Patch: add timing of buffer I/O requests

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..45b601c 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -35,6 +35,7 @@ SUBDIRS = \
 		pg_standby	\
 		pg_stat_statements \
 		pg_test_fsync	\
+		pg_test_timing	\
 		pg_trgm		\
 		pg_upgrade	\
 		pg_upgrade_support \
diff --git a/contrib/pg_stat_statements/Makefile b/contrib/pg_stat_statements/Makefile
index e086fd8..971773e 100644
--- a/contrib/pg_stat_statements/Makefile
+++ b/contrib/pg_stat_statements/Makefile
@@ -4,7 +4,8 @@ MODULE_big = pg_stat_statements
 OBJS = pg_stat_statements.o
 
 EXTENSION = pg_stat_statements
-DATA = pg_stat_statements--1.0.sql pg_stat_statements--unpackaged--1.0.sql
+DATA = pg_stat_statements--1.1.sql pg_stat_statements--1.0--1.1.sql \
+       pg_stat_statements--unpackaged--1.0.sql
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
new file mode 100644
index 0000000..20bd5e3
--- /dev/null
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
@@ -0,0 +1,26 @@
+/* contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.1'" to load this file. \quit
+
+CREATE OR REPLACE FUNCTION pg_stat_statements(
+    OUT userid oid,
+    OUT dbid oid,
+    OUT query text,
+    OUT calls int8,
+    OUT total_time float8,
+    OUT rows int8,
+    OUT shared_blks_hit int8,
+    OUT shared_blks_read int8,
+    OUT shared_blks_written int8,
+    OUT local_blks_hit int8,
+    OUT local_blks_read int8,
+    OUT local_blks_written int8,
+    OUT temp_blks_read int8,
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
+)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0.sql
deleted file mode 100644
index 5294a01..0000000
--- a/contrib/pg_stat_statements/pg_stat_statements--1.0.sql
+++ /dev/null
@@ -1,39 +0,0 @@
-/* contrib/pg_stat_statements/pg_stat_statements--1.0.sql */
-
--- complain if script is sourced in psql, rather than via CREATE EXTENSION
-\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
-
--- Register functions.
-CREATE FUNCTION pg_stat_statements_reset()
-RETURNS void
-AS 'MODULE_PATHNAME'
-LANGUAGE C;
-
-CREATE FUNCTION pg_stat_statements(
-    OUT userid oid,
-    OUT dbid oid,
-    OUT query text,
-    OUT calls int8,
-    OUT total_time float8,
-    OUT rows int8,
-    OUT shared_blks_hit int8,
-    OUT shared_blks_read int8,
-    OUT shared_blks_written int8,
-    OUT local_blks_hit int8,
-    OUT local_blks_read int8,
-    OUT local_blks_written int8,
-    OUT temp_blks_read int8,
-    OUT temp_blks_written int8
-)
-RETURNS SETOF record
-AS 'MODULE_PATHNAME'
-LANGUAGE C;
-
--- Register a view on the function for ease of use.
-CREATE VIEW pg_stat_statements AS
-  SELECT * FROM pg_stat_statements();
-
-GRANT SELECT ON pg_stat_statements TO PUBLIC;
-
--- Don't want this to be available to non-superusers.
-REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
new file mode 100644
index 0000000..8bd2868
--- /dev/null
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
@@ -0,0 +1,41 @@
+/* contrib/pg_stat_statements/pg_stat_statements--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
+
+-- Register functions.
+CREATE FUNCTION pg_stat_statements_reset()
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+CREATE FUNCTION pg_stat_statements(
+    OUT userid oid,
+    OUT dbid oid,
+    OUT query text,
+    OUT calls int8,
+    OUT total_time float8,
+    OUT rows int8,
+    OUT shared_blks_hit int8,
+    OUT shared_blks_read int8,
+    OUT shared_blks_written int8,
+    OUT local_blks_hit int8,
+    OUT local_blks_read int8,
+    OUT local_blks_written int8,
+    OUT temp_blks_read int8,
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
+)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+-- Register a view on the function for ease of use.
+CREATE VIEW pg_stat_statements AS
+  SELECT * FROM pg_stat_statements();
+
+GRANT SELECT ON pg_stat_statements TO PUBLIC;
+
+-- Don't want this to be available to non-superusers.
+REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 434aa71..cdcf4e8 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -83,6 +83,8 @@ typedef struct Counters
 	int64		local_blks_written;		/* # of local disk blocks written */
 	int64		temp_blks_read; /* # of temp blocks read */
 	int64		temp_blks_written;		/* # of temp blocks written */
+	double		time_read;		/* time spent reading in seconds */
+	double		time_write;		/* time spent writing in seconds */
 	double		usage;			/* usage factor */
 } Counters;
 
@@ -616,9 +618,9 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 		instr_time	start;
 		instr_time	duration;
 		uint64		rows = 0;
-		BufferUsage bufusage;
+		BufferUsage bufusage_start, bufusage;
 
-		bufusage = pgBufferUsage;
+		bufusage_start = pgBufferUsage;
 		INSTR_TIME_SET_CURRENT(start);
 
 		nested_level++;
@@ -649,21 +651,25 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 
 		/* calc differences of buffer counters. */
 		bufusage.shared_blks_hit =
-			pgBufferUsage.shared_blks_hit - bufusage.shared_blks_hit;
+			pgBufferUsage.shared_blks_hit - bufusage_start.shared_blks_hit;
 		bufusage.shared_blks_read =
-			pgBufferUsage.shared_blks_read - bufusage.shared_blks_read;
+			pgBufferUsage.shared_blks_read - bufusage_start.shared_blks_read;
 		bufusage.shared_blks_written =
-			pgBufferUsage.shared_blks_written - bufusage.shared_blks_written;
+			pgBufferUsage.shared_blks_written - bufusage_start.shared_blks_written;
 		bufusage.local_blks_hit =
-			pgBufferUsage.local_blks_hit - bufusage.local_blks_hit;
+			pgBufferUsage.local_blks_hit - bufusage_start.local_blks_hit;
 		bufusage.local_blks_read =
-			pgBufferUsage.local_blks_read - bufusage.local_blks_read;
+			pgBufferUsage.local_blks_read - bufusage_start.local_blks_read;
 		bufusage.local_blks_written =
-			pgBufferUsage.local_blks_written - bufusage.local_blks_written;
+			pgBufferUsage.local_blks_written - bufusage_start.local_blks_written;
 		bufusage.temp_blks_read =
-			pgBufferUsage.temp_blks_read - bufusage.temp_blks_read;
+			pgBufferUsage.temp_blks_read - bufusage_start.temp_blks_read;
 		bufusage.temp_blks_written =
-			pgBufferUsage.temp_blks_written - bufusage.temp_blks_written;
+			pgBufferUsage.temp_blks_written - bufusage_start.temp_blks_written;
+		bufusage.time_read = pgBufferUsage.time_read;
+		INSTR_TIME_SUBTRACT(bufusage.time_read, bufusage_start.time_read);
+		bufusage.time_write = pgBufferUsage.time_write;
+		INSTR_TIME_SUBTRACT(bufusage.time_write, bufusage_start.time_write);
 
 		pgss_store(queryString, INSTR_TIME_GET_DOUBLE(duration), rows,
 				   &bufusage);
@@ -772,6 +778,8 @@ pgss_store(const char *query, double total_time, uint64 rows,
 		e->counters.local_blks_written += bufusage->local_blks_written;
 		e->counters.temp_blks_read += bufusage->temp_blks_read;
 		e->counters.temp_blks_written += bufusage->temp_blks_written;
+		e->counters.time_read +=  INSTR_TIME_GET_DOUBLE(bufusage->time_read);
+		e->counters.time_write += INSTR_TIME_GET_DOUBLE(bufusage->time_write);
 		e->counters.usage += usage;
 		SpinLockRelease(&e->mutex);
 	}
@@ -793,7 +801,7 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 	PG_RETURN_VOID();
 }
 
-#define PG_STAT_STATEMENTS_COLS		14
+#define PG_STAT_STATEMENTS_COLS		16
 
 /*
  * Retrieve statement statistics.
@@ -893,6 +901,8 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
+		values[i++] = Float8GetDatumFast(tmp.time_read);
+		values[i++] = Float8GetDatumFast(tmp.time_write);
 
 		Assert(i == PG_STAT_STATEMENTS_COLS);
 
diff --git a/contrib/pg_stat_statements/pg_stat_statements.control b/contrib/pg_stat_statements/pg_stat_statements.control
index 6f9a947..428fbb2 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.control
+++ b/contrib/pg_stat_statements/pg_stat_statements.control
@@ -1,5 +1,5 @@
 # pg_stat_statements extension
 comment = 'track execution statistics of all SQL statements executed'
-default_version = '1.0'
+default_version = '1.1'
 module_pathname = '$libdir/pg_stat_statements'
 relocatable = true
diff --git a/contrib/pg_test_timing/Makefile b/contrib/pg_test_timing/Makefile
new file mode 100644
index 0000000..b8b266a
--- /dev/null
+++ b/contrib/pg_test_timing/Makefile
@@ -0,0 +1,18 @@
+# contrib/pg_test_timing/Makefile
+
+PGFILEDESC = "pg_test_timing - test timing overhead"
+PGAPPICON = win32
+
+PROGRAM  = pg_test_timing
+OBJS = pg_test_timing.o
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_test_timing
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/pg_test_timing/pg_test_timing.c b/contrib/pg_test_timing/pg_test_timing.c
new file mode 100644
index 0000000..be511ce
--- /dev/null
+++ b/contrib/pg_test_timing/pg_test_timing.c
@@ -0,0 +1,149 @@
+/*
+ *	pg_test_timing.c
+ *		tests overhead and monotonicity of timing calls
+ */
+
+#include "postgres_fe.h"
+
+#include "getopt_long.h"
+#include "portability/instr_time.h"
+
+static const char *progname;
+
+static int32	test_duration = 3;
+
+static void handle_args(int argc, char *argv[]);
+static void test_timing(int32);
+
+int
+main(int argc, char *argv[])
+{
+	progname = get_progname(argv[0]);
+
+	handle_args(argc, argv);
+
+	test_timing(test_duration);
+
+	return 0;
+}
+
+static void
+handle_args(int argc, char *argv[])
+{
+	static struct option long_options[] = {
+		{"duration", required_argument, NULL, 'd'},
+		{NULL, 0, NULL, 0}
+	};
+	int			option;			/* Command line option */
+	int			optindex = 0;	/* used by getopt_long */
+
+	if (argc > 1)
+	{
+		if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0 ||
+			strcmp(argv[1], "-?") == 0)
+		{
+			printf("Usage: %s [-d DURATION]\n", progname);
+			exit(0);
+		}
+		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
+		{
+			puts("pg_test_timing (PostgreSQL) " PG_VERSION);
+			exit(0);
+		}
+	}
+
+	while ((option = getopt_long(argc, argv, "d:",
+								 long_options, &optindex)) != -1)
+	{
+		switch (option)
+		{
+			case 'd':
+				test_duration = atoi(optarg);
+				break;
+
+			default:
+				fprintf(stderr, "Try \"%s --help\" for more information.\n",
+						progname);
+				exit(1);
+				break;
+		}
+	}
+
+	if (argc > optind)
+	{
+		fprintf(stderr,
+				"%s: too many command-line arguments (first is \"%s\")\n",
+				progname, argv[optind]);
+		fprintf(stderr, "Try \"%s --help\" for more information.\n",
+				progname);
+		exit(1);
+	}
+
+	if (test_duration > 0) {
+		printf("Testing timing overhead for %d seconds.\n", test_duration);
+	} else {
+		printf("Testing timing monotonicity until interrupted.\n");
+	}
+}
+
+static void
+test_timing(int32 duration)
+{
+	uint64 total_time;
+	int64 time_elapsed = 0;
+	uint64 loop_count = 0;
+	uint64 prev, cur;
+	int32 diff, i, bits, found;
+
+	instr_time start_time, end_time, temp;
+
+	static int64 histogram[32];
+
+	total_time = duration > 0 ? duration * 1000000 : 0;
+
+	INSTR_TIME_SET_CURRENT(start_time);
+	cur = INSTR_TIME_GET_MICROSEC(start_time);
+
+	while (time_elapsed < total_time)
+	{
+		prev = cur;
+		INSTR_TIME_SET_CURRENT(temp);
+		cur = INSTR_TIME_GET_MICROSEC(temp);
+		diff = cur - prev;
+
+		if (diff < 0) {
+			printf("Detected clock going backwards in time.\n");
+			printf("Time warp: %d microseconds\n", diff);
+			exit(1);
+		}
+
+		bits = 0;
+		while (diff) {
+			diff >>= 1;
+			bits++;
+		}
+		histogram[bits]++;
+
+		loop_count++;
+		INSTR_TIME_SUBTRACT(temp, start_time);
+		time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
+	}
+
+	INSTR_TIME_SET_CURRENT(end_time);
+
+	INSTR_TIME_SUBTRACT(end_time, start_time);
+
+	printf("Per timing duration including loop overhead: %0.2f ns\n",
+			INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
+	printf("Histogram of timing durations:\n");
+	printf("%9s: %10s %9s\n", "< usec", "count", "percent");
+
+	found = 0;
+    for (i = 31; i >= 0; i--) {
+        if (found || histogram[i]) {
+            found = 1;
+            printf("%9ld: %10ld %8.5f%%\n", 1l<<i, histogram[i],
+                ((double)histogram[i])*100/loop_count);
+        }
+    }
+}
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0cc3296..b7084d5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4174,6 +4174,25 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-track-iotiming" xreflabel="track_iotiming">
+      <term><varname>track_iotiming</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>track_iotiming</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Enables timing of database I/O calls.
+        This parameter is off by default, because it may cause significant
+        overhead if the platform doesn't support fast timing information.
+        Only superusers can change this setting.
+       </para>
+       <para>
+        You can use the <xref linkend="pgtesttiming"> tool to find out the
+        overhead of timing on your system.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-track-functions" xreflabel="track_functions">
       <term><varname>track_functions</varname> (<type>enum</type>)</term>
       <indexterm>
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..b418688 100644
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@@ -121,6 +121,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
  &pgstatstatements;
  &pgstattuple;
  &pgtestfsync;
+ &pgtesttiming;
  &pgtrgm;
  &pgupgrade;
  &seg;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b96dd65..38c9334 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -129,6 +129,7 @@
 <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
 <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
 <!ENTITY pgtestfsync     SYSTEM "pgtestfsync.sgml">
+<!ENTITY pgtesttiming    SYSTEM "pgtesttiming.sgml">
 <!ENTITY pgtrgm          SYSTEM "pgtrgm.sgml">
 <!ENTITY pgupgrade       SYSTEM "pgupgrade.sgml">
 <!ENTITY seg             SYSTEM "seg.sgml">
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index a12a9a2..a3c6a80 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -116,7 +116,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    <productname>PostgreSQL</productname>'s <firstterm>statistics collector</>
    is a subsystem that supports collection and reporting of information about
    server activity.  Presently, the collector can count accesses to tables
-   and indexes in both disk-block and individual-row terms.  It also tracks
+   and indexes in both disk-block and individual-row terms and time disk-block
+   accesses.  It also tracks
    the total number of rows in each table, and information about vacuum and
    analyze actions for each table.  It can also count calls to user-defined
    functions and the total time spent in each one.
@@ -145,6 +146,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   </para>
 
   <para>
+   The parameter <xref linkend="guc-track-iotiming"> enables timing of I/O
+   requests.
+  </para>
+
+  <para>
    The parameter <xref linkend="guc-track-functions"> enables tracking of
    usage of user-defined functions.
   </para>
@@ -402,8 +408,9 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       blocks read from that table, number of buffer hits, numbers of
       disk blocks read and buffer hits in all indexes of that table,
       numbers of disk blocks read and buffer hits from that table's
-      auxiliary TOAST table (if any), and numbers of disk blocks read
-      and buffer hits for the TOAST table's index.
+      auxiliary TOAST table (if any), numbers of disk blocks read
+      and buffer hits for the TOAST table's index and microseconds
+      spent reading the blocks for each category.
       </entry>
      </row>
 
@@ -423,7 +430,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       <entry><structname>pg_statio_all_indexes</><indexterm><primary>pg_statio_all_indexes</primary></indexterm></entry>
       <entry>For each index in the current database,
       the table and index OID, schema, table and index name,
-      numbers of disk blocks read and buffer hits in that index.
+      numbers of disk blocks read, microseconds spent reading the blocks
+      and buffer hits in that index.
       </entry>
      </row>
 
@@ -522,7 +530,10 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    handles disk I/O, data that is not in the
    <productname>PostgreSQL</> buffer cache might still reside in the
    kernel's I/O cache, and might therefore still be fetched without
-   requiring a physical read. Users interested in obtaining more
+   requiring a physical read.
+   Timing info shows how much user queries were delayed by buffer reads
+   in aggregate.
+   Users interested in obtaining more
    detailed information on <productname>PostgreSQL</> I/O behavior are
    advised to use the <productname>PostgreSQL</> statistics collector
    in combination with operating system utilities that allow insight
@@ -598,6 +609,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_db_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block fetch
+       requests for database
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_db_tuples_returned</function>(<type>oid</type>)</literal></entry>
       <entry><type>bigint</type></entry>
       <entry>
@@ -783,6 +803,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block requests
+       for table or index
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_last_vacuum_time</function>(<type>oid</type>)</literal></entry>
       <entry><type>timestamptz</type></entry>
       <entry>
@@ -924,6 +953,14 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_xact_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent waiting for  disk block requests for table or index, in the current transaction
+      </entry>
+     </row>
+
+     <row>
        <!-- See also the entry for this in func.sgml -->
       <entry><literal><function>pg_backend_pid()</function></literal></entry>
       <entry><type>integer</type></entry>
diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml
index 5a0230c..2d60bdb 100644
--- a/doc/src/sgml/pgstatstatements.sgml
+++ b/doc/src/sgml/pgstatstatements.sgml
@@ -141,6 +141,20 @@
       <entry>Total number of temp blocks writes by the statement</entry>
      </row>
 
+     <row>
+      <entry><structfield>time_read</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for reading blocks, in seconds</entry>
+     </row>
+
+     <row>
+      <entry><structfield>time_write</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for writing out dirty blocks, in seconds</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/pgtesttiming.sgml b/doc/src/sgml/pgtesttiming.sgml
new file mode 100644
index 0000000..697e215
--- /dev/null
+++ b/doc/src/sgml/pgtesttiming.sgml
@@ -0,0 +1,54 @@
+<!-- doc/src/sgml/pgtesttiming.sgml -->
+
+<sect1 id="pgtesttiming" xreflabel="pg_test_timing">
+ <title>pg_test_timing</title>
+
+ <indexterm zone="pgtesttiming">
+  <primary>pg_test_timing</primary>
+ </indexterm>
+
+ <para>
+  <application>pg_test_timing</> is a tool to measure the timing overhead
+  on your system and check that the system time never moves backwards.
+ </para>
+
+ <sect2>
+  <title>Usage</title>
+
+<synopsis>
+pg_test_timing [options]
+</synopsis>
+
+   <para>
+    <application>pg_test_timing</application> accepts the following
+    command-line options:
+
+    <variablelist>
+
+     <varlistentry>
+      <term><option>-d</option></term>
+      <term><option>--duration</option></term>
+      <listitem>
+       <para>
+        Specifies the number of seconds to run the test. Longer durations
+        give slightly better accuracy and have a higher probablity to
+        discover potential problems with the system clock. The default
+        test duration is 3 seconds.
+       </para>
+      </listitem>
+     </varlistentry>
+
+    </variablelist>
+   </para>
+
+ </sect2>
+
+ <sect2>
+  <title>Author</title>
+
+  <para>
+   Ants Aasma <email>ants.aasma@eesti.ee</email>
+  </para>
+ </sect2>
+
+</sect1>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 50ba20c..5a7c91b 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -415,15 +415,19 @@ CREATE VIEW pg_statio_all_tables AS
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS heap_blks_read,
             pg_stat_get_blocks_hit(C.oid) AS heap_blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS heap_blks_time,
             sum(pg_stat_get_blocks_fetched(I.indexrelid) -
                     pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_read,
             sum(pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_hit,
+            sum(pg_stat_get_blocks_time(I.indexrelid))::bigint AS idx_blks_time,
             pg_stat_get_blocks_fetched(T.oid) -
                     pg_stat_get_blocks_hit(T.oid) AS toast_blks_read,
             pg_stat_get_blocks_hit(T.oid) AS toast_blks_hit,
+            pg_stat_get_blocks_time(T.oid) AS toast_blks_time,
             pg_stat_get_blocks_fetched(X.oid) -
                     pg_stat_get_blocks_hit(X.oid) AS tidx_blks_read,
-            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit
+            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit,
+            pg_stat_get_blocks_time(X.oid) AS tidx_blks_time
     FROM pg_class C LEFT JOIN
             pg_index I ON C.oid = I.indrelid LEFT JOIN
             pg_class T ON C.reltoastrelid = T.oid LEFT JOIN
@@ -477,7 +481,8 @@ CREATE VIEW pg_statio_all_indexes AS
             I.relname AS indexrelname,
             pg_stat_get_blocks_fetched(I.oid) -
                     pg_stat_get_blocks_hit(I.oid) AS idx_blks_read,
-            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit
+            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit,
+            pg_stat_get_blocks_time(I.oid) AS idx_blks_time
     FROM pg_class C JOIN
             pg_index X ON C.oid = X.indrelid JOIN
             pg_class I ON I.oid = X.indexrelid
@@ -501,7 +506,8 @@ CREATE VIEW pg_statio_all_sequences AS
             C.relname AS relname,
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS blks_read,
-            pg_stat_get_blocks_hit(C.oid) AS blks_hit
+            pg_stat_get_blocks_hit(C.oid) AS blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS blks_time
     FROM pg_class C
             LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
     WHERE C.relkind = 'S';
@@ -568,6 +574,7 @@ CREATE VIEW pg_stat_database AS
             pg_stat_get_db_blocks_fetched(D.oid) -
                     pg_stat_get_db_blocks_hit(D.oid) AS blks_read,
             pg_stat_get_db_blocks_hit(D.oid) AS blks_hit,
+            pg_stat_get_db_blocks_time(D.oid) AS blks_time,
             pg_stat_get_db_tuples_returned(D.oid) AS tup_returned,
             pg_stat_get_db_tuples_fetched(D.oid) AS tup_fetched,
             pg_stat_get_db_tuples_inserted(D.oid) AS tup_inserted,
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8b48105..6a98820 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -1150,9 +1150,12 @@ ExplainNode(PlanState *planstate, List *ancestors,
 									 usage->local_blks_written);
 			bool		has_temp = (usage->temp_blks_read > 0 ||
 									usage->temp_blks_written);
+			bool		has_timing = (!INSTR_TIME_IS_ZERO(usage->time_read) ||
+									  !INSTR_TIME_IS_ZERO(usage->time_write));
+
 
 			/* Show only positive counter values. */
-			if (has_shared || has_local || has_temp)
+			if (has_shared || has_local || has_temp || has_timing)
 			{
 				appendStringInfoSpaces(es->str, es->indent * 2);
 				appendStringInfoString(es->str, "Buffers:");
@@ -1197,6 +1200,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 						appendStringInfo(es->str, " written=%ld",
 										 usage->temp_blks_written);
 				}
+				if (has_timing)
+				{
+					appendStringInfoString(es->str, " timing");
+					if (!INSTR_TIME_IS_ZERO(usage->time_read)) {
+						appendStringInfo(es->str, " read=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_read));
+					}
+					if (!INSTR_TIME_IS_ZERO(usage->time_write)) {
+						appendStringInfo(es->str, " write=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_write));
+					}
+				}
 				appendStringInfoChar(es->str, '\n');
 			}
 		}
@@ -1210,6 +1225,8 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			ExplainPropertyLong("Local Written Blocks", usage->local_blks_written, es);
 			ExplainPropertyLong("Temp Read Blocks", usage->temp_blks_read, es);
 			ExplainPropertyLong("Temp Written Blocks", usage->temp_blks_written, es);
+			ExplainPropertyFloat("Read Waits", INSTR_TIME_GET_MILLISEC(usage->time_read), 3, es);
+			ExplainPropertyFloat("Write Waits", INSTR_TIME_GET_MILLISEC(usage->time_write), 3, es);
 		}
 	}
 
diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c
index dde73b7..28c4b4c 100644
--- a/src/backend/executor/instrument.c
+++ b/src/backend/executor/instrument.c
@@ -135,4 +135,6 @@ BufferUsageAccumDiff(BufferUsage *dst,
 	dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
 	dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
 	dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
+	INSTR_TIME_ACCUM_DIFF(dst->time_read, add->time_read, sub->time_read);
+	INSTR_TIME_ACCUM_DIFF(dst->time_write, add->time_write, sub->time_write);
 }
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 323d42b..1845cdc 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3255,6 +3255,7 @@ pgstat_get_db_entry(Oid databaseid, bool create)
 		result->n_xact_rollback = 0;
 		result->n_blocks_fetched = 0;
 		result->n_blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->n_tuples_returned = 0;
 		result->n_tuples_fetched = 0;
 		result->n_tuples_inserted = 0;
@@ -3326,6 +3327,7 @@ pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry, Oid tableoid, bool create)
 		result->changes_since_analyze = 0;
 		result->blocks_fetched = 0;
 		result->blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->vacuum_timestamp = 0;
 		result->vacuum_count = 0;
 		result->autovac_vacuum_timestamp = 0;
@@ -4014,6 +4016,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze = tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched = tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit = tabmsg->t_counts.t_blocks_hit;
+			tabentry->blocks_time = tabmsg->t_counts.t_blocks_time;
 
 			tabentry->vacuum_timestamp = 0;
 			tabentry->vacuum_count = 0;
@@ -4041,6 +4044,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze += tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit += tabmsg->t_counts.t_blocks_hit;
+			INSTR_TIME_ADD(tabentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 		}
 
 		/* Clamp n_live_tuples in case of negative delta_live_tuples */
@@ -4058,6 +4062,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 		dbentry->n_tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
 		dbentry->n_blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 		dbentry->n_blocks_hit += tabmsg->t_counts.t_blocks_hit;
+		INSTR_TIME_ADD(dbentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 	}
 }
 
@@ -4171,6 +4176,7 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 	dbentry->n_xact_rollback = 0;
 	dbentry->n_blocks_fetched = 0;
 	dbentry->n_blocks_hit = 0;
+	INSTR_TIME_SET_ZERO(dbentry->blocks_time);
 	dbentry->n_tuples_returned = 0;
 	dbentry->n_tuples_fetched = 0;
 	dbentry->n_tuples_inserted = 0;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 8f68bcc..de3a1f0 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -67,6 +67,7 @@
 bool		zero_damaged_pages = false;
 int			bgwriter_lru_maxpages = 100;
 double		bgwriter_lru_multiplier = 2.0;
+bool		track_iotiming = false;
 
 /*
  * How many buffers PrefetchBuffer callers should try to stay ahead of their
@@ -86,7 +87,7 @@ static volatile BufferDesc *PinCountWaitBuf = NULL;
 static Buffer ReadBuffer_common(SMgrRelation reln, char relpersistence,
 				  ForkNumber forkNum, BlockNumber blockNum,
 				  ReadBufferMode mode, BufferAccessStrategy strategy,
-				  bool *hit);
+				  bool *hit, instr_time *io_time);
 static bool PinBuffer(volatile BufferDesc *buf, BufferAccessStrategy strategy);
 static void PinBuffer_Locked(volatile BufferDesc *buf);
 static void UnpinBuffer(volatile BufferDesc *buf, bool fixOwner);
@@ -224,6 +225,7 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 				   ReadBufferMode mode, BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 	Buffer		buf;
 
 	/* Open it at the smgr level if not already done */
@@ -245,9 +247,11 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 	 */
 	pgstat_count_buffer_read(reln);
 	buf = ReadBuffer_common(reln->rd_smgr, reln->rd_rel->relpersistence,
-							forkNum, blockNum, mode, strategy, &hit);
+							forkNum, blockNum, mode, strategy, &hit, &io_time);
 	if (hit)
 		pgstat_count_buffer_hit(reln);
+	else
+		pgstat_count_buffer_time(reln, io_time);
 	return buf;
 }
 
@@ -267,11 +271,12 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
 						  BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 
 	SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
 
 	return ReadBuffer_common(smgr, RELPERSISTENCE_PERMANENT, forkNum, blockNum,
-							 mode, strategy, &hit);
+							 mode, strategy, &hit, &io_time);
 }
 
 
@@ -279,19 +284,22 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
  * ReadBuffer_common -- common logic for all ReadBuffer variants
  *
  * *hit is set to true if the request was satisfied from shared buffer cache.
+ * If track_iotiming is enabled, *io_time is set to the time the read took.
  */
 static Buffer
 ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 				  BlockNumber blockNum, ReadBufferMode mode,
-				  BufferAccessStrategy strategy, bool *hit)
+				  BufferAccessStrategy strategy, bool *hit, instr_time *io_time)
 {
 	volatile BufferDesc *bufHdr;
 	Block		bufBlock;
 	bool		found;
 	bool		isExtend;
 	bool		isLocalBuf = SmgrIsTemp(smgr);
+	instr_time io_start, io_end;
 
 	*hit = false;
+	INSTR_TIME_SET_ZERO(*io_time);
 
 	/* Make sure we will have room to remember the buffer pin */
 	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
@@ -437,8 +445,18 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 			MemSet((char *) bufBlock, 0, BLCKSZ);
 		else
 		{
+			if (track_iotiming)
+				INSTR_TIME_SET_CURRENT(io_start);
+
 			smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
 
+			if (track_iotiming)
+			{
+				INSTR_TIME_SET_CURRENT(io_end);
+				INSTR_TIME_ACCUM_DIFF(*io_time, io_end, io_start);
+				INSTR_TIME_ADD(pgBufferUsage.time_read, *io_time);
+			}
+
 			/* check for garbage data */
 			if (!PageHeaderIsValid((PageHeader) bufBlock))
 			{
@@ -1860,6 +1878,7 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 {
 	XLogRecPtr	recptr;
 	ErrorContextCallback errcontext;
+	instr_time io_start, io_end;
 
 	/*
 	 * Acquire the buffer's io_in_progress lock.  If StartBufferIO returns
@@ -1907,12 +1926,21 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 	buf->flags &= ~BM_JUST_DIRTIED;
 	UnlockBufHdr(buf);
 
+	if (track_iotiming)
+		INSTR_TIME_SET_CURRENT(io_start);
+
 	smgrwrite(reln,
 			  buf->tag.forkNum,
 			  buf->tag.blockNum,
 			  (char *) BufHdrGetBlock(buf),
 			  false);
 
+	if (track_iotiming)
+	{
+		INSTR_TIME_SET_CURRENT(io_end);
+		INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_write, io_end, io_start);
+	}
+
 	pgBufferUsage.shared_blks_written++;
 
 	/*
@@ -2648,6 +2676,7 @@ WaitIO(volatile BufferDesc *buf)
 static bool
 StartBufferIO(volatile BufferDesc *buf, bool forInput)
 {
+	instr_time wait_start, wait_end;
 	Assert(!InProgressBuf);
 
 	for (;;)
@@ -2656,7 +2685,28 @@ StartBufferIO(volatile BufferDesc *buf, bool forInput)
 		 * Grab the io_in_progress lock so that other processes can wait for
 		 * me to finish the I/O.
 		 */
-		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		if (forInput && track_iotiming) {
+			/*
+			 * We need to time the lock wait to account for I/O waits where
+			 * someone else is doing the work for us. Conditional acquire
+			 * avoids double timing overhead when we do the I/O ourselves.
+			 */
+			if (!LWLockConditionalAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE)) {
+				INSTR_TIME_SET_CURRENT(wait_start);
+
+				LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+
+				/*
+				 * Only do backend local accounting, stats collector will get the
+				 * wait from the backend doing the I/O.
+				 */
+				INSTR_TIME_SET_CURRENT(wait_end);
+				INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_read, wait_end, wait_start);
+			}
+		} else {
+			LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		}
+
 
 		LockBufHdr(buf);
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index b4986d8..b6e7339 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -22,6 +22,7 @@
 #include "utils/builtins.h"
 #include "utils/inet.h"
 #include "utils/timestamp.h"
+#include "portability/instr_time.h"
 
 /* bogus ... these externs should be in a header file */
 extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
@@ -35,6 +36,7 @@ extern Datum pg_stat_get_live_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_dead_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS);
@@ -67,6 +69,7 @@ extern Datum pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_inserted(PG_FUNCTION_ARGS);
@@ -99,6 +102,7 @@ extern Datum pg_stat_get_xact_tuples_deleted(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_tuples_hot_updated(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS);
 
 extern Datum pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_function_time(PG_FUNCTION_ARGS);
@@ -289,6 +293,22 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	double		result;
+	PgStat_StatTabEntry *tabentry;
+
+	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
+		result = 0;
+	else
+		/* Cast overflows in about 300'000 years of io time */
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 {
 	Oid			relid = PG_GETARG_OID(0);
@@ -1083,6 +1103,22 @@ pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 
 
 Datum
+pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_StatDBEntry *dbentry;
+
+	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(dbentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+
+Datum
 pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS)
 {
 	Oid			dbid = PG_GETARG_OID(0);
@@ -1482,6 +1518,21 @@ pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_TableStatus *tabentry;
+
+	if ((tabentry = find_tabstat_entry(relid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->t_counts.t_blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS)
 {
 	Oid			funcid = PG_GETARG_OID(0);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 5c910dd..9f7c6b7 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1017,6 +1017,15 @@ static struct config_bool ConfigureNamesBool[] =
 		true,
 		NULL, NULL, NULL
 	},
+	{
+		{"track_iotiming", PGC_SUSET, STATS_COLLECTOR,
+			gettext_noop("Collects timing information for database IO activity."),
+			NULL
+		},
+		&track_iotiming,
+		false,
+		NULL, NULL, NULL
+	},
 
 	{
 		{"update_process_title", PGC_SUSET, STATS_COLLECTOR,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 315db46..9877afc 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -420,6 +420,7 @@
 
 #track_activities = on
 #track_counts = on
+#track_iotiming = off
 #track_functions = none			# none, pl, all
 #track_activity_query_size = 1024 	# (change requires restart)
 #update_process_title = on
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 355c61a..19342dd 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2555,6 +2555,8 @@ DATA(insert OID = 1934 (  pg_stat_get_blocks_fetched	PGNSP PGUID 12 1 0 0 0 f f
 DESCR("statistics: number of blocks fetched");
 DATA(insert OID = 1935 (  pg_stat_get_blocks_hit		PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_hit _null_ _null_ _null_ ));
 DESCR("statistics: number of blocks found in cache");
+DATA(insert OID = 3947 (  pg_stat_get_blocks_time		PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads");
 DATA(insert OID = 2781 (  pg_stat_get_last_vacuum_time PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 1184 "26" _null_ _null_ _null_ _null_	pg_stat_get_last_vacuum_time _null_ _null_ _null_ ));
 DESCR("statistics: last manual vacuum time for a table");
 DATA(insert OID = 2782 (  pg_stat_get_last_autovacuum_time PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 1184 "26" _null_ _null_ _null_ _null_	pg_stat_get_last_autovacuum_time _null_ _null_ _null_ ));
@@ -2609,6 +2611,8 @@ DATA(insert OID = 1944 (  pg_stat_get_db_blocks_fetched PGNSP PGUID 12 1 0 0 0 f
 DESCR("statistics: blocks fetched for database");
 DATA(insert OID = 1945 (  pg_stat_get_db_blocks_hit		PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_blocks_hit _null_ _null_ _null_ ));
 DESCR("statistics: blocks found in cache for database");
+DATA(insert OID = 3948 (  pg_stat_get_db_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads for database");
 DATA(insert OID = 2758 (  pg_stat_get_db_tuples_returned PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_tuples_returned _null_ _null_ _null_ ));
 DESCR("statistics: tuples returned for database");
 DATA(insert OID = 2759 (  pg_stat_get_db_tuples_fetched PGNSP PGUID 12 1 0 0 0 f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_tuples_fetched _null_ _null_ _null_ ));
@@ -2677,6 +2681,8 @@ DATA(insert OID = 3044 (  pg_stat_get_xact_blocks_fetched		PGNSP PGUID 12 1 0 0
 DESCR("statistics: number of blocks fetched in current transaction");
 DATA(insert OID = 3045 (  pg_stat_get_xact_blocks_hit			PGNSP PGUID 12 1 0 0 0 f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_blocks_hit _null_ _null_ _null_ ));
 DESCR("statistics: number of blocks found in cache in current transaction");
+DATA(insert OID = 3949 (  pg_stat_get_xact_blocks_time			PGNSP PGUID 12 1 0 0 0 f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads in current transaction");
 DATA(insert OID = 3046 (  pg_stat_get_xact_function_calls		PGNSP PGUID 12 1 0 0 0 f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_function_calls _null_ _null_ _null_ ));
 DESCR("statistics: number of function calls in current transaction");
 DATA(insert OID = 3047 (  pg_stat_get_xact_function_time		PGNSP PGUID 12 1 0 0 0 f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_function_time _null_ _null_ _null_ ));
diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index 9ecb544..0c26bef 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -26,6 +26,8 @@ typedef struct BufferUsage
 	long		local_blks_written;		/* # of local disk blocks written */
 	long		temp_blks_read; /* # of temp blocks read */
 	long		temp_blks_written;		/* # of temp blocks written */
+	instr_time	time_read;	/* time spent reading */
+	instr_time	time_write;	/* time spent writing */
 } BufferUsage;
 
 /* Flag bits included in InstrAlloc's instrument_options bitmask */
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index b8c6d82..777be45 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -95,6 +95,7 @@ typedef struct PgStat_TableCounts
 
 	PgStat_Counter t_blocks_fetched;
 	PgStat_Counter t_blocks_hit;
+	instr_time     t_blocks_time;
 } PgStat_TableCounts;
 
 /* Possible targets for resetting cluster-wide shared values */
@@ -496,6 +497,7 @@ typedef struct PgStat_StatDBEntry
 	PgStat_Counter n_xact_rollback;
 	PgStat_Counter n_blocks_fetched;
 	PgStat_Counter n_blocks_hit;
+	instr_time	blocks_time;
 	PgStat_Counter n_tuples_returned;
 	PgStat_Counter n_tuples_fetched;
 	PgStat_Counter n_tuples_inserted;
@@ -543,6 +545,7 @@ typedef struct PgStat_StatTabEntry
 
 	PgStat_Counter blocks_fetched;
 	PgStat_Counter blocks_hit;
+	instr_time	blocks_time;
 
 	TimestampTz vacuum_timestamp;		/* user initiated vacuum */
 	PgStat_Counter vacuum_count;
@@ -765,6 +768,13 @@ extern void pgstat_initstats(Relation rel);
 		if ((rel)->pgstat_info != NULL)								\
 			(rel)->pgstat_info->t_counts.t_blocks_hit++;			\
 	} while (0)
+#define pgstat_count_buffer_time(rel, io)							\
+	do {															\
+		if ((rel)->pgstat_info != NULL)								\
+			INSTR_TIME_ADD(											\
+				(rel)->pgstat_info->t_counts.t_blocks_time,			\
+				(io));												\
+	} while (0)
 
 extern void pgstat_count_heap_insert(Relation rel, int n);
 extern void pgstat_count_heap_update(Relation rel, bool hot);
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index a03c068..3b0f1b0 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -48,6 +48,7 @@ extern PGDLLIMPORT int NBuffers;
 extern bool zero_damaged_pages;
 extern int	bgwriter_lru_maxpages;
 extern double bgwriter_lru_multiplier;
+extern bool track_iotiming;
 extern int	target_prefetch_pages;
 
 /* in buf_init.c */
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 454e1f9..983df54 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1296,7 +1296,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_all_indexes             | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, pg_stat_get_numscans(i.oid) AS idx_scan, pg_stat_get_tuples_returned(i.oid) AS idx_tup_read, pg_stat_get_tuples_fetched(i.oid) AS idx_tup_fetch FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
  pg_stat_all_tables              | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, pg_stat_get_numscans(c.oid) AS seq_scan, pg_stat_get_tuples_returned(c.oid) AS seq_tup_read, (sum(pg_stat_get_numscans(i.indexrelid)))::bigint AS idx_scan, ((sum(pg_stat_get_tuples_fetched(i.indexrelid)))::bigint + pg_stat_get_tuples_fetched(c.oid)) AS idx_tup_fetch, pg_stat_get_tuples_inserted(c.oid) AS n_tup_ins, pg_stat_get_tuples_updated(c.oid) AS n_tup_upd, pg_stat_get_tuples_deleted(c.oid) AS n_tup_del, pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd, pg_stat_get_live_tuples(c.oid) AS n_live_tup, pg_stat_get_dead_tuples(c.oid) AS n_dead_tup, pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum, pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum, pg_stat_get_last_analyze_time(c.oid) AS last_analyze, pg_stat_get_last_autoanalyze_time(c.oid) AS last_autoanalyze, pg_stat_get_vacuum_count(c.oid) AS vacuum_count, pg_stat_get_autovacuum_count(c.oid) AS autovacuum_count, pg_stat_get_analyze_count(c.oid) AS analyze_count, pg_stat_get_autoanalyze_count(c.oid) AS autoanalyze_count FROM ((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname;
  pg_stat_bgwriter                | SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed, pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req, pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint, pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean, pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, pg_stat_get_buf_written_backend() AS buffers_backend, pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync, pg_stat_get_buf_alloc() AS buffers_alloc, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
- pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
+ pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_blocks_time(d.oid) AS blks_time, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
  pg_stat_database_conflicts      | SELECT d.oid AS datid, d.datname, pg_stat_get_db_conflict_tablespace(d.oid) AS confl_tablespace, pg_stat_get_db_conflict_lock(d.oid) AS confl_lock, pg_stat_get_db_conflict_snapshot(d.oid) AS confl_snapshot, pg_stat_get_db_conflict_bufferpin(d.oid) AS confl_bufferpin, pg_stat_get_db_conflict_startup_deadlock(d.oid) AS confl_deadlock FROM pg_database d;
  pg_stat_replication             | SELECT s.procpid, s.usesysid, u.rolname AS usename, s.application_name, s.client_addr, s.client_hostname, s.client_port, s.backend_start, w.state, w.sent_location, w.write_location, w.flush_location, w.replay_location, w.sync_priority, w.sync_state FROM pg_stat_get_activity(NULL::integer) s(datid, procpid, usesysid, application_name, current_query, waiting, xact_start, query_start, backend_start, client_addr, client_hostname, client_port), pg_authid u, pg_stat_get_wal_senders() w(procpid, state, sent_location, write_location, flush_location, replay_location, sync_priority, sync_state) WHERE ((s.usesysid = u.oid) AND (s.procpid = w.procpid));
  pg_stat_sys_indexes             | SELECT pg_stat_all_indexes.relid, pg_stat_all_indexes.indexrelid, pg_stat_all_indexes.schemaname, pg_stat_all_indexes.relname, pg_stat_all_indexes.indexrelname, pg_stat_all_indexes.idx_scan, pg_stat_all_indexes.idx_tup_read, pg_stat_all_indexes.idx_tup_fetch FROM pg_stat_all_indexes WHERE ((pg_stat_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_all_indexes.schemaname ~ '^pg_toast'::text));
@@ -1308,15 +1308,15 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_xact_sys_tables         | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_xact_all_tables.schemaname ~ '^pg_toast'::text));
  pg_stat_xact_user_functions     | SELECT p.oid AS funcid, n.nspname AS schemaname, p.proname AS funcname, pg_stat_get_xact_function_calls(p.oid) AS calls, (pg_stat_get_xact_function_time(p.oid) / 1000) AS total_time, (pg_stat_get_xact_function_self_time(p.oid) / 1000) AS self_time FROM (pg_proc p LEFT JOIN pg_namespace n ON ((n.oid = p.pronamespace))) WHERE ((p.prolang <> (12)::oid) AND (pg_stat_get_xact_function_calls(p.oid) IS NOT NULL));
  pg_stat_xact_user_tables        | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_stat_xact_all_tables.schemaname !~ '^pg_toast'::text));
- pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
- pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
- pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
- pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
- pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
- pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
- pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
+ pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit, pg_stat_get_blocks_time(i.oid) AS idx_blks_time FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
+ pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit, pg_stat_get_blocks_time(c.oid) AS blks_time FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
+ pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, pg_stat_get_blocks_time(c.oid) AS heap_blks_time, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (sum(pg_stat_get_blocks_time(i.indexrelid)))::bigint AS idx_blks_time, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, pg_stat_get_blocks_time(t.oid) AS toast_blks_time, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit, pg_stat_get_blocks_time(x.oid) AS tidx_blks_time FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
+ pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
+ pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
  pg_stats                        | SELECT n.nspname AS schemaname, c.relname AS tablename, a.attname, s.stainherit AS inherited, s.stanullfrac AS null_frac, s.stawidth AS avg_width, s.stadistinct AS n_distinct, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stavalues1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stavalues2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stavalues3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stavalues4 ELSE NULL::anyarray END AS most_common_vals, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stanumbers1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stanumbers2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stanumbers3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stanumbers4 ELSE NULL::real[] END AS most_common_freqs, CASE WHEN (s.stakind1 = 2) THEN s.stavalues1 WHEN (s.stakind2 = 2) THEN s.stavalues2 WHEN (s.stakind3 = 2) THEN s.stavalues3 WHEN (s.stakind4 = 2) THEN s.stavalues4 ELSE NULL::anyarray END AS histogram_bounds, CASE WHEN (s.stakind1 = 3) THEN s.stanumbers1[1] WHEN (s.stakind2 = 3) THEN s.stanumbers2[1] WHEN (s.stakind3 = 3) THEN s.stanumbers3[1] WHEN (s.stakind4 = 3) THEN s.stanumbers4[1] ELSE NULL::real END AS correlation FROM (((pg_statistic s JOIN pg_class c ON ((c.oid = s.starelid))) JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum)))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE ((NOT a.attisdropped) AND has_column_privilege(c.oid, a.attnum, 'select'::text));
  pg_tables                       | SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.relhastriggers AS hastriggers FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = 'r'::"char");
  pg_timezone_abbrevs             | SELECT pg_timezone_abbrevs.abbrev, pg_timezone_abbrevs.utc_offset, pg_timezone_abbrevs.is_dst FROM pg_timezone_abbrevs() pg_timezone_abbrevs(abbrev, utc_offset, is_dst);

diff --git a/contrib/Makefile b/contrib/Makefile
index 0c238aa..45b601c 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -35,6 +35,7 @@ SUBDIRS = \
 		pg_standby	\
 		pg_stat_statements \
 		pg_test_fsync	\
+		pg_test_timing	\
 		pg_trgm		\
 		pg_upgrade	\
 		pg_upgrade_support \
diff --git a/contrib/pg_test_timing/Makefile b/contrib/pg_test_timing/Makefile
new file mode 100644
index 0000000..b8b266a
--- /dev/null
+++ b/contrib/pg_test_timing/Makefile
@@ -0,0 +1,18 @@
+# contrib/pg_test_timing/Makefile
+
+PGFILEDESC = "pg_test_timing - test timing overhead"
+PGAPPICON = win32
+
+PROGRAM  = pg_test_timing
+OBJS = pg_test_timing.o
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_test_timing
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/pg_test_timing/pg_test_timing.c b/contrib/pg_test_timing/pg_test_timing.c
new file mode 100644
index 0000000..bcf3c3a
--- /dev/null
+++ b/contrib/pg_test_timing/pg_test_timing.c
@@ -0,0 +1,157 @@
+/*
+ *	pg_test_timing.c
+ *		tests overhead of timing calls and their monoticity:  that
+ * 		they always move forward
+ */
+
+#include "postgres_fe.h"
+
+#include "getopt_long.h"
+#include "portability/instr_time.h"
+
+static const char *progname;
+
+static int32 test_duration = 3;
+
+static void handle_args(int argc, char *argv[]);
+static void test_timing(int32);
+
+int
+main(int argc, char *argv[])
+{
+	progname = get_progname(argv[0]);
+
+	handle_args(argc, argv);
+
+	test_timing(test_duration);
+
+	return 0;
+}
+
+static void
+handle_args(int argc, char *argv[])
+{
+	static struct option long_options[] = {
+		{"duration", required_argument, NULL, 'd'},
+		{NULL, 0, NULL, 0}
+	};
+	int option;			/* Command line option */
+	int	optindex = 0;	/* used by getopt_long */
+
+	if (argc > 1)
+	{
+		if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0 ||
+			strcmp(argv[1], "-?") == 0)
+		{
+			printf("Usage: %s [-d DURATION]\n", progname);
+			exit(0);
+		}
+		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
+		{
+			puts("pg_test_timing (PostgreSQL) " PG_VERSION);
+			exit(0);
+		}
+	}
+
+	while ((option = getopt_long(argc, argv, "d:",
+								 long_options, &optindex)) != -1)
+	{
+		switch (option)
+		{
+			case 'd':
+				test_duration = atoi(optarg);
+				break;
+
+			default:
+				fprintf(stderr, "Try \"%s --help\" for more information.\n",
+						progname);
+				exit(1);
+				break;
+		}
+	}
+
+	if (argc > optind)
+	{
+		fprintf(stderr,
+				"%s: too many command-line arguments (first is \"%s\")\n",
+				progname, argv[optind]);
+		fprintf(stderr, "Try \"%s --help\" for more information.\n",
+				progname);
+		exit(1);
+	}
+
+	if (test_duration > 0)
+	{
+		printf("Testing timing overhead for %d seconds.\n", test_duration);
+	}
+	else
+	{
+		printf("Testing timing was interrupted.\n");
+	}
+}
+
+static void
+test_timing(int32 duration)
+{
+	uint64 total_time;
+	int64 time_elapsed = 0;
+	uint64 loop_count = 0;
+	uint64 prev, cur;
+	int32 diff, i, bits, found;
+
+	instr_time start_time, end_time, temp;
+
+	static int64 histogram[32];
+
+	total_time = duration > 0 ? duration * 1000000 : 0;
+
+	INSTR_TIME_SET_CURRENT(start_time);
+	cur = INSTR_TIME_GET_MICROSEC(start_time);
+
+	while (time_elapsed < total_time)
+	{
+		prev = cur;
+		INSTR_TIME_SET_CURRENT(temp);
+		cur = INSTR_TIME_GET_MICROSEC(temp);
+		diff = cur - prev;
+
+		if (diff < 0)
+		{
+			printf("Detected clock going backwards in time.\n");
+			printf("Time warp: %d microseconds\n", diff);
+			exit(1);
+		}
+
+		bits = 0;
+		while (diff)
+		{
+			diff >>= 1;
+			bits++;
+		}
+		histogram[bits]++;
+
+		loop_count++;
+		INSTR_TIME_SUBTRACT(temp, start_time);
+		time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
+	}
+
+	INSTR_TIME_SET_CURRENT(end_time);
+
+	INSTR_TIME_SUBTRACT(end_time, start_time);
+
+	printf("Per timing duration including loop overhead: %0.2f ns\n",
+			INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
+	printf("Histogram of timing durations:\n");
+	printf("%9s: %10s %9s\n", "< usec", "count", "percent");
+
+	found = 0;
+    for (i = 31; i >= 0; i--)
+    {
+        if (found || histogram[i])
+        {
+            found = 1;
+            printf("%9ld: %10ld %8.5f%%\n", 1l << i, histogram[i],
+                (double) histogram[i] * 100 / loop_count);
+        }
+    }
+}
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index adf09ca..b418688 100644
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@@ -121,6 +121,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
  &pgstatstatements;
  &pgstattuple;
  &pgtestfsync;
+ &pgtesttiming;
  &pgtrgm;
  &pgupgrade;
  &seg;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index b96dd65..38c9334 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -129,6 +129,7 @@
 <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
 <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">
 <!ENTITY pgtestfsync     SYSTEM "pgtestfsync.sgml">
+<!ENTITY pgtesttiming    SYSTEM "pgtesttiming.sgml">
 <!ENTITY pgtrgm          SYSTEM "pgtrgm.sgml">
 <!ENTITY pgupgrade       SYSTEM "pgupgrade.sgml">
 <!ENTITY seg             SYSTEM "seg.sgml">
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 8e695fd..5a8c6fc 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -770,7 +770,9 @@ ROLLBACK;
     network transmission costs and I/O conversion costs are not included.
     Second, the measurement overhead added by <command>EXPLAIN
     ANALYZE</command> can be significant, especially on machines with slow
-    <function>gettimeofday()</> operating-system calls.
+    <function>gettimeofday()</> operating-system calls. You can use the
+    <xref linkend="pgtesttiming"> tool to measure the overhead of timing
+    on your system.
    </para>
 
    <para>
diff --git a/doc/src/sgml/pgtesttiming.sgml b/doc/src/sgml/pgtesttiming.sgml
new file mode 100644
index 0000000..f330265
--- /dev/null
+++ b/doc/src/sgml/pgtesttiming.sgml
@@ -0,0 +1,116 @@
+<!-- doc/src/sgml/pgtesttiming.sgml -->
+
+<sect1 id="pgtesttiming" xreflabel="pg_test_timing">
+ <title>pg_test_timing</title>
+
+ <indexterm zone="pgtesttiming">
+  <primary>pg_test_timing</primary>
+ </indexterm>
+
+ <para>
+  <application>pg_test_timing</> is a tool to measure the timing overhead
+  on your system and confirm that the system time never moves backwards.
+ </para>
+
+ <sect2>
+  <title>Usage</title>
+
+<synopsis>
+pg_test_timing [options]
+</synopsis>
+
+   <para>
+    <application>pg_test_timing</application> accepts the following
+    command-line options:
+
+    <variablelist>
+
+     <varlistentry>
+      <term><option>-d</option></term>
+      <term><option>--duration</option></term>
+      <listitem>
+       <para>
+        Specifies the number of seconds to run the test. Longer durations
+        give slightly better accuracy, and are more likely to discover
+        problems with the system clock moving backwards. The default
+        test duration is 3 seconds.
+       </para>
+      </listitem>
+     </varlistentry>
+
+    </variablelist>
+   </para>
+
+ </sect2>
+
+ <sect2>
+  <title>Interpreting results</title>
+  <para>
+        Collecting accurate timing information on 
+        Linux includes the options tsc, hpet, and acpi_pm 
+  </para>
+  <para>
+        Good results will show most individual timing calls take less
+        than one nanoseconds, such as this example from an Intel i7-860
+        system using the tsc clock source:
+
+<screen>
+Testing timing overhead for 3 seconds.
+Per timing duration including loop overhead: 35.96 ns
+Histogram of timing durations:
+   < usec:      count   percent
+       16:          2  0.00000%
+        8:         13  0.00002%
+        4:        126  0.00015%
+        2:    2999652  3.59518%
+        1:   80435604 96.40465%
+</screen>
+
+  </para>
+ </sect2>
+
+ <sect2>
+  <title>Changing time sources</title>
+  <para>
+        On Linux systems, it's possible to change the clock source
+        used to collect timing data at any time.  A second example
+        shows the slowdown possible from switching to the slower acpi_pm
+        time source, on the same system used for the fast results above:
+
+<screen>
+# cat /sys/devices/system/clocksource/clocksource0/available_clocksource 
+tsc hpet acpi_pm
+# echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
+# pg_test_timing
+Per timing duration including loop overhead: 722.92 ns
+Histogram of timing durations:
+   < usec:      count   percent
+       16:          3  0.00007%
+        8:        563  0.01357%
+        4:       3241  0.07810%
+        2:    2990371 72.05956%
+        1:    1155682 27.84870%
+</screen>
+
+  </para>
+
+  <para>
+        The tsc clock source is the most accurate one available on current
+        generation CPUs.  However, trying to use it on older CPUs sometimes
+        resulted in the reported time being inconsistent among multiple cores.
+        Newer versions of Linux will check for this and switch to a slower,
+        more stable clock sources instead.  Older ones would allow using tsc
+        in situations where it's now known to be inaccurate, which can
+        result in system instability.
+  </para>
+ </sect2>
+
+ <sect2>
+  <title>Author</title>
+
+  <para>
+   Ants Aasma <email>ants.aasma@eesti.ee</email>
+  </para>
+ </sect2>
+
+</sect1>

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0ea9aeb..ea09f3b 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4205,6 +4205,25 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-track-iotiming" xreflabel="track_iotiming">
+      <term><varname>track_iotiming</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>track_iotiming</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Enables timing of database I/O calls.
+        This parameter is off by default, because it may cause significant
+        overhead if the platform doesn't support fast timing information.
+        Only superusers can change this setting.
+       </para>
+       <para>
+        You can use the <xref linkend="pgtesttiming"> tool to find out the
+        overhead of timing on your system.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-track-functions" xreflabel="track_functions">
       <term><varname>track_functions</varname> (<type>enum</type>)</term>
       <indexterm>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index cb13c8e..3821d37 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -116,7 +116,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    <productname>PostgreSQL</productname>'s <firstterm>statistics collector</>
    is a subsystem that supports collection and reporting of information about
    server activity.  Presently, the collector can count accesses to tables
-   and indexes in both disk-block and individual-row terms.  It also tracks
+   and indexes in both disk-block and individual-row terms and time disk-block
+   accesses.  It also tracks
    the total number of rows in each table, and information about vacuum and
    analyze actions for each table.  It can also count calls to user-defined
    functions and the total time spent in each one.
@@ -145,6 +146,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   </para>
 
   <para>
+   The parameter <xref linkend="guc-track-iotiming"> enables timing of I/O
+   requests.
+  </para>
+
+  <para>
    The parameter <xref linkend="guc-track-functions"> enables tracking of
    usage of user-defined functions.
   </para>
@@ -403,8 +409,9 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       blocks read from that table, number of buffer hits, numbers of
       disk blocks read and buffer hits in all indexes of that table,
       numbers of disk blocks read and buffer hits from that table's
-      auxiliary TOAST table (if any), and numbers of disk blocks read
-      and buffer hits for the TOAST table's index.
+      auxiliary TOAST table (if any), numbers of disk blocks read
+      and buffer hits for the TOAST table's index and microseconds
+      spent reading the blocks for each category.
       </entry>
      </row>
 
@@ -424,7 +431,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       <entry><structname>pg_statio_all_indexes</><indexterm><primary>pg_statio_all_indexes</primary></indexterm></entry>
       <entry>For each index in the current database,
       the table and index OID, schema, table and index name,
-      numbers of disk blocks read and buffer hits in that index.
+      numbers of disk blocks read, microseconds spent reading the blocks
+      and buffer hits in that index.
       </entry>
      </row>
 
@@ -523,7 +531,10 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    handles disk I/O, data that is not in the
    <productname>PostgreSQL</> buffer cache might still reside in the
    kernel's I/O cache, and might therefore still be fetched without
-   requiring a physical read. Users interested in obtaining more
+   requiring a physical read.
+   Timing info shows how much user queries were delayed by buffer reads
+   in aggregate.
+   Users interested in obtaining more
    detailed information on <productname>PostgreSQL</> I/O behavior are
    advised to use the <productname>PostgreSQL</> statistics collector
    in combination with operating system utilities that allow insight
@@ -795,6 +806,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_db_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block fetch
+       requests for database
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_db_tuples_returned</function>(<type>oid</type>)</literal></entry>
       <entry><type>bigint</type></entry>
       <entry>
@@ -1010,6 +1030,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block fetch requests
+       for table or index
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_last_vacuum_time</function>(<type>oid</type>)</literal></entry>
       <entry><type>timestamptz</type></entry>
       <entry>
@@ -1151,6 +1180,14 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_xact_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent waiting for  disk block requests for table or index, in the current transaction
+      </entry>
+     </row>
+
+     <row>
        <!-- See also the entry for this in func.sgml -->
       <entry><literal><function>pg_backend_pid()</function></literal></entry>
       <entry><type>integer</type></entry>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 30b0bd0..e0999d5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -415,15 +415,19 @@ CREATE VIEW pg_statio_all_tables AS
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS heap_blks_read,
             pg_stat_get_blocks_hit(C.oid) AS heap_blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS heap_blks_time,
             sum(pg_stat_get_blocks_fetched(I.indexrelid) -
                     pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_read,
             sum(pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_hit,
+            sum(pg_stat_get_blocks_time(I.indexrelid))::bigint AS idx_blks_time,
             pg_stat_get_blocks_fetched(T.oid) -
                     pg_stat_get_blocks_hit(T.oid) AS toast_blks_read,
             pg_stat_get_blocks_hit(T.oid) AS toast_blks_hit,
+            pg_stat_get_blocks_time(T.oid) AS toast_blks_time,
             pg_stat_get_blocks_fetched(X.oid) -
                     pg_stat_get_blocks_hit(X.oid) AS tidx_blks_read,
-            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit
+            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit,
+            pg_stat_get_blocks_time(X.oid) AS tidx_blks_time
     FROM pg_class C LEFT JOIN
             pg_index I ON C.oid = I.indrelid LEFT JOIN
             pg_class T ON C.reltoastrelid = T.oid LEFT JOIN
@@ -477,7 +481,8 @@ CREATE VIEW pg_statio_all_indexes AS
             I.relname AS indexrelname,
             pg_stat_get_blocks_fetched(I.oid) -
                     pg_stat_get_blocks_hit(I.oid) AS idx_blks_read,
-            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit
+            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit,
+            pg_stat_get_blocks_time(I.oid) AS idx_blks_time
     FROM pg_class C JOIN
             pg_index X ON C.oid = X.indrelid JOIN
             pg_class I ON I.oid = X.indexrelid
@@ -501,7 +506,8 @@ CREATE VIEW pg_statio_all_sequences AS
             C.relname AS relname,
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS blks_read,
-            pg_stat_get_blocks_hit(C.oid) AS blks_hit
+            pg_stat_get_blocks_hit(C.oid) AS blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS blks_time
     FROM pg_class C
             LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
     WHERE C.relkind = 'S';
@@ -570,6 +576,7 @@ CREATE VIEW pg_stat_database AS
             pg_stat_get_db_blocks_fetched(D.oid) -
                     pg_stat_get_db_blocks_hit(D.oid) AS blks_read,
             pg_stat_get_db_blocks_hit(D.oid) AS blks_hit,
+            pg_stat_get_db_blocks_time(D.oid) AS blks_time,
             pg_stat_get_db_tuples_returned(D.oid) AS tup_returned,
             pg_stat_get_db_tuples_fetched(D.oid) AS tup_fetched,
             pg_stat_get_db_tuples_inserted(D.oid) AS tup_inserted,
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index a1692f8..d99a2cc 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -1189,9 +1189,12 @@ ExplainNode(PlanState *planstate, List *ancestors,
 									 usage->local_blks_written);
 			bool		has_temp = (usage->temp_blks_read > 0 ||
 									usage->temp_blks_written);
+			bool		has_timing = (!INSTR_TIME_IS_ZERO(usage->time_read) ||
+									  !INSTR_TIME_IS_ZERO(usage->time_write));
+
 
 			/* Show only positive counter values. */
-			if (has_shared || has_local || has_temp)
+			if (has_shared || has_local || has_temp || has_timing)
 			{
 				appendStringInfoSpaces(es->str, es->indent * 2);
 				appendStringInfoString(es->str, "Buffers:");
@@ -1236,6 +1239,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 						appendStringInfo(es->str, " written=%ld",
 										 usage->temp_blks_written);
 				}
+				if (has_timing)
+				{
+					appendStringInfoString(es->str, " timing");
+					if (!INSTR_TIME_IS_ZERO(usage->time_read)) {
+						appendStringInfo(es->str, " read=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_read));
+					}
+					if (!INSTR_TIME_IS_ZERO(usage->time_write)) {
+						appendStringInfo(es->str, " write=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_write));
+					}
+				}
 				appendStringInfoChar(es->str, '\n');
 			}
 		}
@@ -1249,6 +1264,8 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			ExplainPropertyLong("Local Written Blocks", usage->local_blks_written, es);
 			ExplainPropertyLong("Temp Read Blocks", usage->temp_blks_read, es);
 			ExplainPropertyLong("Temp Written Blocks", usage->temp_blks_written, es);
+			ExplainPropertyFloat("Read Waits", INSTR_TIME_GET_MILLISEC(usage->time_read), 3, es);
+			ExplainPropertyFloat("Write Waits", INSTR_TIME_GET_MILLISEC(usage->time_write), 3, es);
 		}
 	}
 
diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c
index 2c749b1..2ab76b3 100644
--- a/src/backend/executor/instrument.c
+++ b/src/backend/executor/instrument.c
@@ -143,4 +143,6 @@ BufferUsageAccumDiff(BufferUsage *dst,
 	dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
 	dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
 	dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
+	INSTR_TIME_ACCUM_DIFF(dst->time_read, add->time_read, sub->time_read);
+	INSTR_TIME_ACCUM_DIFF(dst->time_write, add->time_write, sub->time_write);
 }
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index a53fc52..e9f6a3b 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3338,6 +3338,7 @@ pgstat_get_db_entry(Oid databaseid, bool create)
 		result->n_xact_rollback = 0;
 		result->n_blocks_fetched = 0;
 		result->n_blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->n_tuples_returned = 0;
 		result->n_tuples_fetched = 0;
 		result->n_tuples_inserted = 0;
@@ -3412,6 +3413,7 @@ pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry, Oid tableoid, bool create)
 		result->changes_since_analyze = 0;
 		result->blocks_fetched = 0;
 		result->blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->vacuum_timestamp = 0;
 		result->vacuum_count = 0;
 		result->autovac_vacuum_timestamp = 0;
@@ -4100,6 +4102,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze = tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched = tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit = tabmsg->t_counts.t_blocks_hit;
+			tabentry->blocks_time = tabmsg->t_counts.t_blocks_time;
 
 			tabentry->vacuum_timestamp = 0;
 			tabentry->vacuum_count = 0;
@@ -4127,6 +4130,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze += tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit += tabmsg->t_counts.t_blocks_hit;
+			INSTR_TIME_ADD(tabentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 		}
 
 		/* Clamp n_live_tuples in case of negative delta_live_tuples */
@@ -4144,6 +4148,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 		dbentry->n_tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
 		dbentry->n_blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 		dbentry->n_blocks_hit += tabmsg->t_counts.t_blocks_hit;
+		INSTR_TIME_ADD(dbentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 	}
 }
 
@@ -4257,6 +4262,7 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 	dbentry->n_xact_rollback = 0;
 	dbentry->n_blocks_fetched = 0;
 	dbentry->n_blocks_hit = 0;
+	INSTR_TIME_SET_ZERO(dbentry->blocks_time);
 	dbentry->n_tuples_returned = 0;
 	dbentry->n_tuples_fetched = 0;
 	dbentry->n_tuples_inserted = 0;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 1adb6d3..22d4612 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -67,6 +67,7 @@
 bool		zero_damaged_pages = false;
 int			bgwriter_lru_maxpages = 100;
 double		bgwriter_lru_multiplier = 2.0;
+bool		track_iotiming = false;
 
 /*
  * How many buffers PrefetchBuffer callers should try to stay ahead of their
@@ -86,7 +87,7 @@ static volatile BufferDesc *PinCountWaitBuf = NULL;
 static Buffer ReadBuffer_common(SMgrRelation reln, char relpersistence,
 				  ForkNumber forkNum, BlockNumber blockNum,
 				  ReadBufferMode mode, BufferAccessStrategy strategy,
-				  bool *hit);
+				  bool *hit, instr_time *io_time);
 static bool PinBuffer(volatile BufferDesc *buf, BufferAccessStrategy strategy);
 static void PinBuffer_Locked(volatile BufferDesc *buf);
 static void UnpinBuffer(volatile BufferDesc *buf, bool fixOwner);
@@ -224,6 +225,7 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 				   ReadBufferMode mode, BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 	Buffer		buf;
 
 	/* Open it at the smgr level if not already done */
@@ -245,9 +247,11 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 	 */
 	pgstat_count_buffer_read(reln);
 	buf = ReadBuffer_common(reln->rd_smgr, reln->rd_rel->relpersistence,
-							forkNum, blockNum, mode, strategy, &hit);
+							forkNum, blockNum, mode, strategy, &hit, &io_time);
 	if (hit)
 		pgstat_count_buffer_hit(reln);
+	else
+		pgstat_count_buffer_time(reln, io_time);
 	return buf;
 }
 
@@ -267,11 +271,12 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
 						  BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 
 	SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
 
 	return ReadBuffer_common(smgr, RELPERSISTENCE_PERMANENT, forkNum, blockNum,
-							 mode, strategy, &hit);
+							 mode, strategy, &hit, &io_time);
 }
 
 
@@ -279,19 +284,22 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
  * ReadBuffer_common -- common logic for all ReadBuffer variants
  *
  * *hit is set to true if the request was satisfied from shared buffer cache.
+ * If track_iotiming is enabled, *io_time is set to the time the read took.
  */
 static Buffer
 ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 				  BlockNumber blockNum, ReadBufferMode mode,
-				  BufferAccessStrategy strategy, bool *hit)
+				  BufferAccessStrategy strategy, bool *hit, instr_time *io_time)
 {
 	volatile BufferDesc *bufHdr;
 	Block		bufBlock;
 	bool		found;
 	bool		isExtend;
 	bool		isLocalBuf = SmgrIsTemp(smgr);
+	instr_time io_start, io_end;
 
 	*hit = false;
+	INSTR_TIME_SET_ZERO(*io_time);
 
 	/* Make sure we will have room to remember the buffer pin */
 	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
@@ -437,8 +445,18 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 			MemSet((char *) bufBlock, 0, BLCKSZ);
 		else
 		{
+			if (track_iotiming)
+				INSTR_TIME_SET_CURRENT(io_start);
+
 			smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
 
+			if (track_iotiming)
+			{
+				INSTR_TIME_SET_CURRENT(io_end);
+				INSTR_TIME_ACCUM_DIFF(*io_time, io_end, io_start);
+				INSTR_TIME_ADD(pgBufferUsage.time_read, *io_time);
+			}
+
 			/* check for garbage data */
 			if (!PageHeaderIsValid((PageHeader) bufBlock))
 			{
@@ -1873,6 +1891,7 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 {
 	XLogRecPtr	recptr;
 	ErrorContextCallback errcontext;
+	instr_time io_start, io_end;
 
 	/*
 	 * Acquire the buffer's io_in_progress lock.  If StartBufferIO returns
@@ -1920,12 +1939,21 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 	buf->flags &= ~BM_JUST_DIRTIED;
 	UnlockBufHdr(buf);
 
+	if (track_iotiming)
+		INSTR_TIME_SET_CURRENT(io_start);
+
 	smgrwrite(reln,
 			  buf->tag.forkNum,
 			  buf->tag.blockNum,
 			  (char *) BufHdrGetBlock(buf),
 			  false);
 
+	if (track_iotiming)
+	{
+		INSTR_TIME_SET_CURRENT(io_end);
+		INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_write, io_end, io_start);
+	}
+
 	pgBufferUsage.shared_blks_written++;
 
 	/*
@@ -2669,6 +2697,7 @@ WaitIO(volatile BufferDesc *buf)
 static bool
 StartBufferIO(volatile BufferDesc *buf, bool forInput)
 {
+	instr_time wait_start, wait_end;
 	Assert(!InProgressBuf);
 
 	for (;;)
@@ -2677,7 +2706,28 @@ StartBufferIO(volatile BufferDesc *buf, bool forInput)
 		 * Grab the io_in_progress lock so that other processes can wait for
 		 * me to finish the I/O.
 		 */
-		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		if (forInput && track_iotiming) {
+			/*
+			 * We need to time the lock wait to account for I/O waits where
+			 * someone else is doing the work for us. Conditional acquire
+			 * avoids double timing overhead when we do the I/O ourselves.
+			 */
+			if (!LWLockConditionalAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE)) {
+				INSTR_TIME_SET_CURRENT(wait_start);
+
+				LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+
+				/*
+				 * Only do backend local accounting, stats collector will get the
+				 * wait from the backend doing the I/O.
+				 */
+				INSTR_TIME_SET_CURRENT(wait_end);
+				INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_read, wait_end, wait_start);
+			}
+		} else {
+			LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		}
+
 
 		LockBufHdr(buf);
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 68b2527..d0b6c57 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -22,6 +22,7 @@
 #include "utils/builtins.h"
 #include "utils/inet.h"
 #include "utils/timestamp.h"
+#include "portability/instr_time.h"
 
 /* bogus ... these externs should be in a header file */
 extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
@@ -35,6 +36,7 @@ extern Datum pg_stat_get_live_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_dead_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS);
@@ -67,6 +69,7 @@ extern Datum pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_inserted(PG_FUNCTION_ARGS);
@@ -102,6 +105,7 @@ extern Datum pg_stat_get_xact_tuples_deleted(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_tuples_hot_updated(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS);
 
 extern Datum pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_function_time(PG_FUNCTION_ARGS);
@@ -292,6 +296,22 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	double		result;
+	PgStat_StatTabEntry *tabentry;
+
+	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
+		result = 0;
+	else
+		/* Cast overflows in about 300'000 years of io time */
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 {
 	Oid			relid = PG_GETARG_OID(0);
@@ -1120,6 +1140,22 @@ pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 
 
 Datum
+pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_StatDBEntry *dbentry;
+
+	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(dbentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+
+Datum
 pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS)
 {
 	Oid			dbid = PG_GETARG_OID(0);
@@ -1565,6 +1601,21 @@ pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_TableStatus *tabentry;
+
+	if ((tabentry = find_tabstat_entry(relid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->t_counts.t_blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS)
 {
 	Oid			funcid = PG_GETARG_OID(0);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 7df5292..850f595 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1017,6 +1017,15 @@ static struct config_bool ConfigureNamesBool[] =
 		true,
 		NULL, NULL, NULL
 	},
+	{
+		{"track_iotiming", PGC_SUSET, STATS_COLLECTOR,
+			gettext_noop("Collects timing information for database IO activity."),
+			NULL
+		},
+		&track_iotiming,
+		false,
+		NULL, NULL, NULL
+	},
 
 	{
 		{"update_process_title", PGC_SUSET, STATS_COLLECTOR,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 400c52b..8cdc0ab 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -420,6 +420,7 @@
 
 #track_activities = on
 #track_counts = on
+#track_iotiming = off
 #track_functions = none			# none, pl, all
 #track_activity_query_size = 1024 	# (change requires restart)
 #update_process_title = on
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 8700d0d..4e58c8c 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2672,6 +2672,12 @@ DATA(insert OID = 3063 ( pg_stat_get_buf_fsync_backend PGNSP PGUID 12 1 0 0 0 f
 DESCR("statistics: number of backend buffer writes that did their own fsync");
 DATA(insert OID = 2859 ( pg_stat_get_buf_alloc			PGNSP PGUID 12 1 0 0 0 f f f f t f s 0 0 20 "" _null_ _null_ _null_ _null_ pg_stat_get_buf_alloc _null_ _null_ _null_ ));
 DESCR("statistics: number of buffer allocations");
+DATA(insert OID = 3947 (  pg_stat_get_blocks_time		PGNSP PGUID 12 1 0 0 0 f f f t f f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads");
+DATA(insert OID = 3948 (  pg_stat_get_db_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f t f f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads for database");
+DATA(insert OID = 3949 (  pg_stat_get_xact_blocks_time			PGNSP PGUID 12 1 0 0 0 f f f t f f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads in current transaction");
 
 DATA(insert OID = 2978 (  pg_stat_get_function_calls		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_function_calls _null_ _null_ _null_ ));
 DESCR("statistics: number of function calls");
diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index 084302e..fea87ff 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -26,6 +26,8 @@ typedef struct BufferUsage
 	long		local_blks_written;		/* # of local disk blocks written */
 	long		temp_blks_read; /* # of temp blocks read */
 	long		temp_blks_written;		/* # of temp blocks written */
+	instr_time	time_read;	/* time spent reading */
+	instr_time	time_write;	/* time spent writing */
 } BufferUsage;
 
 /* Flag bits included in InstrAlloc's instrument_options bitmask */
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 1281bd8..175b5df 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -97,6 +97,7 @@ typedef struct PgStat_TableCounts
 
 	PgStat_Counter t_blocks_fetched;
 	PgStat_Counter t_blocks_hit;
+	instr_time     t_blocks_time;
 } PgStat_TableCounts;
 
 /* Possible targets for resetting cluster-wide shared values */
@@ -522,6 +523,7 @@ typedef struct PgStat_StatDBEntry
 	PgStat_Counter n_xact_rollback;
 	PgStat_Counter n_blocks_fetched;
 	PgStat_Counter n_blocks_hit;
+	instr_time	blocks_time;
 	PgStat_Counter n_tuples_returned;
 	PgStat_Counter n_tuples_fetched;
 	PgStat_Counter n_tuples_inserted;
@@ -573,6 +575,7 @@ typedef struct PgStat_StatTabEntry
 
 	PgStat_Counter blocks_fetched;
 	PgStat_Counter blocks_hit;
+	instr_time	blocks_time;
 
 	TimestampTz vacuum_timestamp;		/* user initiated vacuum */
 	PgStat_Counter vacuum_count;
@@ -816,6 +819,13 @@ extern void pgstat_initstats(Relation rel);
 		if ((rel)->pgstat_info != NULL)								\
 			(rel)->pgstat_info->t_counts.t_blocks_hit++;			\
 	} while (0)
+#define pgstat_count_buffer_time(rel, io)							\
+	do {															\
+		if ((rel)->pgstat_info != NULL)								\
+			INSTR_TIME_ADD(											\
+				(rel)->pgstat_info->t_counts.t_blocks_time,			\
+				(io));												\
+	} while (0)
 
 extern void pgstat_count_heap_insert(Relation rel, int n);
 extern void pgstat_count_heap_update(Relation rel, bool hot);
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index de1bbd0..d72bad9 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -48,6 +48,7 @@ extern PGDLLIMPORT int NBuffers;
 extern bool zero_damaged_pages;
 extern int	bgwriter_lru_maxpages;
 extern double bgwriter_lru_multiplier;
+extern bool track_iotiming;
 extern int	target_prefetch_pages;
 
 /* in buf_init.c */
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 0275a0e..f0aa424 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1296,7 +1296,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_all_indexes             | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, pg_stat_get_numscans(i.oid) AS idx_scan, pg_stat_get_tuples_returned(i.oid) AS idx_tup_read, pg_stat_get_tuples_fetched(i.oid) AS idx_tup_fetch FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
  pg_stat_all_tables              | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, pg_stat_get_numscans(c.oid) AS seq_scan, pg_stat_get_tuples_returned(c.oid) AS seq_tup_read, (sum(pg_stat_get_numscans(i.indexrelid)))::bigint AS idx_scan, ((sum(pg_stat_get_tuples_fetched(i.indexrelid)))::bigint + pg_stat_get_tuples_fetched(c.oid)) AS idx_tup_fetch, pg_stat_get_tuples_inserted(c.oid) AS n_tup_ins, pg_stat_get_tuples_updated(c.oid) AS n_tup_upd, pg_stat_get_tuples_deleted(c.oid) AS n_tup_del, pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd, pg_stat_get_live_tuples(c.oid) AS n_live_tup, pg_stat_get_dead_tuples(c.oid) AS n_dead_tup, pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum, pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum, pg_stat_get_last_analyze_time(c.oid) AS last_analyze, pg_stat_get_last_autoanalyze_time(c.oid) AS last_autoanalyze, pg_stat_get_vacuum_count(c.oid) AS vacuum_count, pg_stat_get_autovacuum_count(c.oid) AS autovacuum_count, pg_stat_get_analyze_count(c.oid) AS analyze_count, pg_stat_get_autoanalyze_count(c.oid) AS autoanalyze_count FROM ((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname;
  pg_stat_bgwriter                | SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed, pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req, pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint, pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean, pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, pg_stat_get_buf_written_backend() AS buffers_backend, pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync, pg_stat_get_buf_alloc() AS buffers_alloc, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
- pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
+ pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_blocks_time(d.oid) AS blks_time, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
  pg_stat_database_conflicts      | SELECT d.oid AS datid, d.datname, pg_stat_get_db_conflict_tablespace(d.oid) AS confl_tablespace, pg_stat_get_db_conflict_lock(d.oid) AS confl_lock, pg_stat_get_db_conflict_snapshot(d.oid) AS confl_snapshot, pg_stat_get_db_conflict_bufferpin(d.oid) AS confl_bufferpin, pg_stat_get_db_conflict_startup_deadlock(d.oid) AS confl_deadlock FROM pg_database d;
  pg_stat_replication             | SELECT s.pid, s.usesysid, u.rolname AS usename, s.application_name, s.client_addr, s.client_hostname, s.client_port, s.backend_start, w.state, w.sent_location, w.write_location, w.flush_location, w.replay_location, w.sync_priority, w.sync_state FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, waiting, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port), pg_authid u, pg_stat_get_wal_senders() w(pid, state, sent_location, write_location, flush_location, replay_location, sync_priority, sync_state) WHERE ((s.usesysid = u.oid) AND (s.pid = w.pid));
  pg_stat_sys_indexes             | SELECT pg_stat_all_indexes.relid, pg_stat_all_indexes.indexrelid, pg_stat_all_indexes.schemaname, pg_stat_all_indexes.relname, pg_stat_all_indexes.indexrelname, pg_stat_all_indexes.idx_scan, pg_stat_all_indexes.idx_tup_read, pg_stat_all_indexes.idx_tup_fetch FROM pg_stat_all_indexes WHERE ((pg_stat_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_all_indexes.schemaname ~ '^pg_toast'::text));
@@ -1308,15 +1308,15 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_xact_sys_tables         | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_xact_all_tables.schemaname ~ '^pg_toast'::text));
  pg_stat_xact_user_functions     | SELECT p.oid AS funcid, n.nspname AS schemaname, p.proname AS funcname, pg_stat_get_xact_function_calls(p.oid) AS calls, (pg_stat_get_xact_function_time(p.oid) / 1000) AS total_time, (pg_stat_get_xact_function_self_time(p.oid) / 1000) AS self_time FROM (pg_proc p LEFT JOIN pg_namespace n ON ((n.oid = p.pronamespace))) WHERE ((p.prolang <> (12)::oid) AND (pg_stat_get_xact_function_calls(p.oid) IS NOT NULL));
  pg_stat_xact_user_tables        | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_stat_xact_all_tables.schemaname !~ '^pg_toast'::text));
- pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
- pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
- pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
- pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
- pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
- pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
- pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
+ pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit, pg_stat_get_blocks_time(i.oid) AS idx_blks_time FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
+ pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit, pg_stat_get_blocks_time(c.oid) AS blks_time FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
+ pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, pg_stat_get_blocks_time(c.oid) AS heap_blks_time, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (sum(pg_stat_get_blocks_time(i.indexrelid)))::bigint AS idx_blks_time, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, pg_stat_get_blocks_time(t.oid) AS toast_blks_time, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit, pg_stat_get_blocks_time(x.oid) AS tidx_blks_time FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
+ pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
+ pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
  pg_stats                        | SELECT n.nspname AS schemaname, c.relname AS tablename, a.attname, s.stainherit AS inherited, s.stanullfrac AS null_frac, s.stawidth AS avg_width, s.stadistinct AS n_distinct, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stavalues1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stavalues2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stavalues3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stavalues4 ELSE NULL::anyarray END AS most_common_vals, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stanumbers1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stanumbers2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stanumbers3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stanumbers4 ELSE NULL::real[] END AS most_common_freqs, CASE WHEN (s.stakind1 = 2) THEN s.stavalues1 WHEN (s.stakind2 = 2) THEN s.stavalues2 WHEN (s.stakind3 = 2) THEN s.stavalues3 WHEN (s.stakind4 = 2) THEN s.stavalues4 ELSE NULL::anyarray END AS histogram_bounds, CASE WHEN (s.stakind1 = 3) THEN s.stanumbers1[1] WHEN (s.stakind2 = 3) THEN s.stanumbers2[1] WHEN (s.stakind3 = 3) THEN s.stanumbers3[1] WHEN (s.stakind4 = 3) THEN s.stanumbers4[1] ELSE NULL::real END AS correlation FROM (((pg_statistic s JOIN pg_class c ON ((c.oid = s.starelid))) JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum)))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE ((NOT a.attisdropped) AND has_column_privilege(c.oid, a.attnum, 'select'::text));
  pg_tables                       | SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.relhastriggers AS hastriggers FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = 'r'::"char");
  pg_timezone_abbrevs             | SELECT pg_timezone_abbrevs.abbrev, pg_timezone_abbrevs.utc_offset, pg_timezone_abbrevs.is_dst FROM pg_timezone_abbrevs() pg_timezone_abbrevs(abbrev, utc_offset, is_dst);

diff --git a/contrib/pg_stat_statements/Makefile b/contrib/pg_stat_statements/Makefile
index e086fd8..971773e 100644
--- a/contrib/pg_stat_statements/Makefile
+++ b/contrib/pg_stat_statements/Makefile
@@ -4,7 +4,8 @@ MODULE_big = pg_stat_statements
 OBJS = pg_stat_statements.o
 
 EXTENSION = pg_stat_statements
-DATA = pg_stat_statements--1.0.sql pg_stat_statements--unpackaged--1.0.sql
+DATA = pg_stat_statements--1.1.sql pg_stat_statements--1.0--1.1.sql \
+       pg_stat_statements--unpackaged--1.0.sql
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
new file mode 100644
index 0000000..20bd5e3
--- /dev/null
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
@@ -0,0 +1,26 @@
+/* contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.1'" to load this file. \quit
+
+CREATE OR REPLACE FUNCTION pg_stat_statements(
+    OUT userid oid,
+    OUT dbid oid,
+    OUT query text,
+    OUT calls int8,
+    OUT total_time float8,
+    OUT rows int8,
+    OUT shared_blks_hit int8,
+    OUT shared_blks_read int8,
+    OUT shared_blks_written int8,
+    OUT local_blks_hit int8,
+    OUT local_blks_read int8,
+    OUT local_blks_written int8,
+    OUT temp_blks_read int8,
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
+)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0.sql
deleted file mode 100644
index 5294a01..0000000
--- a/contrib/pg_stat_statements/pg_stat_statements--1.0.sql
+++ /dev/null
@@ -1,39 +0,0 @@
-/* contrib/pg_stat_statements/pg_stat_statements--1.0.sql */
-
--- complain if script is sourced in psql, rather than via CREATE EXTENSION
-\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
-
--- Register functions.
-CREATE FUNCTION pg_stat_statements_reset()
-RETURNS void
-AS 'MODULE_PATHNAME'
-LANGUAGE C;
-
-CREATE FUNCTION pg_stat_statements(
-    OUT userid oid,
-    OUT dbid oid,
-    OUT query text,
-    OUT calls int8,
-    OUT total_time float8,
-    OUT rows int8,
-    OUT shared_blks_hit int8,
-    OUT shared_blks_read int8,
-    OUT shared_blks_written int8,
-    OUT local_blks_hit int8,
-    OUT local_blks_read int8,
-    OUT local_blks_written int8,
-    OUT temp_blks_read int8,
-    OUT temp_blks_written int8
-)
-RETURNS SETOF record
-AS 'MODULE_PATHNAME'
-LANGUAGE C;
-
--- Register a view on the function for ease of use.
-CREATE VIEW pg_stat_statements AS
-  SELECT * FROM pg_stat_statements();
-
-GRANT SELECT ON pg_stat_statements TO PUBLIC;
-
--- Don't want this to be available to non-superusers.
-REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
new file mode 100644
index 0000000..8bd2868
--- /dev/null
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
@@ -0,0 +1,41 @@
+/* contrib/pg_stat_statements/pg_stat_statements--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
+
+-- Register functions.
+CREATE FUNCTION pg_stat_statements_reset()
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+CREATE FUNCTION pg_stat_statements(
+    OUT userid oid,
+    OUT dbid oid,
+    OUT query text,
+    OUT calls int8,
+    OUT total_time float8,
+    OUT rows int8,
+    OUT shared_blks_hit int8,
+    OUT shared_blks_read int8,
+    OUT shared_blks_written int8,
+    OUT local_blks_hit int8,
+    OUT local_blks_read int8,
+    OUT local_blks_written int8,
+    OUT temp_blks_read int8,
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
+)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME'
+LANGUAGE C;
+
+-- Register a view on the function for ease of use.
+CREATE VIEW pg_stat_statements AS
+  SELECT * FROM pg_stat_statements();
+
+GRANT SELECT ON pg_stat_statements TO PUBLIC;
+
+-- Don't want this to be available to non-superusers.
+REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 434aa71..cdcf4e8 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -83,6 +83,8 @@ typedef struct Counters
 	int64		local_blks_written;		/* # of local disk blocks written */
 	int64		temp_blks_read; /* # of temp blocks read */
 	int64		temp_blks_written;		/* # of temp blocks written */
+	double		time_read;		/* time spent reading in seconds */
+	double		time_write;		/* time spent writing in seconds */
 	double		usage;			/* usage factor */
 } Counters;
 
@@ -616,9 +618,9 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 		instr_time	start;
 		instr_time	duration;
 		uint64		rows = 0;
-		BufferUsage bufusage;
+		BufferUsage bufusage_start, bufusage;
 
-		bufusage = pgBufferUsage;
+		bufusage_start = pgBufferUsage;
 		INSTR_TIME_SET_CURRENT(start);
 
 		nested_level++;
@@ -649,21 +651,25 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 
 		/* calc differences of buffer counters. */
 		bufusage.shared_blks_hit =
-			pgBufferUsage.shared_blks_hit - bufusage.shared_blks_hit;
+			pgBufferUsage.shared_blks_hit - bufusage_start.shared_blks_hit;
 		bufusage.shared_blks_read =
-			pgBufferUsage.shared_blks_read - bufusage.shared_blks_read;
+			pgBufferUsage.shared_blks_read - bufusage_start.shared_blks_read;
 		bufusage.shared_blks_written =
-			pgBufferUsage.shared_blks_written - bufusage.shared_blks_written;
+			pgBufferUsage.shared_blks_written - bufusage_start.shared_blks_written;
 		bufusage.local_blks_hit =
-			pgBufferUsage.local_blks_hit - bufusage.local_blks_hit;
+			pgBufferUsage.local_blks_hit - bufusage_start.local_blks_hit;
 		bufusage.local_blks_read =
-			pgBufferUsage.local_blks_read - bufusage.local_blks_read;
+			pgBufferUsage.local_blks_read - bufusage_start.local_blks_read;
 		bufusage.local_blks_written =
-			pgBufferUsage.local_blks_written - bufusage.local_blks_written;
+			pgBufferUsage.local_blks_written - bufusage_start.local_blks_written;
 		bufusage.temp_blks_read =
-			pgBufferUsage.temp_blks_read - bufusage.temp_blks_read;
+			pgBufferUsage.temp_blks_read - bufusage_start.temp_blks_read;
 		bufusage.temp_blks_written =
-			pgBufferUsage.temp_blks_written - bufusage.temp_blks_written;
+			pgBufferUsage.temp_blks_written - bufusage_start.temp_blks_written;
+		bufusage.time_read = pgBufferUsage.time_read;
+		INSTR_TIME_SUBTRACT(bufusage.time_read, bufusage_start.time_read);
+		bufusage.time_write = pgBufferUsage.time_write;
+		INSTR_TIME_SUBTRACT(bufusage.time_write, bufusage_start.time_write);
 
 		pgss_store(queryString, INSTR_TIME_GET_DOUBLE(duration), rows,
 				   &bufusage);
@@ -772,6 +778,8 @@ pgss_store(const char *query, double total_time, uint64 rows,
 		e->counters.local_blks_written += bufusage->local_blks_written;
 		e->counters.temp_blks_read += bufusage->temp_blks_read;
 		e->counters.temp_blks_written += bufusage->temp_blks_written;
+		e->counters.time_read +=  INSTR_TIME_GET_DOUBLE(bufusage->time_read);
+		e->counters.time_write += INSTR_TIME_GET_DOUBLE(bufusage->time_write);
 		e->counters.usage += usage;
 		SpinLockRelease(&e->mutex);
 	}
@@ -793,7 +801,7 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 	PG_RETURN_VOID();
 }
 
-#define PG_STAT_STATEMENTS_COLS		14
+#define PG_STAT_STATEMENTS_COLS		16
 
 /*
  * Retrieve statement statistics.
@@ -893,6 +901,8 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
+		values[i++] = Float8GetDatumFast(tmp.time_read);
+		values[i++] = Float8GetDatumFast(tmp.time_write);
 
 		Assert(i == PG_STAT_STATEMENTS_COLS);
 
diff --git a/contrib/pg_stat_statements/pg_stat_statements.control b/contrib/pg_stat_statements/pg_stat_statements.control
index 6f9a947..428fbb2 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.control
+++ b/contrib/pg_stat_statements/pg_stat_statements.control
@@ -1,5 +1,5 @@
 # pg_stat_statements extension
 comment = 'track execution statistics of all SQL statements executed'
-default_version = '1.0'
+default_version = '1.1'
 module_pathname = '$libdir/pg_stat_statements'
 relocatable = true
diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml
index 5a0230c..2d60bdb 100644
--- a/doc/src/sgml/pgstatstatements.sgml
+++ b/doc/src/sgml/pgstatstatements.sgml
@@ -141,6 +141,20 @@
       <entry>Total number of temp blocks writes by the statement</entry>
      </row>
 
+     <row>
+      <entry><structfield>time_read</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for reading blocks, in seconds</entry>
+     </row>
+
+     <row>
+      <entry><structfield>time_write</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for writing out dirty blocks, in seconds</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6e1378a..a275535 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4269,6 +4269,25 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-track-iotiming" xreflabel="track_iotiming">
+      <term><varname>track_iotiming</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>track_iotiming</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Enables timing of database I/O calls.
+        This parameter is off by default, because it may cause significant
+        overhead if the platform doesn't support fast timing information.
+        Only superusers can change this setting.
+       </para>
+       <para>
+        You can use the <xref linkend="pgtesttiming"> tool to find out the
+        overhead of timing on your system.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-track-functions" xreflabel="track_functions">
       <term><varname>track_functions</varname> (<type>enum</type>)</term>
       <indexterm>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index cb13c8e..3821d37 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -116,7 +116,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    <productname>PostgreSQL</productname>'s <firstterm>statistics collector</>
    is a subsystem that supports collection and reporting of information about
    server activity.  Presently, the collector can count accesses to tables
-   and indexes in both disk-block and individual-row terms.  It also tracks
+   and indexes in both disk-block and individual-row terms and time disk-block
+   accesses.  It also tracks
    the total number of rows in each table, and information about vacuum and
    analyze actions for each table.  It can also count calls to user-defined
    functions and the total time spent in each one.
@@ -145,6 +146,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   </para>
 
   <para>
+   The parameter <xref linkend="guc-track-iotiming"> enables timing of I/O
+   requests.
+  </para>
+
+  <para>
    The parameter <xref linkend="guc-track-functions"> enables tracking of
    usage of user-defined functions.
   </para>
@@ -403,8 +409,9 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       blocks read from that table, number of buffer hits, numbers of
       disk blocks read and buffer hits in all indexes of that table,
       numbers of disk blocks read and buffer hits from that table's
-      auxiliary TOAST table (if any), and numbers of disk blocks read
-      and buffer hits for the TOAST table's index.
+      auxiliary TOAST table (if any), numbers of disk blocks read
+      and buffer hits for the TOAST table's index and microseconds
+      spent reading the blocks for each category.
       </entry>
      </row>
 
@@ -424,7 +431,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
       <entry><structname>pg_statio_all_indexes</><indexterm><primary>pg_statio_all_indexes</primary></indexterm></entry>
       <entry>For each index in the current database,
       the table and index OID, schema, table and index name,
-      numbers of disk blocks read and buffer hits in that index.
+      numbers of disk blocks read, microseconds spent reading the blocks
+      and buffer hits in that index.
       </entry>
      </row>
 
@@ -523,7 +531,10 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    handles disk I/O, data that is not in the
    <productname>PostgreSQL</> buffer cache might still reside in the
    kernel's I/O cache, and might therefore still be fetched without
-   requiring a physical read. Users interested in obtaining more
+   requiring a physical read.
+   Timing info shows how much user queries were delayed by buffer reads
+   in aggregate.
+   Users interested in obtaining more
    detailed information on <productname>PostgreSQL</> I/O behavior are
    advised to use the <productname>PostgreSQL</> statistics collector
    in combination with operating system utilities that allow insight
@@ -795,6 +806,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_db_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block fetch
+       requests for database
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_db_tuples_returned</function>(<type>oid</type>)</literal></entry>
       <entry><type>bigint</type></entry>
       <entry>
@@ -1010,6 +1030,15 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent across all backends waiting for disk block fetch requests
+       for table or index
+      </entry>
+     </row>
+
+     <row>
       <entry><literal><function>pg_stat_get_last_vacuum_time</function>(<type>oid</type>)</literal></entry>
       <entry><type>timestamptz</type></entry>
       <entry>
@@ -1151,6 +1180,14 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
      </row>
 
      <row>
+      <entry><literal><function>pg_stat_get_xact_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Microseconds spent waiting for  disk block requests for table or index, in the current transaction
+      </entry>
+     </row>
+
+     <row>
        <!-- See also the entry for this in func.sgml -->
       <entry><literal><function>pg_backend_pid()</function></literal></entry>
       <entry><type>integer</type></entry>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 30b0bd0..e0999d5 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -415,15 +415,19 @@ CREATE VIEW pg_statio_all_tables AS
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS heap_blks_read,
             pg_stat_get_blocks_hit(C.oid) AS heap_blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS heap_blks_time,
             sum(pg_stat_get_blocks_fetched(I.indexrelid) -
                     pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_read,
             sum(pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_hit,
+            sum(pg_stat_get_blocks_time(I.indexrelid))::bigint AS idx_blks_time,
             pg_stat_get_blocks_fetched(T.oid) -
                     pg_stat_get_blocks_hit(T.oid) AS toast_blks_read,
             pg_stat_get_blocks_hit(T.oid) AS toast_blks_hit,
+            pg_stat_get_blocks_time(T.oid) AS toast_blks_time,
             pg_stat_get_blocks_fetched(X.oid) -
                     pg_stat_get_blocks_hit(X.oid) AS tidx_blks_read,
-            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit
+            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit,
+            pg_stat_get_blocks_time(X.oid) AS tidx_blks_time
     FROM pg_class C LEFT JOIN
             pg_index I ON C.oid = I.indrelid LEFT JOIN
             pg_class T ON C.reltoastrelid = T.oid LEFT JOIN
@@ -477,7 +481,8 @@ CREATE VIEW pg_statio_all_indexes AS
             I.relname AS indexrelname,
             pg_stat_get_blocks_fetched(I.oid) -
                     pg_stat_get_blocks_hit(I.oid) AS idx_blks_read,
-            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit
+            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit,
+            pg_stat_get_blocks_time(I.oid) AS idx_blks_time
     FROM pg_class C JOIN
             pg_index X ON C.oid = X.indrelid JOIN
             pg_class I ON I.oid = X.indexrelid
@@ -501,7 +506,8 @@ CREATE VIEW pg_statio_all_sequences AS
             C.relname AS relname,
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS blks_read,
-            pg_stat_get_blocks_hit(C.oid) AS blks_hit
+            pg_stat_get_blocks_hit(C.oid) AS blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS blks_time
     FROM pg_class C
             LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
     WHERE C.relkind = 'S';
@@ -570,6 +576,7 @@ CREATE VIEW pg_stat_database AS
             pg_stat_get_db_blocks_fetched(D.oid) -
                     pg_stat_get_db_blocks_hit(D.oid) AS blks_read,
             pg_stat_get_db_blocks_hit(D.oid) AS blks_hit,
+            pg_stat_get_db_blocks_time(D.oid) AS blks_time,
             pg_stat_get_db_tuples_returned(D.oid) AS tup_returned,
             pg_stat_get_db_tuples_fetched(D.oid) AS tup_fetched,
             pg_stat_get_db_tuples_inserted(D.oid) AS tup_inserted,
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 93b1f34..b848c30 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -1191,9 +1191,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 									 usage->local_blks_written > 0);
 			bool		has_temp = (usage->temp_blks_read > 0 ||
 									usage->temp_blks_written > 0);
+			bool		has_timing = (!INSTR_TIME_IS_ZERO(usage->time_read) ||
+									  !INSTR_TIME_IS_ZERO(usage->time_write));
 
 			/* Show only positive counter values. */
-			if (has_shared || has_local || has_temp)
+			if (has_shared || has_local || has_temp || has_timing)
 			{
 				appendStringInfoSpaces(es->str, es->indent * 2);
 				appendStringInfoString(es->str, "Buffers:");
@@ -1244,6 +1246,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 						appendStringInfo(es->str, " written=%ld",
 										 usage->temp_blks_written);
 				}
+				if (has_timing)
+				{
+					appendStringInfoString(es->str, " timing");
+					if (!INSTR_TIME_IS_ZERO(usage->time_read)) {
+						appendStringInfo(es->str, " read=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_read));
+					}
+					if (!INSTR_TIME_IS_ZERO(usage->time_write)) {
+						appendStringInfo(es->str, " write=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_write));
+					}
+				}
 				appendStringInfoChar(es->str, '\n');
 			}
 		}
@@ -1259,6 +1273,8 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			ExplainPropertyLong("Local Written Blocks", usage->local_blks_written, es);
 			ExplainPropertyLong("Temp Read Blocks", usage->temp_blks_read, es);
 			ExplainPropertyLong("Temp Written Blocks", usage->temp_blks_written, es);
+			ExplainPropertyFloat("Read Waits", INSTR_TIME_GET_MILLISEC(usage->time_read), 3, es);
+			ExplainPropertyFloat("Write Waits", INSTR_TIME_GET_MILLISEC(usage->time_write), 3, es);
 		}
 	}
 
diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c
index 6e9f450..92e56d1 100644
--- a/src/backend/executor/instrument.c
+++ b/src/backend/executor/instrument.c
@@ -145,4 +145,6 @@ BufferUsageAccumDiff(BufferUsage *dst,
 	dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
 	dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
 	dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
+	INSTR_TIME_ACCUM_DIFF(dst->time_read, add->time_read, sub->time_read);
+	INSTR_TIME_ACCUM_DIFF(dst->time_write, add->time_write, sub->time_write);
 }
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index a53fc52..e9f6a3b 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3338,6 +3338,7 @@ pgstat_get_db_entry(Oid databaseid, bool create)
 		result->n_xact_rollback = 0;
 		result->n_blocks_fetched = 0;
 		result->n_blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->n_tuples_returned = 0;
 		result->n_tuples_fetched = 0;
 		result->n_tuples_inserted = 0;
@@ -3412,6 +3413,7 @@ pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry, Oid tableoid, bool create)
 		result->changes_since_analyze = 0;
 		result->blocks_fetched = 0;
 		result->blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->vacuum_timestamp = 0;
 		result->vacuum_count = 0;
 		result->autovac_vacuum_timestamp = 0;
@@ -4100,6 +4102,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze = tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched = tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit = tabmsg->t_counts.t_blocks_hit;
+			tabentry->blocks_time = tabmsg->t_counts.t_blocks_time;
 
 			tabentry->vacuum_timestamp = 0;
 			tabentry->vacuum_count = 0;
@@ -4127,6 +4130,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze += tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit += tabmsg->t_counts.t_blocks_hit;
+			INSTR_TIME_ADD(tabentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 		}
 
 		/* Clamp n_live_tuples in case of negative delta_live_tuples */
@@ -4144,6 +4148,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 		dbentry->n_tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
 		dbentry->n_blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 		dbentry->n_blocks_hit += tabmsg->t_counts.t_blocks_hit;
+		INSTR_TIME_ADD(dbentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 	}
 }
 
@@ -4257,6 +4262,7 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 	dbentry->n_xact_rollback = 0;
 	dbentry->n_blocks_fetched = 0;
 	dbentry->n_blocks_hit = 0;
+	INSTR_TIME_SET_ZERO(dbentry->blocks_time);
 	dbentry->n_tuples_returned = 0;
 	dbentry->n_tuples_fetched = 0;
 	dbentry->n_tuples_inserted = 0;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 3924a51..a28d8e3 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -67,6 +67,7 @@
 bool		zero_damaged_pages = false;
 int			bgwriter_lru_maxpages = 100;
 double		bgwriter_lru_multiplier = 2.0;
+bool		track_iotiming = false;
 
 /*
  * How many buffers PrefetchBuffer callers should try to stay ahead of their
@@ -86,7 +87,7 @@ static volatile BufferDesc *PinCountWaitBuf = NULL;
 static Buffer ReadBuffer_common(SMgrRelation reln, char relpersistence,
 				  ForkNumber forkNum, BlockNumber blockNum,
 				  ReadBufferMode mode, BufferAccessStrategy strategy,
-				  bool *hit);
+				  bool *hit, instr_time *io_time);
 static bool PinBuffer(volatile BufferDesc *buf, BufferAccessStrategy strategy);
 static void PinBuffer_Locked(volatile BufferDesc *buf);
 static void UnpinBuffer(volatile BufferDesc *buf, bool fixOwner);
@@ -224,6 +225,7 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 				   ReadBufferMode mode, BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 	Buffer		buf;
 
 	/* Open it at the smgr level if not already done */
@@ -245,9 +247,11 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 	 */
 	pgstat_count_buffer_read(reln);
 	buf = ReadBuffer_common(reln->rd_smgr, reln->rd_rel->relpersistence,
-							forkNum, blockNum, mode, strategy, &hit);
+							forkNum, blockNum, mode, strategy, &hit, &io_time);
 	if (hit)
 		pgstat_count_buffer_hit(reln);
+	else
+		pgstat_count_buffer_time(reln, io_time);
 	return buf;
 }
 
@@ -267,11 +271,12 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
 						  BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 
 	SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
 
 	return ReadBuffer_common(smgr, RELPERSISTENCE_PERMANENT, forkNum, blockNum,
-							 mode, strategy, &hit);
+							 mode, strategy, &hit, &io_time);
 }
 
 
@@ -279,19 +284,22 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
  * ReadBuffer_common -- common logic for all ReadBuffer variants
  *
  * *hit is set to true if the request was satisfied from shared buffer cache.
+ * If track_iotiming is enabled, *io_time is set to the time the read took.
  */
 static Buffer
 ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 				  BlockNumber blockNum, ReadBufferMode mode,
-				  BufferAccessStrategy strategy, bool *hit)
+				  BufferAccessStrategy strategy, bool *hit, instr_time *io_time)
 {
 	volatile BufferDesc *bufHdr;
 	Block		bufBlock;
 	bool		found;
 	bool		isExtend;
 	bool		isLocalBuf = SmgrIsTemp(smgr);
+	instr_time io_start, io_end;
 
 	*hit = false;
+	INSTR_TIME_SET_ZERO(*io_time);
 
 	/* Make sure we will have room to remember the buffer pin */
 	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
@@ -437,8 +445,18 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 			MemSet((char *) bufBlock, 0, BLCKSZ);
 		else
 		{
+			if (track_iotiming)
+				INSTR_TIME_SET_CURRENT(io_start);
+
 			smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
 
+			if (track_iotiming)
+			{
+				INSTR_TIME_SET_CURRENT(io_end);
+				INSTR_TIME_ACCUM_DIFF(*io_time, io_end, io_start);
+				INSTR_TIME_ADD(pgBufferUsage.time_read, *io_time);
+			}
+
 			/* check for garbage data */
 			if (!PageHeaderIsValid((PageHeader) bufBlock))
 			{
@@ -1874,6 +1892,7 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 {
 	XLogRecPtr	recptr;
 	ErrorContextCallback errcontext;
+	instr_time io_start, io_end;
 
 	/*
 	 * Acquire the buffer's io_in_progress lock.  If StartBufferIO returns
@@ -1921,12 +1940,21 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 	buf->flags &= ~BM_JUST_DIRTIED;
 	UnlockBufHdr(buf);
 
+	if (track_iotiming)
+		INSTR_TIME_SET_CURRENT(io_start);
+
 	smgrwrite(reln,
 			  buf->tag.forkNum,
 			  buf->tag.blockNum,
 			  (char *) BufHdrGetBlock(buf),
 			  false);
 
+	if (track_iotiming)
+	{
+		INSTR_TIME_SET_CURRENT(io_end);
+		INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_write, io_end, io_start);
+	}
+
 	pgBufferUsage.shared_blks_written++;
 
 	/*
@@ -2670,6 +2698,7 @@ WaitIO(volatile BufferDesc *buf)
 static bool
 StartBufferIO(volatile BufferDesc *buf, bool forInput)
 {
+	instr_time wait_start, wait_end;
 	Assert(!InProgressBuf);
 
 	for (;;)
@@ -2678,7 +2707,28 @@ StartBufferIO(volatile BufferDesc *buf, bool forInput)
 		 * Grab the io_in_progress lock so that other processes can wait for
 		 * me to finish the I/O.
 		 */
-		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		if (forInput && track_iotiming) {
+			/*
+			 * We need to time the lock wait to account for I/O waits where
+			 * someone else is doing the work for us. Conditional acquire
+			 * avoids double timing overhead when we do the I/O ourselves.
+			 */
+			if (!LWLockConditionalAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE)) {
+				INSTR_TIME_SET_CURRENT(wait_start);
+
+				LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+
+				/*
+				 * Only do backend local accounting, stats collector will get the
+				 * wait from the backend doing the I/O.
+				 */
+				INSTR_TIME_SET_CURRENT(wait_end);
+				INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_read, wait_end, wait_start);
+			}
+		} else {
+			LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		}
+
 
 		LockBufHdr(buf);
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 68b2527..d0b6c57 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -22,6 +22,7 @@
 #include "utils/builtins.h"
 #include "utils/inet.h"
 #include "utils/timestamp.h"
+#include "portability/instr_time.h"
 
 /* bogus ... these externs should be in a header file */
 extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
@@ -35,6 +36,7 @@ extern Datum pg_stat_get_live_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_dead_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS);
@@ -67,6 +69,7 @@ extern Datum pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_inserted(PG_FUNCTION_ARGS);
@@ -102,6 +105,7 @@ extern Datum pg_stat_get_xact_tuples_deleted(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_tuples_hot_updated(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS);
 
 extern Datum pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_function_time(PG_FUNCTION_ARGS);
@@ -292,6 +296,22 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	double		result;
+	PgStat_StatTabEntry *tabentry;
+
+	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
+		result = 0;
+	else
+		/* Cast overflows in about 300'000 years of io time */
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 {
 	Oid			relid = PG_GETARG_OID(0);
@@ -1120,6 +1140,22 @@ pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 
 
 Datum
+pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_StatDBEntry *dbentry;
+
+	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(dbentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+
+Datum
 pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS)
 {
 	Oid			dbid = PG_GETARG_OID(0);
@@ -1565,6 +1601,21 @@ pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_TableStatus *tabentry;
+
+	if ((tabentry = find_tabstat_entry(relid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->t_counts.t_blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS)
 {
 	Oid			funcid = PG_GETARG_OID(0);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index a5becbe..5e32278 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1018,6 +1018,15 @@ static struct config_bool ConfigureNamesBool[] =
 		true,
 		NULL, NULL, NULL
 	},
+	{
+		{"track_iotiming", PGC_SUSET, STATS_COLLECTOR,
+			gettext_noop("Collects timing information for database IO activity."),
+			NULL
+		},
+		&track_iotiming,
+		false,
+		NULL, NULL, NULL
+	},
 
 	{
 		{"update_process_title", PGC_SUSET, STATS_COLLECTOR,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 96da086..cbae3bf 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -424,6 +424,7 @@
 
 #track_activities = on
 #track_counts = on
+#track_iotiming = off
 #track_functions = none			# none, pl, all
 #track_activity_query_size = 1024 	# (change requires restart)
 #update_process_title = on
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 8700d0d..47cad5a 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2672,6 +2672,12 @@ DATA(insert OID = 3063 ( pg_stat_get_buf_fsync_backend PGNSP PGUID 12 1 0 0 0 f
 DESCR("statistics: number of backend buffer writes that did their own fsync");
 DATA(insert OID = 2859 ( pg_stat_get_buf_alloc			PGNSP PGUID 12 1 0 0 0 f f f f t f s 0 0 20 "" _null_ _null_ _null_ _null_ pg_stat_get_buf_alloc _null_ _null_ _null_ ));
 DESCR("statistics: number of buffer allocations");
+DATA(insert OID = 3160 (  pg_stat_get_blocks_time		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads");
+DATA(insert OID = 3161 (  pg_stat_get_db_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads for database");
+DATA(insert OID = 3162 (  pg_stat_get_xact_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads in current transaction");
 
 DATA(insert OID = 2978 (  pg_stat_get_function_calls		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_function_calls _null_ _null_ _null_ ));
 DESCR("statistics: number of function calls");
diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index 066f684..ad13914 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -28,6 +28,8 @@ typedef struct BufferUsage
 	long		local_blks_written;		/* # of local disk blocks written */
 	long		temp_blks_read; /* # of temp blocks read */
 	long		temp_blks_written;		/* # of temp blocks written */
+	instr_time	time_read;	/* time spent reading */
+	instr_time	time_write;	/* time spent writing */
 } BufferUsage;
 
 /* Flag bits included in InstrAlloc's instrument_options bitmask */
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 1281bd8..175b5df 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -97,6 +97,7 @@ typedef struct PgStat_TableCounts
 
 	PgStat_Counter t_blocks_fetched;
 	PgStat_Counter t_blocks_hit;
+	instr_time     t_blocks_time;
 } PgStat_TableCounts;
 
 /* Possible targets for resetting cluster-wide shared values */
@@ -522,6 +523,7 @@ typedef struct PgStat_StatDBEntry
 	PgStat_Counter n_xact_rollback;
 	PgStat_Counter n_blocks_fetched;
 	PgStat_Counter n_blocks_hit;
+	instr_time	blocks_time;
 	PgStat_Counter n_tuples_returned;
 	PgStat_Counter n_tuples_fetched;
 	PgStat_Counter n_tuples_inserted;
@@ -573,6 +575,7 @@ typedef struct PgStat_StatTabEntry
 
 	PgStat_Counter blocks_fetched;
 	PgStat_Counter blocks_hit;
+	instr_time	blocks_time;
 
 	TimestampTz vacuum_timestamp;		/* user initiated vacuum */
 	PgStat_Counter vacuum_count;
@@ -816,6 +819,13 @@ extern void pgstat_initstats(Relation rel);
 		if ((rel)->pgstat_info != NULL)								\
 			(rel)->pgstat_info->t_counts.t_blocks_hit++;			\
 	} while (0)
+#define pgstat_count_buffer_time(rel, io)							\
+	do {															\
+		if ((rel)->pgstat_info != NULL)								\
+			INSTR_TIME_ADD(											\
+				(rel)->pgstat_info->t_counts.t_blocks_time,			\
+				(io));												\
+	} while (0)
 
 extern void pgstat_count_heap_insert(Relation rel, int n);
 extern void pgstat_count_heap_update(Relation rel, bool hot);
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index de1bbd0..d72bad9 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -48,6 +48,7 @@ extern PGDLLIMPORT int NBuffers;
 extern bool zero_damaged_pages;
 extern int	bgwriter_lru_maxpages;
 extern double bgwriter_lru_multiplier;
+extern bool track_iotiming;
 extern int	target_prefetch_pages;
 
 /* in buf_init.c */
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 0275a0e..f0aa424 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1296,7 +1296,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_all_indexes             | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, pg_stat_get_numscans(i.oid) AS idx_scan, pg_stat_get_tuples_returned(i.oid) AS idx_tup_read, pg_stat_get_tuples_fetched(i.oid) AS idx_tup_fetch FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
  pg_stat_all_tables              | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, pg_stat_get_numscans(c.oid) AS seq_scan, pg_stat_get_tuples_returned(c.oid) AS seq_tup_read, (sum(pg_stat_get_numscans(i.indexrelid)))::bigint AS idx_scan, ((sum(pg_stat_get_tuples_fetched(i.indexrelid)))::bigint + pg_stat_get_tuples_fetched(c.oid)) AS idx_tup_fetch, pg_stat_get_tuples_inserted(c.oid) AS n_tup_ins, pg_stat_get_tuples_updated(c.oid) AS n_tup_upd, pg_stat_get_tuples_deleted(c.oid) AS n_tup_del, pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd, pg_stat_get_live_tuples(c.oid) AS n_live_tup, pg_stat_get_dead_tuples(c.oid) AS n_dead_tup, pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum, pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum, pg_stat_get_last_analyze_time(c.oid) AS last_analyze, pg_stat_get_last_autoanalyze_time(c.oid) AS last_autoanalyze, pg_stat_get_vacuum_count(c.oid) AS vacuum_count, pg_stat_get_autovacuum_count(c.oid) AS autovacuum_count, pg_stat_get_analyze_count(c.oid) AS analyze_count, pg_stat_get_autoanalyze_count(c.oid) AS autoanalyze_count FROM ((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname;
  pg_stat_bgwriter                | SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed, pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req, pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint, pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean, pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, pg_stat_get_buf_written_backend() AS buffers_backend, pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync, pg_stat_get_buf_alloc() AS buffers_alloc, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
- pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
+ pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_blocks_time(d.oid) AS blks_time, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
  pg_stat_database_conflicts      | SELECT d.oid AS datid, d.datname, pg_stat_get_db_conflict_tablespace(d.oid) AS confl_tablespace, pg_stat_get_db_conflict_lock(d.oid) AS confl_lock, pg_stat_get_db_conflict_snapshot(d.oid) AS confl_snapshot, pg_stat_get_db_conflict_bufferpin(d.oid) AS confl_bufferpin, pg_stat_get_db_conflict_startup_deadlock(d.oid) AS confl_deadlock FROM pg_database d;
  pg_stat_replication             | SELECT s.pid, s.usesysid, u.rolname AS usename, s.application_name, s.client_addr, s.client_hostname, s.client_port, s.backend_start, w.state, w.sent_location, w.write_location, w.flush_location, w.replay_location, w.sync_priority, w.sync_state FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, waiting, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port), pg_authid u, pg_stat_get_wal_senders() w(pid, state, sent_location, write_location, flush_location, replay_location, sync_priority, sync_state) WHERE ((s.usesysid = u.oid) AND (s.pid = w.pid));
  pg_stat_sys_indexes             | SELECT pg_stat_all_indexes.relid, pg_stat_all_indexes.indexrelid, pg_stat_all_indexes.schemaname, pg_stat_all_indexes.relname, pg_stat_all_indexes.indexrelname, pg_stat_all_indexes.idx_scan, pg_stat_all_indexes.idx_tup_read, pg_stat_all_indexes.idx_tup_fetch FROM pg_stat_all_indexes WHERE ((pg_stat_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_all_indexes.schemaname ~ '^pg_toast'::text));
@@ -1308,15 +1308,15 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_xact_sys_tables         | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_xact_all_tables.schemaname ~ '^pg_toast'::text));
  pg_stat_xact_user_functions     | SELECT p.oid AS funcid, n.nspname AS schemaname, p.proname AS funcname, pg_stat_get_xact_function_calls(p.oid) AS calls, (pg_stat_get_xact_function_time(p.oid) / 1000) AS total_time, (pg_stat_get_xact_function_self_time(p.oid) / 1000) AS self_time FROM (pg_proc p LEFT JOIN pg_namespace n ON ((n.oid = p.pronamespace))) WHERE ((p.prolang <> (12)::oid) AND (pg_stat_get_xact_function_calls(p.oid) IS NOT NULL));
  pg_stat_xact_user_tables        | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_stat_xact_all_tables.schemaname !~ '^pg_toast'::text));
- pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
- pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
- pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
- pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
- pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
- pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
- pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
+ pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit, pg_stat_get_blocks_time(i.oid) AS idx_blks_time FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
+ pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit, pg_stat_get_blocks_time(c.oid) AS blks_time FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
+ pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, pg_stat_get_blocks_time(c.oid) AS heap_blks_time, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (sum(pg_stat_get_blocks_time(i.indexrelid)))::bigint AS idx_blks_time, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, pg_stat_get_blocks_time(t.oid) AS toast_blks_time, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit, pg_stat_get_blocks_time(x.oid) AS tidx_blks_time FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
+ pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
+ pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
  pg_stats                        | SELECT n.nspname AS schemaname, c.relname AS tablename, a.attname, s.stainherit AS inherited, s.stanullfrac AS null_frac, s.stawidth AS avg_width, s.stadistinct AS n_distinct, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stavalues1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stavalues2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stavalues3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stavalues4 ELSE NULL::anyarray END AS most_common_vals, CASE WHEN (s.stakind1 = ANY (ARRAY[1, 4])) THEN s.stanumbers1 WHEN (s.stakind2 = ANY (ARRAY[1, 4])) THEN s.stanumbers2 WHEN (s.stakind3 = ANY (ARRAY[1, 4])) THEN s.stanumbers3 WHEN (s.stakind4 = ANY (ARRAY[1, 4])) THEN s.stanumbers4 ELSE NULL::real[] END AS most_common_freqs, CASE WHEN (s.stakind1 = 2) THEN s.stavalues1 WHEN (s.stakind2 = 2) THEN s.stavalues2 WHEN (s.stakind3 = 2) THEN s.stavalues3 WHEN (s.stakind4 = 2) THEN s.stavalues4 ELSE NULL::anyarray END AS histogram_bounds, CASE WHEN (s.stakind1 = 3) THEN s.stanumbers1[1] WHEN (s.stakind2 = 3) THEN s.stanumbers2[1] WHEN (s.stakind3 = 3) THEN s.stanumbers3[1] WHEN (s.stakind4 = 3) THEN s.stanumbers4[1] ELSE NULL::real END AS correlation FROM (((pg_statistic s JOIN pg_class c ON ((c.oid = s.starelid))) JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum)))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE ((NOT a.attisdropped) AND has_column_privilege(c.oid, a.attnum, 'select'::text));
  pg_tables                       | SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.relhastriggers AS hastriggers FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = 'r'::"char");
  pg_timezone_abbrevs             | SELECT pg_timezone_abbrevs.abbrev, pg_timezone_abbrevs.utc_offset, pg_timezone_abbrevs.is_dst FROM pg_timezone_abbrevs() pg_timezone_abbrevs(abbrev, utc_offset, is_dst);

diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
index 223271d..f976419 100644
--- a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
@@ -28,7 +28,9 @@ CREATE FUNCTION pg_stat_statements(
     OUT local_blks_dirtied int8,
     OUT local_blks_written int8,
     OUT temp_blks_read int8,
-    OUT temp_blks_written int8
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
 )
 RETURNS SETOF record
 AS 'MODULE_PATHNAME'
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
index 1233736..f4bdf12 100644
--- a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
@@ -25,7 +25,9 @@ CREATE FUNCTION pg_stat_statements(
     OUT local_blks_dirtied int8,
     OUT local_blks_written int8,
     OUT temp_blks_read int8,
-    OUT temp_blks_written int8
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
 )
 RETURNS SETOF record
 AS 'MODULE_PATHNAME'
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 914fbf2..8e34740 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -85,6 +85,8 @@ typedef struct Counters
 	int64		local_blks_written;		/* # of local disk blocks written */
 	int64		temp_blks_read; /* # of temp blocks read */
 	int64		temp_blks_written;		/* # of temp blocks written */
+	double		time_read;		/* time spent reading in seconds */
+	double		time_write;		/* time spent writing in seconds */
 	double		usage;			/* usage factor */
 } Counters;
 
@@ -618,9 +620,9 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 		instr_time	start;
 		instr_time	duration;
 		uint64		rows = 0;
-		BufferUsage bufusage;
+		BufferUsage bufusage_start, bufusage;
 
-		bufusage = pgBufferUsage;
+		bufusage_start = pgBufferUsage;
 		INSTR_TIME_SET_CURRENT(start);
 
 		nested_level++;
@@ -651,25 +653,29 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 
 		/* calc differences of buffer counters. */
 		bufusage.shared_blks_hit =
-			pgBufferUsage.shared_blks_hit - bufusage.shared_blks_hit;
+			pgBufferUsage.shared_blks_hit - bufusage_start.shared_blks_hit;
 		bufusage.shared_blks_read =
-			pgBufferUsage.shared_blks_read - bufusage.shared_blks_read;
+			pgBufferUsage.shared_blks_read - bufusage_start.shared_blks_read;
 		bufusage.shared_blks_dirtied =
-			pgBufferUsage.shared_blks_dirtied - bufusage.shared_blks_dirtied;
+			pgBufferUsage.shared_blks_dirtied - bufusage_start.shared_blks_dirtied;
 		bufusage.shared_blks_written =
-			pgBufferUsage.shared_blks_written - bufusage.shared_blks_written;
+			pgBufferUsage.shared_blks_written - bufusage_start.shared_blks_written;
 		bufusage.local_blks_hit =
-			pgBufferUsage.local_blks_hit - bufusage.local_blks_hit;
+			pgBufferUsage.local_blks_hit - bufusage_start.local_blks_hit;
 		bufusage.local_blks_read =
-			pgBufferUsage.local_blks_read - bufusage.local_blks_read;
+			pgBufferUsage.local_blks_read - bufusage_start.local_blks_read;
 		bufusage.local_blks_dirtied =
-			pgBufferUsage.local_blks_dirtied - bufusage.local_blks_dirtied;
+			pgBufferUsage.local_blks_dirtied - bufusage_start.local_blks_dirtied;
 		bufusage.local_blks_written =
-			pgBufferUsage.local_blks_written - bufusage.local_blks_written;
+			pgBufferUsage.local_blks_written - bufusage_start.local_blks_written;
 		bufusage.temp_blks_read =
-			pgBufferUsage.temp_blks_read - bufusage.temp_blks_read;
+			pgBufferUsage.temp_blks_read - bufusage_start.temp_blks_read;
 		bufusage.temp_blks_written =
-			pgBufferUsage.temp_blks_written - bufusage.temp_blks_written;
+			pgBufferUsage.temp_blks_written - bufusage_start.temp_blks_written;
+		bufusage.time_read = pgBufferUsage.time_read;
+		INSTR_TIME_SUBTRACT(bufusage.time_read, bufusage_start.time_read);
+		bufusage.time_write = pgBufferUsage.time_write;
+		INSTR_TIME_SUBTRACT(bufusage.time_write, bufusage_start.time_write);
 
 		pgss_store(queryString, INSTR_TIME_GET_DOUBLE(duration), rows,
 				   &bufusage);
@@ -780,6 +786,8 @@ pgss_store(const char *query, double total_time, uint64 rows,
 		e->counters.local_blks_written += bufusage->local_blks_written;
 		e->counters.temp_blks_read += bufusage->temp_blks_read;
 		e->counters.temp_blks_written += bufusage->temp_blks_written;
+		e->counters.time_read +=  INSTR_TIME_GET_DOUBLE(bufusage->time_read);
+		e->counters.time_write += INSTR_TIME_GET_DOUBLE(bufusage->time_write);
 		e->counters.usage += usage;
 		SpinLockRelease(&e->mutex);
 	}
@@ -802,7 +810,7 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 }
 
 #define PG_STAT_STATEMENTS_COLS_V1_0	14
-#define PG_STAT_STATEMENTS_COLS			16
+#define PG_STAT_STATEMENTS_COLS			18
 
 /*
  * Retrieve statement statistics.
@@ -819,7 +827,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	bool		is_superuser = superuser();
 	HASH_SEQ_STATUS hash_seq;
 	pgssEntry  *entry;
-	bool		sql_supports_dirty_counters = true;
+	bool		sql_supports_v1_1_counters = true;
 
 	if (!pgss || !pgss_hash)
 		ereport(ERROR,
@@ -841,7 +849,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 	if (tupdesc->natts == PG_STAT_STATEMENTS_COLS_V1_0)
-		sql_supports_dirty_counters = false;
+		sql_supports_v1_1_counters = false;
 
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
@@ -899,18 +907,22 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 		values[i++] = Int64GetDatumFast(tmp.rows);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
-		if (sql_supports_dirty_counters)
+		if (sql_supports_v1_1_counters)
 			values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_read);
-		if (sql_supports_dirty_counters)
+		if (sql_supports_v1_1_counters)
 			values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
+		if (sql_supports_v1_1_counters) {
+			values[i++] = Float8GetDatumFast(tmp.time_read);
+			values[i++] = Float8GetDatumFast(tmp.time_write);
+		}
 
-		Assert(i == sql_supports_dirty_counters ? \
+		Assert(i == sql_supports_v1_1_counters ? \
 			PG_STAT_STATEMENTS_COLS : PG_STAT_STATEMENTS_COLS_V1_0);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml
index ab34ca1..f9da247 100644
--- a/doc/src/sgml/pgstatstatements.sgml
+++ b/doc/src/sgml/pgstatstatements.sgml
@@ -155,6 +155,20 @@
       <entry>Total number of temp blocks writes by the statement</entry>
      </row>
 
+     <row>
+      <entry><structfield>time_read</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for reading blocks, in seconds</entry>
+     </row>
+
+     <row>
+      <entry><structfield>time_write</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for writing out dirty blocks, in seconds</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3e17875..97e8e51 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4284,6 +4284,25 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-track-iotiming" xreflabel="track_iotiming">
+      <term><varname>track_iotiming</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>track_iotiming</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Enables timing of database I/O calls.
+        This parameter is off by default, because it may cause significant
+        overhead if the platform doesn't support fast timing information.
+        Only superusers can change this setting.
+       </para>
+       <para>
+        You can use the <xref linkend="pgtesttiming"> tool to find out the
+        overhead of timing on your system.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-track-functions" xreflabel="track_functions">
       <term><varname>track_functions</varname> (<type>enum</type>)</term>
       <indexterm>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 840e54a..ba69382 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -116,7 +116,8 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    <productname>PostgreSQL</productname>'s <firstterm>statistics collector</>
    is a subsystem that supports collection and reporting of information about
    server activity.  Presently, the collector can count accesses to tables
-   and indexes in both disk-block and individual-row terms.  It also tracks
+   and indexes in both disk-block and individual-row terms and time disk-block
+   accesses.  It also tracks
    the total number of rows in each table, and information about vacuum and
    analyze actions for each table.  It can also count calls to user-defined
    functions and the total time spent in each one.
@@ -145,6 +146,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   </para>
 
   <para>
+   The parameter <xref linkend="guc-track-iotiming"> enables timing of I/O
+   requests.
+  </para>
+
+  <para>
    The parameter <xref linkend="guc-track-functions"> enables tracking of
    usage of user-defined functions.
   </para>
@@ -483,7 +489,10 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    handles disk I/O, data that is not in the
    <productname>PostgreSQL</> buffer cache might still reside in the
    kernel's I/O cache, and might therefore still be fetched without
-   requiring a physical read. Users interested in obtaining more
+   requiring a physical read.
+   Timing info shows how much user queries were delayed by buffer reads
+   in aggregate.
+   Users interested in obtaining more
    detailed information on <productname>PostgreSQL</> I/O behavior are
    advised to use the <productname>PostgreSQL</> statistics collector
    in combination with operating system utilities that allow insight
@@ -885,6 +894,14 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      the <function>pg_stat_get_db_blocks_hit</function> function.</entry>
     </row>
     <row>
+     <entry>blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     in this database, in microseconds.
+     This value can also be returned by directly calling
+     the <function>pg_stat_get_db_blocks_time</function> function.</entry>
+    </row>
+    <row>
      <entry>tup_returned</entry>
      <entry><type>bigint</></entry>
      <entry>The number of rows returned by queries in this database.
@@ -1441,6 +1458,14 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      the <function>pg_stat_get_blocks_hit</function> function.</entry>
     </row>
     <row>
+     <entry>heap_blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     from this table, in microseconds.
+     This value can also be returned by directly calling
+     the <function>pg_stat_get_blocks_time</function> function.</entry>
+    </row>
+    <row>
      <entry>idx_blks_read</entry>
      <entry><type>name</></entry>
      <entry>Number of disk blocks read from all indexes on this table</entry>
@@ -1451,6 +1476,12 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      <entry>Number of buffer hits in all indexes of this table.</entry>
     </row>
     <row>
+     <entry>idx_blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     from all indexes on this table, in microseconds.</entry>
+    </row>
+    <row>
      <entry>toast_blks_read</entry>
      <entry><type>name</></entry>
      <entry>Number of disk blocks read from this table's TOAST table (if any)</entry>
@@ -1461,6 +1492,12 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      <entry>Number of buffer hits in this table's TOAST table (if any)</entry>
     </row>
     <row>
+     <entry>toast_blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     from this table's TOAST table (if any), in microseconds.</entry>
+    </row>
+    <row>
      <entry>tidx_blks_read</entry>
      <entry><type>name</></entry>
      <entry>Number of disk blocks read from this table's TOAST table index (if any)</entry>
@@ -1470,6 +1507,12 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      <entry><type>name</></entry>
      <entry>Number of buffer hits in this table's TOAST table index (if any)</entry>
     </row>
+    <row>
+     <entry>tidx_blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     from this table's TOAST table index (if any), in microseconds.</entry>
+    </row>
    </tbody>
    </tgroup>
   </table>
@@ -1536,6 +1579,14 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      This value can also be returned by directly calling
      the <function>pg_stat_get_blocks_hit</function> function.</entry>
     </row>
+    <row>
+     <entry>idx_blks_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Total time spent waiting for disk blocks to be read
+     from the index, in microseconds.
+     This value can also be returned by directly calling
+     the <function>pg_stat_get_blocks_time</function> function.</entry>
+    </row>
    </tbody>
    </tgroup>
   </table>
@@ -1703,6 +1754,14 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
       </entry>
      </row>
 
+     <row>
+      <entry><literal><function>pg_stat_get_xact_blocks_time</function>(<type>oid</type>)</literal></entry>
+      <entry><type>bigint</type></entry>
+      <entry>
+       Total time spent waiting for disk block requests for table or index, in the current transaction,
+       in microseconds.
+      </entry>
+     </row>
 
      <row>
       <entry><literal><function>pg_stat_get_wal_senders()</function></literal></entry>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index ab594eb..430bea1 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -440,15 +440,19 @@ CREATE VIEW pg_statio_all_tables AS
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS heap_blks_read,
             pg_stat_get_blocks_hit(C.oid) AS heap_blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS heap_blks_time,
             sum(pg_stat_get_blocks_fetched(I.indexrelid) -
                     pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_read,
             sum(pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_hit,
+            sum(pg_stat_get_blocks_time(I.indexrelid))::bigint AS idx_blks_time,
             pg_stat_get_blocks_fetched(T.oid) -
                     pg_stat_get_blocks_hit(T.oid) AS toast_blks_read,
             pg_stat_get_blocks_hit(T.oid) AS toast_blks_hit,
+            pg_stat_get_blocks_time(T.oid) AS toast_blks_time,
             pg_stat_get_blocks_fetched(X.oid) -
                     pg_stat_get_blocks_hit(X.oid) AS tidx_blks_read,
-            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit
+            pg_stat_get_blocks_hit(X.oid) AS tidx_blks_hit,
+            pg_stat_get_blocks_time(X.oid) AS tidx_blks_time
     FROM pg_class C LEFT JOIN
             pg_index I ON C.oid = I.indrelid LEFT JOIN
             pg_class T ON C.reltoastrelid = T.oid LEFT JOIN
@@ -502,7 +506,8 @@ CREATE VIEW pg_statio_all_indexes AS
             I.relname AS indexrelname,
             pg_stat_get_blocks_fetched(I.oid) -
                     pg_stat_get_blocks_hit(I.oid) AS idx_blks_read,
-            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit
+            pg_stat_get_blocks_hit(I.oid) AS idx_blks_hit,
+            pg_stat_get_blocks_time(I.oid) AS idx_blks_time
     FROM pg_class C JOIN
             pg_index X ON C.oid = X.indrelid JOIN
             pg_class I ON I.oid = X.indexrelid
@@ -526,7 +531,8 @@ CREATE VIEW pg_statio_all_sequences AS
             C.relname AS relname,
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS blks_read,
-            pg_stat_get_blocks_hit(C.oid) AS blks_hit
+            pg_stat_get_blocks_hit(C.oid) AS blks_hit,
+            pg_stat_get_blocks_time(C.oid) AS blks_time
     FROM pg_class C
             LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
     WHERE C.relkind = 'S';
@@ -595,6 +601,7 @@ CREATE VIEW pg_stat_database AS
             pg_stat_get_db_blocks_fetched(D.oid) -
                     pg_stat_get_db_blocks_hit(D.oid) AS blks_read,
             pg_stat_get_db_blocks_hit(D.oid) AS blks_hit,
+            pg_stat_get_db_blocks_time(D.oid) AS blks_time,
             pg_stat_get_db_tuples_returned(D.oid) AS tup_returned,
             pg_stat_get_db_tuples_fetched(D.oid) AS tup_fetched,
             pg_stat_get_db_tuples_inserted(D.oid) AS tup_inserted,
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index a14cae1..3707f7e 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -1236,9 +1236,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 									 usage->local_blks_written > 0);
 			bool		has_temp = (usage->temp_blks_read > 0 ||
 									usage->temp_blks_written > 0);
+			bool		has_timing = (!INSTR_TIME_IS_ZERO(usage->time_read) ||
+									  !INSTR_TIME_IS_ZERO(usage->time_write));
 
 			/* Show only positive counter values. */
-			if (has_shared || has_local || has_temp)
+			if (has_shared || has_local || has_temp || has_timing)
 			{
 				appendStringInfoSpaces(es->str, es->indent * 2);
 				appendStringInfoString(es->str, "Buffers:");
@@ -1289,6 +1291,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 						appendStringInfo(es->str, " written=%ld",
 										 usage->temp_blks_written);
 				}
+				if (has_timing)
+				{
+					appendStringInfoString(es->str, " timing");
+					if (!INSTR_TIME_IS_ZERO(usage->time_read)) {
+						appendStringInfo(es->str, " read=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_read));
+					}
+					if (!INSTR_TIME_IS_ZERO(usage->time_write)) {
+						appendStringInfo(es->str, " write=%0.2f",
+										 INSTR_TIME_GET_MILLISEC(usage->time_write));
+					}
+				}
 				appendStringInfoChar(es->str, '\n');
 			}
 		}
@@ -1304,6 +1318,8 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			ExplainPropertyLong("Local Written Blocks", usage->local_blks_written, es);
 			ExplainPropertyLong("Temp Read Blocks", usage->temp_blks_read, es);
 			ExplainPropertyLong("Temp Written Blocks", usage->temp_blks_written, es);
+			ExplainPropertyFloat("Read Waits", INSTR_TIME_GET_MILLISEC(usage->time_read), 3, es);
+			ExplainPropertyFloat("Write Waits", INSTR_TIME_GET_MILLISEC(usage->time_write), 3, es);
 		}
 	}
 
diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c
index 6e9f450..92e56d1 100644
--- a/src/backend/executor/instrument.c
+++ b/src/backend/executor/instrument.c
@@ -145,4 +145,6 @@ BufferUsageAccumDiff(BufferUsage *dst,
 	dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
 	dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
 	dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
+	INSTR_TIME_ACCUM_DIFF(dst->time_read, add->time_read, sub->time_read);
+	INSTR_TIME_ACCUM_DIFF(dst->time_write, add->time_write, sub->time_write);
 }
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index a53fc52..e9f6a3b 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3338,6 +3338,7 @@ pgstat_get_db_entry(Oid databaseid, bool create)
 		result->n_xact_rollback = 0;
 		result->n_blocks_fetched = 0;
 		result->n_blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->n_tuples_returned = 0;
 		result->n_tuples_fetched = 0;
 		result->n_tuples_inserted = 0;
@@ -3412,6 +3413,7 @@ pgstat_get_tab_entry(PgStat_StatDBEntry *dbentry, Oid tableoid, bool create)
 		result->changes_since_analyze = 0;
 		result->blocks_fetched = 0;
 		result->blocks_hit = 0;
+		INSTR_TIME_SET_ZERO(result->blocks_time);
 		result->vacuum_timestamp = 0;
 		result->vacuum_count = 0;
 		result->autovac_vacuum_timestamp = 0;
@@ -4100,6 +4102,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze = tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched = tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit = tabmsg->t_counts.t_blocks_hit;
+			tabentry->blocks_time = tabmsg->t_counts.t_blocks_time;
 
 			tabentry->vacuum_timestamp = 0;
 			tabentry->vacuum_count = 0;
@@ -4127,6 +4130,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 			tabentry->changes_since_analyze += tabmsg->t_counts.t_changed_tuples;
 			tabentry->blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 			tabentry->blocks_hit += tabmsg->t_counts.t_blocks_hit;
+			INSTR_TIME_ADD(tabentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 		}
 
 		/* Clamp n_live_tuples in case of negative delta_live_tuples */
@@ -4144,6 +4148,7 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 		dbentry->n_tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
 		dbentry->n_blocks_fetched += tabmsg->t_counts.t_blocks_fetched;
 		dbentry->n_blocks_hit += tabmsg->t_counts.t_blocks_hit;
+		INSTR_TIME_ADD(dbentry->blocks_time, tabmsg->t_counts.t_blocks_time);
 	}
 }
 
@@ -4257,6 +4262,7 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 	dbentry->n_xact_rollback = 0;
 	dbentry->n_blocks_fetched = 0;
 	dbentry->n_blocks_hit = 0;
+	INSTR_TIME_SET_ZERO(dbentry->blocks_time);
 	dbentry->n_tuples_returned = 0;
 	dbentry->n_tuples_fetched = 0;
 	dbentry->n_tuples_inserted = 0;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 3924a51..a28d8e3 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -67,6 +67,7 @@
 bool		zero_damaged_pages = false;
 int			bgwriter_lru_maxpages = 100;
 double		bgwriter_lru_multiplier = 2.0;
+bool		track_iotiming = false;
 
 /*
  * How many buffers PrefetchBuffer callers should try to stay ahead of their
@@ -86,7 +87,7 @@ static volatile BufferDesc *PinCountWaitBuf = NULL;
 static Buffer ReadBuffer_common(SMgrRelation reln, char relpersistence,
 				  ForkNumber forkNum, BlockNumber blockNum,
 				  ReadBufferMode mode, BufferAccessStrategy strategy,
-				  bool *hit);
+				  bool *hit, instr_time *io_time);
 static bool PinBuffer(volatile BufferDesc *buf, BufferAccessStrategy strategy);
 static void PinBuffer_Locked(volatile BufferDesc *buf);
 static void UnpinBuffer(volatile BufferDesc *buf, bool fixOwner);
@@ -224,6 +225,7 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 				   ReadBufferMode mode, BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 	Buffer		buf;
 
 	/* Open it at the smgr level if not already done */
@@ -245,9 +247,11 @@ ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 	 */
 	pgstat_count_buffer_read(reln);
 	buf = ReadBuffer_common(reln->rd_smgr, reln->rd_rel->relpersistence,
-							forkNum, blockNum, mode, strategy, &hit);
+							forkNum, blockNum, mode, strategy, &hit, &io_time);
 	if (hit)
 		pgstat_count_buffer_hit(reln);
+	else
+		pgstat_count_buffer_time(reln, io_time);
 	return buf;
 }
 
@@ -267,11 +271,12 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
 						  BufferAccessStrategy strategy)
 {
 	bool		hit;
+	instr_time	io_time;
 
 	SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
 
 	return ReadBuffer_common(smgr, RELPERSISTENCE_PERMANENT, forkNum, blockNum,
-							 mode, strategy, &hit);
+							 mode, strategy, &hit, &io_time);
 }
 
 
@@ -279,19 +284,22 @@ ReadBufferWithoutRelcache(RelFileNode rnode, ForkNumber forkNum,
  * ReadBuffer_common -- common logic for all ReadBuffer variants
  *
  * *hit is set to true if the request was satisfied from shared buffer cache.
+ * If track_iotiming is enabled, *io_time is set to the time the read took.
  */
 static Buffer
 ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 				  BlockNumber blockNum, ReadBufferMode mode,
-				  BufferAccessStrategy strategy, bool *hit)
+				  BufferAccessStrategy strategy, bool *hit, instr_time *io_time)
 {
 	volatile BufferDesc *bufHdr;
 	Block		bufBlock;
 	bool		found;
 	bool		isExtend;
 	bool		isLocalBuf = SmgrIsTemp(smgr);
+	instr_time io_start, io_end;
 
 	*hit = false;
+	INSTR_TIME_SET_ZERO(*io_time);
 
 	/* Make sure we will have room to remember the buffer pin */
 	ResourceOwnerEnlargeBuffers(CurrentResourceOwner);
@@ -437,8 +445,18 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
 			MemSet((char *) bufBlock, 0, BLCKSZ);
 		else
 		{
+			if (track_iotiming)
+				INSTR_TIME_SET_CURRENT(io_start);
+
 			smgrread(smgr, forkNum, blockNum, (char *) bufBlock);
 
+			if (track_iotiming)
+			{
+				INSTR_TIME_SET_CURRENT(io_end);
+				INSTR_TIME_ACCUM_DIFF(*io_time, io_end, io_start);
+				INSTR_TIME_ADD(pgBufferUsage.time_read, *io_time);
+			}
+
 			/* check for garbage data */
 			if (!PageHeaderIsValid((PageHeader) bufBlock))
 			{
@@ -1874,6 +1892,7 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 {
 	XLogRecPtr	recptr;
 	ErrorContextCallback errcontext;
+	instr_time io_start, io_end;
 
 	/*
 	 * Acquire the buffer's io_in_progress lock.  If StartBufferIO returns
@@ -1921,12 +1940,21 @@ FlushBuffer(volatile BufferDesc *buf, SMgrRelation reln)
 	buf->flags &= ~BM_JUST_DIRTIED;
 	UnlockBufHdr(buf);
 
+	if (track_iotiming)
+		INSTR_TIME_SET_CURRENT(io_start);
+
 	smgrwrite(reln,
 			  buf->tag.forkNum,
 			  buf->tag.blockNum,
 			  (char *) BufHdrGetBlock(buf),
 			  false);
 
+	if (track_iotiming)
+	{
+		INSTR_TIME_SET_CURRENT(io_end);
+		INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_write, io_end, io_start);
+	}
+
 	pgBufferUsage.shared_blks_written++;
 
 	/*
@@ -2670,6 +2698,7 @@ WaitIO(volatile BufferDesc *buf)
 static bool
 StartBufferIO(volatile BufferDesc *buf, bool forInput)
 {
+	instr_time wait_start, wait_end;
 	Assert(!InProgressBuf);
 
 	for (;;)
@@ -2678,7 +2707,28 @@ StartBufferIO(volatile BufferDesc *buf, bool forInput)
 		 * Grab the io_in_progress lock so that other processes can wait for
 		 * me to finish the I/O.
 		 */
-		LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		if (forInput && track_iotiming) {
+			/*
+			 * We need to time the lock wait to account for I/O waits where
+			 * someone else is doing the work for us. Conditional acquire
+			 * avoids double timing overhead when we do the I/O ourselves.
+			 */
+			if (!LWLockConditionalAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE)) {
+				INSTR_TIME_SET_CURRENT(wait_start);
+
+				LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+
+				/*
+				 * Only do backend local accounting, stats collector will get the
+				 * wait from the backend doing the I/O.
+				 */
+				INSTR_TIME_SET_CURRENT(wait_end);
+				INSTR_TIME_ACCUM_DIFF(pgBufferUsage.time_read, wait_end, wait_start);
+			}
+		} else {
+			LWLockAcquire(buf->io_in_progress_lock, LW_EXCLUSIVE);
+		}
+
 
 		LockBufHdr(buf);
 
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 68b2527..d0b6c57 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -22,6 +22,7 @@
 #include "utils/builtins.h"
 #include "utils/inet.h"
 #include "utils/timestamp.h"
+#include "portability/instr_time.h"
 
 /* bogus ... these externs should be in a header file */
 extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
@@ -35,6 +36,7 @@ extern Datum pg_stat_get_live_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_dead_tuples(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_autovacuum_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_last_analyze_time(PG_FUNCTION_ARGS);
@@ -67,6 +69,7 @@ extern Datum pg_stat_get_db_xact_commit(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_xact_rollback(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_db_tuples_inserted(PG_FUNCTION_ARGS);
@@ -102,6 +105,7 @@ extern Datum pg_stat_get_xact_tuples_deleted(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_tuples_hot_updated(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_fetched(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS);
+extern Datum pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS);
 
 extern Datum pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_xact_function_time(PG_FUNCTION_ARGS);
@@ -292,6 +296,22 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	double		result;
+	PgStat_StatTabEntry *tabentry;
+
+	if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL)
+		result = 0;
+	else
+		/* Cast overflows in about 300'000 years of io time */
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_last_vacuum_time(PG_FUNCTION_ARGS)
 {
 	Oid			relid = PG_GETARG_OID(0);
@@ -1120,6 +1140,22 @@ pg_stat_get_db_blocks_hit(PG_FUNCTION_ARGS)
 
 
 Datum
+pg_stat_get_db_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			dbid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_StatDBEntry *dbentry;
+
+	if ((dbentry = pgstat_fetch_stat_dbentry(dbid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(dbentry->blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+
+Datum
 pg_stat_get_db_tuples_returned(PG_FUNCTION_ARGS)
 {
 	Oid			dbid = PG_GETARG_OID(0);
@@ -1565,6 +1601,21 @@ pg_stat_get_xact_blocks_hit(PG_FUNCTION_ARGS)
 }
 
 Datum
+pg_stat_get_xact_blocks_time(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		result;
+	PgStat_TableStatus *tabentry;
+
+	if ((tabentry = find_tabstat_entry(relid)) == NULL)
+		result = 0;
+	else
+		result = (int64) INSTR_TIME_GET_MICROSEC(tabentry->t_counts.t_blocks_time);
+
+	PG_RETURN_INT64(result);
+}
+
+Datum
 pg_stat_get_xact_function_calls(PG_FUNCTION_ARGS)
 {
 	Oid			funcid = PG_GETARG_OID(0);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 3d2fe3e..8ea391a 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1018,6 +1018,15 @@ static struct config_bool ConfigureNamesBool[] =
 		true,
 		NULL, NULL, NULL
 	},
+	{
+		{"track_iotiming", PGC_SUSET, STATS_COLLECTOR,
+			gettext_noop("Collects timing information for database IO activity."),
+			NULL
+		},
+		&track_iotiming,
+		false,
+		NULL, NULL, NULL
+	},
 
 	{
 		{"update_process_title", PGC_SUSET, STATS_COLLECTOR,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 96da086..cbae3bf 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -424,6 +424,7 @@
 
 #track_activities = on
 #track_counts = on
+#track_iotiming = off
 #track_functions = none			# none, pl, all
 #track_activity_query_size = 1024 	# (change requires restart)
 #update_process_title = on
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 2db8489..c4ac58f 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -2680,6 +2680,12 @@ DATA(insert OID = 3063 ( pg_stat_get_buf_fsync_backend PGNSP PGUID 12 1 0 0 0 f
 DESCR("statistics: number of backend buffer writes that did their own fsync");
 DATA(insert OID = 2859 ( pg_stat_get_buf_alloc			PGNSP PGUID 12 1 0 0 0 f f f f t f s 0 0 20 "" _null_ _null_ _null_ _null_ pg_stat_get_buf_alloc _null_ _null_ _null_ ));
 DESCR("statistics: number of buffer allocations");
+DATA(insert OID = 3160 (  pg_stat_get_blocks_time		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads");
+DATA(insert OID = 3161 (  pg_stat_get_db_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_db_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads for database");
+DATA(insert OID = 3166 (  pg_stat_get_xact_blocks_time	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_xact_blocks_time _null_ _null_ _null_ ));
+DESCR("statistics: duration of block reads in current transaction");
 
 DATA(insert OID = 2978 (  pg_stat_get_function_calls		PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 20 "26" _null_ _null_ _null_ _null_ pg_stat_get_function_calls _null_ _null_ _null_ ));
 DESCR("statistics: number of function calls");
diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h
index 066f684..ad13914 100644
--- a/src/include/executor/instrument.h
+++ b/src/include/executor/instrument.h
@@ -28,6 +28,8 @@ typedef struct BufferUsage
 	long		local_blks_written;		/* # of local disk blocks written */
 	long		temp_blks_read; /* # of temp blocks read */
 	long		temp_blks_written;		/* # of temp blocks written */
+	instr_time	time_read;	/* time spent reading */
+	instr_time	time_write;	/* time spent writing */
 } BufferUsage;
 
 /* Flag bits included in InstrAlloc's instrument_options bitmask */
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 1281bd8..175b5df 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -97,6 +97,7 @@ typedef struct PgStat_TableCounts
 
 	PgStat_Counter t_blocks_fetched;
 	PgStat_Counter t_blocks_hit;
+	instr_time     t_blocks_time;
 } PgStat_TableCounts;
 
 /* Possible targets for resetting cluster-wide shared values */
@@ -522,6 +523,7 @@ typedef struct PgStat_StatDBEntry
 	PgStat_Counter n_xact_rollback;
 	PgStat_Counter n_blocks_fetched;
 	PgStat_Counter n_blocks_hit;
+	instr_time	blocks_time;
 	PgStat_Counter n_tuples_returned;
 	PgStat_Counter n_tuples_fetched;
 	PgStat_Counter n_tuples_inserted;
@@ -573,6 +575,7 @@ typedef struct PgStat_StatTabEntry
 
 	PgStat_Counter blocks_fetched;
 	PgStat_Counter blocks_hit;
+	instr_time	blocks_time;
 
 	TimestampTz vacuum_timestamp;		/* user initiated vacuum */
 	PgStat_Counter vacuum_count;
@@ -816,6 +819,13 @@ extern void pgstat_initstats(Relation rel);
 		if ((rel)->pgstat_info != NULL)								\
 			(rel)->pgstat_info->t_counts.t_blocks_hit++;			\
 	} while (0)
+#define pgstat_count_buffer_time(rel, io)							\
+	do {															\
+		if ((rel)->pgstat_info != NULL)								\
+			INSTR_TIME_ADD(											\
+				(rel)->pgstat_info->t_counts.t_blocks_time,			\
+				(io));												\
+	} while (0)
 
 extern void pgstat_count_heap_insert(Relation rel, int n);
 extern void pgstat_count_heap_update(Relation rel, bool hot);
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h
index de1bbd0..d72bad9 100644
--- a/src/include/storage/bufmgr.h
+++ b/src/include/storage/bufmgr.h
@@ -48,6 +48,7 @@ extern PGDLLIMPORT int NBuffers;
 extern bool zero_damaged_pages;
 extern int	bgwriter_lru_maxpages;
 extern double bgwriter_lru_multiplier;
+extern bool track_iotiming;
 extern int	target_prefetch_pages;
 
 /* in buf_init.c */
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index aaf0cca..ce6228c 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1296,7 +1296,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_all_indexes             | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, pg_stat_get_numscans(i.oid) AS idx_scan, pg_stat_get_tuples_returned(i.oid) AS idx_tup_read, pg_stat_get_tuples_fetched(i.oid) AS idx_tup_fetch FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
  pg_stat_all_tables              | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, pg_stat_get_numscans(c.oid) AS seq_scan, pg_stat_get_tuples_returned(c.oid) AS seq_tup_read, (sum(pg_stat_get_numscans(i.indexrelid)))::bigint AS idx_scan, ((sum(pg_stat_get_tuples_fetched(i.indexrelid)))::bigint + pg_stat_get_tuples_fetched(c.oid)) AS idx_tup_fetch, pg_stat_get_tuples_inserted(c.oid) AS n_tup_ins, pg_stat_get_tuples_updated(c.oid) AS n_tup_upd, pg_stat_get_tuples_deleted(c.oid) AS n_tup_del, pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd, pg_stat_get_live_tuples(c.oid) AS n_live_tup, pg_stat_get_dead_tuples(c.oid) AS n_dead_tup, pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum, pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum, pg_stat_get_last_analyze_time(c.oid) AS last_analyze, pg_stat_get_last_autoanalyze_time(c.oid) AS last_autoanalyze, pg_stat_get_vacuum_count(c.oid) AS vacuum_count, pg_stat_get_autovacuum_count(c.oid) AS autovacuum_count, pg_stat_get_analyze_count(c.oid) AS analyze_count, pg_stat_get_autoanalyze_count(c.oid) AS autoanalyze_count FROM ((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname;
  pg_stat_bgwriter                | SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed, pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req, pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint, pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean, pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, pg_stat_get_buf_written_backend() AS buffers_backend, pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync, pg_stat_get_buf_alloc() AS buffers_alloc, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
- pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
+ pg_stat_database                | SELECT d.oid AS datid, d.datname, pg_stat_get_db_numbackends(d.oid) AS numbackends, pg_stat_get_db_xact_commit(d.oid) AS xact_commit, pg_stat_get_db_xact_rollback(d.oid) AS xact_rollback, (pg_stat_get_db_blocks_fetched(d.oid) - pg_stat_get_db_blocks_hit(d.oid)) AS blks_read, pg_stat_get_db_blocks_hit(d.oid) AS blks_hit, pg_stat_get_db_blocks_time(d.oid) AS blks_time, pg_stat_get_db_tuples_returned(d.oid) AS tup_returned, pg_stat_get_db_tuples_fetched(d.oid) AS tup_fetched, pg_stat_get_db_tuples_inserted(d.oid) AS tup_inserted, pg_stat_get_db_tuples_updated(d.oid) AS tup_updated, pg_stat_get_db_tuples_deleted(d.oid) AS tup_deleted, pg_stat_get_db_conflict_all(d.oid) AS conflicts, pg_stat_get_db_temp_files(d.oid) AS temp_files, pg_stat_get_db_temp_bytes(d.oid) AS temp_bytes, pg_stat_get_db_deadlocks(d.oid) AS deadlocks, pg_stat_get_db_stat_reset_time(d.oid) AS stats_reset FROM pg_database d;
  pg_stat_database_conflicts      | SELECT d.oid AS datid, d.datname, pg_stat_get_db_conflict_tablespace(d.oid) AS confl_tablespace, pg_stat_get_db_conflict_lock(d.oid) AS confl_lock, pg_stat_get_db_conflict_snapshot(d.oid) AS confl_snapshot, pg_stat_get_db_conflict_bufferpin(d.oid) AS confl_bufferpin, pg_stat_get_db_conflict_startup_deadlock(d.oid) AS confl_deadlock FROM pg_database d;
  pg_stat_replication             | SELECT s.pid, s.usesysid, u.rolname AS usename, s.application_name, s.client_addr, s.client_hostname, s.client_port, s.backend_start, w.state, w.sent_location, w.write_location, w.flush_location, w.replay_location, w.sync_priority, w.sync_state FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, waiting, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port), pg_authid u, pg_stat_get_wal_senders() w(pid, state, sent_location, write_location, flush_location, replay_location, sync_priority, sync_state) WHERE ((s.usesysid = u.oid) AND (s.pid = w.pid));
  pg_stat_sys_indexes             | SELECT pg_stat_all_indexes.relid, pg_stat_all_indexes.indexrelid, pg_stat_all_indexes.schemaname, pg_stat_all_indexes.relname, pg_stat_all_indexes.indexrelname, pg_stat_all_indexes.idx_scan, pg_stat_all_indexes.idx_tup_read, pg_stat_all_indexes.idx_tup_fetch FROM pg_stat_all_indexes WHERE ((pg_stat_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_all_indexes.schemaname ~ '^pg_toast'::text));
@@ -1308,15 +1308,15 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_stat_xact_sys_tables         | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_stat_xact_all_tables.schemaname ~ '^pg_toast'::text));
  pg_stat_xact_user_functions     | SELECT p.oid AS funcid, n.nspname AS schemaname, p.proname AS funcname, pg_stat_get_xact_function_calls(p.oid) AS calls, (pg_stat_get_xact_function_time(p.oid) / 1000) AS total_time, (pg_stat_get_xact_function_self_time(p.oid) / 1000) AS self_time FROM (pg_proc p LEFT JOIN pg_namespace n ON ((n.oid = p.pronamespace))) WHERE ((p.prolang <> (12)::oid) AND (pg_stat_get_xact_function_calls(p.oid) IS NOT NULL));
  pg_stat_xact_user_tables        | SELECT pg_stat_xact_all_tables.relid, pg_stat_xact_all_tables.schemaname, pg_stat_xact_all_tables.relname, pg_stat_xact_all_tables.seq_scan, pg_stat_xact_all_tables.seq_tup_read, pg_stat_xact_all_tables.idx_scan, pg_stat_xact_all_tables.idx_tup_fetch, pg_stat_xact_all_tables.n_tup_ins, pg_stat_xact_all_tables.n_tup_upd, pg_stat_xact_all_tables.n_tup_del, pg_stat_xact_all_tables.n_tup_hot_upd FROM pg_stat_xact_all_tables WHERE ((pg_stat_xact_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_stat_xact_all_tables.schemaname !~ '^pg_toast'::text));
- pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
- pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
- pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
- pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
- pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
- pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
- pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
- pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
+ pg_statio_all_indexes           | SELECT c.oid AS relid, i.oid AS indexrelid, n.nspname AS schemaname, c.relname, i.relname AS indexrelname, (pg_stat_get_blocks_fetched(i.oid) - pg_stat_get_blocks_hit(i.oid)) AS idx_blks_read, pg_stat_get_blocks_hit(i.oid) AS idx_blks_hit, pg_stat_get_blocks_time(i.oid) AS idx_blks_time FROM (((pg_class c JOIN pg_index x ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"]));
+ pg_statio_all_sequences         | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS blks_read, pg_stat_get_blocks_hit(c.oid) AS blks_hit, pg_stat_get_blocks_time(c.oid) AS blks_time FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'S'::"char");
+ pg_statio_all_tables            | SELECT c.oid AS relid, n.nspname AS schemaname, c.relname, (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read, pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit, pg_stat_get_blocks_time(c.oid) AS heap_blks_time, (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read, (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit, (sum(pg_stat_get_blocks_time(i.indexrelid)))::bigint AS idx_blks_time, (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read, pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit, pg_stat_get_blocks_time(t.oid) AS toast_blks_time, (pg_stat_get_blocks_fetched(x.oid) - pg_stat_get_blocks_hit(x.oid)) AS tidx_blks_read, pg_stat_get_blocks_hit(x.oid) AS tidx_blks_hit, pg_stat_get_blocks_time(x.oid) AS tidx_blks_time FROM ((((pg_class c LEFT JOIN pg_index i ON ((c.oid = i.indrelid))) LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid))) LEFT JOIN pg_class x ON ((t.reltoastidxid = x.oid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char"])) GROUP BY c.oid, n.nspname, c.relname, t.oid, x.oid;
+ pg_statio_sys_indexes           | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_indexes.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_sequences         | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_sequences.schemaname ~ '^pg_toast'::text));
+ pg_statio_sys_tables            | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname = ANY (ARRAY['pg_catalog'::name, 'information_schema'::name])) OR (pg_statio_all_tables.schemaname ~ '^pg_toast'::text));
+ pg_statio_user_indexes          | SELECT pg_statio_all_indexes.relid, pg_statio_all_indexes.indexrelid, pg_statio_all_indexes.schemaname, pg_statio_all_indexes.relname, pg_statio_all_indexes.indexrelname, pg_statio_all_indexes.idx_blks_read, pg_statio_all_indexes.idx_blks_hit, pg_statio_all_indexes.idx_blks_time FROM pg_statio_all_indexes WHERE ((pg_statio_all_indexes.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_indexes.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_sequences        | SELECT pg_statio_all_sequences.relid, pg_statio_all_sequences.schemaname, pg_statio_all_sequences.relname, pg_statio_all_sequences.blks_read, pg_statio_all_sequences.blks_hit, pg_statio_all_sequences.blks_time FROM pg_statio_all_sequences WHERE ((pg_statio_all_sequences.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_sequences.schemaname !~ '^pg_toast'::text));
+ pg_statio_user_tables           | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.heap_blks_time, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.idx_blks_time, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.toast_blks_time, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit, pg_statio_all_tables.tidx_blks_time FROM pg_statio_all_tables WHERE ((pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_statio_all_tables.schemaname !~ '^pg_toast'::text));
  pg_stats                        | SELECT n.nspname AS schemaname, c.relname AS tablename, a.attname, s.stainherit AS inherited, s.stanullfrac AS null_frac, s.stawidth AS avg_width, s.stadistinct AS n_distinct, CASE WHEN (s.stakind1 = 1) THEN s.stavalues1 WHEN (s.stakind2 = 1) THEN s.stavalues2 WHEN (s.stakind3 = 1) THEN s.stavalues3 WHEN (s.stakind4 = 1) THEN s.stavalues4 WHEN (s.stakind5 = 1) THEN s.stavalues5 ELSE NULL::anyarray END AS most_common_vals, CASE WHEN (s.stakind1 = 1) THEN s.stanumbers1 WHEN (s.stakind2 = 1) THEN s.stanumbers2 WHEN (s.stakind3 = 1) THEN s.stanumbers3 WHEN (s.stakind4 = 1) THEN s.stanumbers4 WHEN (s.stakind5 = 1) THEN s.stanumbers5 ELSE NULL::real[] END AS most_common_freqs, CASE WHEN (s.stakind1 = 2) THEN s.stavalues1 WHEN (s.stakind2 = 2) THEN s.stavalues2 WHEN (s.stakind3 = 2) THEN s.stavalues3 WHEN (s.stakind4 = 2) THEN s.stavalues4 WHEN (s.stakind5 = 2) THEN s.stavalues5 ELSE NULL::anyarray END AS histogram_bounds, CASE WHEN (s.stakind1 = 3) THEN s.stanumbers1[1] WHEN (s.stakind2 = 3) THEN s.stanumbers2[1] WHEN (s.stakind3 = 3) THEN s.stanumbers3[1] WHEN (s.stakind4 = 3) THEN s.stanumbers4[1] WHEN (s.stakind5 = 3) THEN s.stanumbers5[1] ELSE NULL::real END AS correlation, CASE WHEN (s.stakind1 = 4) THEN s.stavalues1 WHEN (s.stakind2 = 4) THEN s.stavalues2 WHEN (s.stakind3 = 4) THEN s.stavalues3 WHEN (s.stakind4 = 4) THEN s.stavalues4 WHEN (s.stakind5 = 4) THEN s.stavalues5 ELSE NULL::anyarray END AS most_common_elems, CASE WHEN (s.stakind1 = 4) THEN s.stanumbers1 WHEN (s.stakind2 = 4) THEN s.stanumbers2 WHEN (s.stakind3 = 4) THEN s.stanumbers3 WHEN (s.stakind4 = 4) THEN s.stanumbers4 WHEN (s.stakind5 = 4) THEN s.stanumbers5 ELSE NULL::real[] END AS most_common_elem_freqs, CASE WHEN (s.stakind1 = 5) THEN s.stanumbers1 WHEN (s.stakind2 = 5) THEN s.stanumbers2 WHEN (s.stakind3 = 5) THEN s.stanumbers3 WHEN (s.stakind4 = 5) THEN s.stanumbers4 WHEN (s.stakind5 = 5) THEN s.stanumbers5 ELSE NULL::real[] END AS elem_count_histogram FROM (((pg_statistic s JOIN pg_class c ON ((c.oid = s.starelid))) JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum)))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE ((NOT a.attisdropped) AND has_column_privilege(c.oid, a.attnum, 'select'::text));
  pg_tables                       | SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.relhastriggers AS hastriggers FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = 'r'::"char");
  pg_timezone_abbrevs             | SELECT pg_timezone_abbrevs.abbrev, pg_timezone_abbrevs.utc_offset, pg_timezone_abbrevs.is_dst FROM pg_timezone_abbrevs() pg_timezone_abbrevs(abbrev, utc_offset, is_dst);

diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
index 223271d..f976419 100644
--- a/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.0--1.1.sql
@@ -28,7 +28,9 @@ CREATE FUNCTION pg_stat_statements(
     OUT local_blks_dirtied int8,
     OUT local_blks_written int8,
     OUT temp_blks_read int8,
-    OUT temp_blks_written int8
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
 )
 RETURNS SETOF record
 AS 'MODULE_PATHNAME'
diff --git a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
index 1233736..f4bdf12 100644
--- a/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
+++ b/contrib/pg_stat_statements/pg_stat_statements--1.1.sql
@@ -25,7 +25,9 @@ CREATE FUNCTION pg_stat_statements(
     OUT local_blks_dirtied int8,
     OUT local_blks_written int8,
     OUT temp_blks_read int8,
-    OUT temp_blks_written int8
+    OUT temp_blks_written int8,
+    OUT time_read float8,
+    OUT time_write float8
 )
 RETURNS SETOF record
 AS 'MODULE_PATHNAME'
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 914fbf2..8e34740 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -85,6 +85,8 @@ typedef struct Counters
 	int64		local_blks_written;		/* # of local disk blocks written */
 	int64		temp_blks_read; /* # of temp blocks read */
 	int64		temp_blks_written;		/* # of temp blocks written */
+	double		time_read;		/* time spent reading in seconds */
+	double		time_write;		/* time spent writing in seconds */
 	double		usage;			/* usage factor */
 } Counters;
 
@@ -618,9 +620,9 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 		instr_time	start;
 		instr_time	duration;
 		uint64		rows = 0;
-		BufferUsage bufusage;
+		BufferUsage bufusage_start, bufusage;
 
-		bufusage = pgBufferUsage;
+		bufusage_start = pgBufferUsage;
 		INSTR_TIME_SET_CURRENT(start);
 
 		nested_level++;
@@ -651,25 +653,29 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 
 		/* calc differences of buffer counters. */
 		bufusage.shared_blks_hit =
-			pgBufferUsage.shared_blks_hit - bufusage.shared_blks_hit;
+			pgBufferUsage.shared_blks_hit - bufusage_start.shared_blks_hit;
 		bufusage.shared_blks_read =
-			pgBufferUsage.shared_blks_read - bufusage.shared_blks_read;
+			pgBufferUsage.shared_blks_read - bufusage_start.shared_blks_read;
 		bufusage.shared_blks_dirtied =
-			pgBufferUsage.shared_blks_dirtied - bufusage.shared_blks_dirtied;
+			pgBufferUsage.shared_blks_dirtied - bufusage_start.shared_blks_dirtied;
 		bufusage.shared_blks_written =
-			pgBufferUsage.shared_blks_written - bufusage.shared_blks_written;
+			pgBufferUsage.shared_blks_written - bufusage_start.shared_blks_written;
 		bufusage.local_blks_hit =
-			pgBufferUsage.local_blks_hit - bufusage.local_blks_hit;
+			pgBufferUsage.local_blks_hit - bufusage_start.local_blks_hit;
 		bufusage.local_blks_read =
-			pgBufferUsage.local_blks_read - bufusage.local_blks_read;
+			pgBufferUsage.local_blks_read - bufusage_start.local_blks_read;
 		bufusage.local_blks_dirtied =
-			pgBufferUsage.local_blks_dirtied - bufusage.local_blks_dirtied;
+			pgBufferUsage.local_blks_dirtied - bufusage_start.local_blks_dirtied;
 		bufusage.local_blks_written =
-			pgBufferUsage.local_blks_written - bufusage.local_blks_written;
+			pgBufferUsage.local_blks_written - bufusage_start.local_blks_written;
 		bufusage.temp_blks_read =
-			pgBufferUsage.temp_blks_read - bufusage.temp_blks_read;
+			pgBufferUsage.temp_blks_read - bufusage_start.temp_blks_read;
 		bufusage.temp_blks_written =
-			pgBufferUsage.temp_blks_written - bufusage.temp_blks_written;
+			pgBufferUsage.temp_blks_written - bufusage_start.temp_blks_written;
+		bufusage.time_read = pgBufferUsage.time_read;
+		INSTR_TIME_SUBTRACT(bufusage.time_read, bufusage_start.time_read);
+		bufusage.time_write = pgBufferUsage.time_write;
+		INSTR_TIME_SUBTRACT(bufusage.time_write, bufusage_start.time_write);
 
 		pgss_store(queryString, INSTR_TIME_GET_DOUBLE(duration), rows,
 				   &bufusage);
@@ -780,6 +786,8 @@ pgss_store(const char *query, double total_time, uint64 rows,
 		e->counters.local_blks_written += bufusage->local_blks_written;
 		e->counters.temp_blks_read += bufusage->temp_blks_read;
 		e->counters.temp_blks_written += bufusage->temp_blks_written;
+		e->counters.time_read +=  INSTR_TIME_GET_DOUBLE(bufusage->time_read);
+		e->counters.time_write += INSTR_TIME_GET_DOUBLE(bufusage->time_write);
 		e->counters.usage += usage;
 		SpinLockRelease(&e->mutex);
 	}
@@ -802,7 +810,7 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 }
 
 #define PG_STAT_STATEMENTS_COLS_V1_0	14
-#define PG_STAT_STATEMENTS_COLS			16
+#define PG_STAT_STATEMENTS_COLS			18
 
 /*
  * Retrieve statement statistics.
@@ -819,7 +827,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	bool		is_superuser = superuser();
 	HASH_SEQ_STATUS hash_seq;
 	pgssEntry  *entry;
-	bool		sql_supports_dirty_counters = true;
+	bool		sql_supports_v1_1_counters = true;
 
 	if (!pgss || !pgss_hash)
 		ereport(ERROR,
@@ -841,7 +849,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 	if (tupdesc->natts == PG_STAT_STATEMENTS_COLS_V1_0)
-		sql_supports_dirty_counters = false;
+		sql_supports_v1_1_counters = false;
 
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
@@ -899,18 +907,22 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 		values[i++] = Int64GetDatumFast(tmp.rows);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
-		if (sql_supports_dirty_counters)
+		if (sql_supports_v1_1_counters)
 			values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_read);
-		if (sql_supports_dirty_counters)
+		if (sql_supports_v1_1_counters)
 			values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
+		if (sql_supports_v1_1_counters) {
+			values[i++] = Float8GetDatumFast(tmp.time_read);
+			values[i++] = Float8GetDatumFast(tmp.time_write);
+		}
 
-		Assert(i == sql_supports_dirty_counters ? \
+		Assert(i == sql_supports_v1_1_counters ? \
 			PG_STAT_STATEMENTS_COLS : PG_STAT_STATEMENTS_COLS_V1_0);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml
index ab34ca1..f9da247 100644
--- a/doc/src/sgml/pgstatstatements.sgml
+++ b/doc/src/sgml/pgstatstatements.sgml
@@ -155,6 +155,20 @@
       <entry>Total number of temp blocks writes by the statement</entry>
      </row>
 
+     <row>
+      <entry><structfield>time_read</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for reading blocks, in seconds</entry>
+     </row>
+
+     <row>
+      <entry><structfield>time_write</structfield></entry>
+      <entry><type>double precision</type></entry>
+      <entry></entry>
+      <entry>Total time spent by the statement for writing out dirty blocks, in seconds</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>