXEC_BACKEND
+ const bool ExecBackend = true;
+ #else
+ const bool ExecBackend = false;
+ #endif
+
/*
* Set by the -o option
*/
***************
*** 1407,1413 ****
elog(DEBUG1, "processCancelRequest: CheckPointPID in cancel request for process %d", backendPID);
return;
}
!
/* See if we have a matching backend */

for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
--- 1414,1424 ----
elog(DEBUG1, "processCancelRequest: CheckPointPID in cancel request for process %d", backendPID);
return;
}
! 	else if (ExecBackend)
! 	{
! 		AttachSharedMemoryAndSemaphores();
! 	}
! 	
/* See if we have a matching backend */

for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
Index: src/backend/storage/ipc/ipci.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/storage/ipc/ipci.c,v
retrieving revision 1.51
diff -c -c -r1.51 ipci.c
*** src/backend/storage/ipc/ipci.c	2 May 2003 21:59:31 -0000	1.51
--- src/backend/storage/ipc/ipci.c	2 May 2003 22:09:30 -0000
***************
*** 134,136 ****
--- 134,149 ----
*/
PMSignalInit();
}
+ 
+ 
+ /*
+  * AttachSharedMemoryAndSemaphores
+  *		Attaches to the existing shared resources when exec()'d off
+  *		by the postmaster.
+  */
+ void
+ AttachSharedMemoryAndSemaphores(void)
+ {
+ 	CLOGShmemInit();
+ }
+ 
Index: src/backend/tcop/postgres.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/tcop/postgres.c,v
retrieving revision 1.329
diff -c -c -r1.329 postgres.c
*** src/backend/tcop/postgres.c	2 May 2003 21:59:31 -0000	1.329
--- src/backend/tcop/postgres.c	2 May 2003 22:09:32 -0000
***************
*** 1453,1458 ****
--- 1453,1459 ----
break;
}

+ 
/*
* -d is not the same as setting
* log_min_messages because it enables other
***************
*** 1577,1582 ****
--- 1578,1586 ----
* restart... */
}
BaseInit();
+ #ifdef EXECBACKEND
+ 		AttachSharedMemoryAndSemaphores();
+ #endif
}
else
{
Index: src/include/miscadmin.h
===================================================================
RCS file: /cvsroot/pgsql-server/src/include/miscadmin.h,v
retrieving revision 1.120
diff -c -c -r1.120 miscadmin.h
*** src/include/miscadmin.h	2 May 2003 21:59:31 -0000	1.120
--- src/include/miscadmin.h	2 May 2003 22:09:33 -0000
***************
*** 106,111 ****
--- 106,112 ----
*/
extern bool IsUnderPostmaster;
extern bool ClientAuthInProgress;
+ extern const bool ExecBackend;

extern int	PostmasterMain(int argc, char *argv[]);
extern void ClosePostmasterPorts(bool pgstat_too);
Index: src/include/storage/ipc.h
===================================================================
RCS file: /cvsroot/pgsql-server/src/include/storage/ipc.h,v
retrieving revision 1.59
diff -c -c -r1.59 ipc.h
*** src/include/storage/ipc.h	2 May 2003 21:59:31 -0000	1.59
--- src/include/storage/ipc.h	2 May 2003 22:09:33 -0000
***************
*** 32,36 ****
--- 32,37 ----
extern void CreateSharedMemoryAndSemaphores(bool makePrivate,
int maxBackends,
int port);
+ extern void AttachSharedMemoryAndSemaphores(void);

#endif /* IPC_H */

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-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073