On Fri, Jan 31, 2025 at 11:29:31AM +0300, Nazir Bilal Yavuz wrote: > On Wed, 29 Jan 2025 at 18:16, Bertrand Drouvot > <bertranddrouvot...@gmail.com> wrote: >> I think that's the main reason why ff99918c625 added this new GUC (looking at >> the commit message). I'd feel more comfortable if we keep it. > > As Michael suggested, I will run a couple of benchmarks to see the > actual effect of this change. Then let's see if this affects anything.
I've looked at bit at all that today, and something like the attached is what seems like the best streamlined version to me for the main feature. I am also planning to run some short benchmarks with track_io_timing=on on HEAD and with the patch, then see the difference, without any relationship to track_wal_io_timing. The comment additions in pgstat_count_io_op_time() were worth a patch of their own. This part has been applied as b998fedab74c, after a few tweaks of my own. -- Michael
From f3bff6e4a646cb90fd5ba0e178e282d189eda39e Mon Sep 17 00:00:00 2001
From: Nazir Bilal Yavuz <byavu...@gmail.com>
Date: Mon, 27 Jan 2025 14:03:54 +0300
Subject: [PATCH v13] Add WAL I/O stats to both pg_stat_io view and per backend
I/O statistics
This commit adds WAL I/O stats to both pg_stat_io view and per backend
I/O statistics (pg_stat_get_backend_io()).
This commit introduces a three new I/O concepts:
- IOObject IOOBJECT_WAL is used for tracking all WAL I/Os.
- IOOBJECT_WAL / IOCONTEXT_NORMAL is used for tracking I/O operations
done on already created wal segments.
- IOOBJECT_WAL / IOCONTEXT_INIT is used for tracking I/O operations done
while creating the WAL segments.
XXX: Bump catalog version.
XXX: Bump pgstats file version.
---
src/include/pgstat.h | 4 +-
src/backend/access/transam/xlog.c | 39 +++++++---
src/backend/access/transam/xlogreader.c | 10 +++
src/backend/access/transam/xlogrecovery.c | 12 ++++
src/backend/utils/activity/pgstat_backend.c | 9 +--
src/backend/utils/activity/pgstat_io.c | 79 +++++++++++++++------
src/test/regress/expected/stats.out | 53 ++++++++++++++
src/test/regress/sql/stats.sql | 25 +++++++
doc/src/sgml/monitoring.sgml | 19 ++++-
9 files changed, 212 insertions(+), 38 deletions(-)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 81ec0161c09..a61b488e8d8 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -274,14 +274,16 @@ typedef enum IOObject
{
IOOBJECT_RELATION,
IOOBJECT_TEMP_RELATION,
+ IOOBJECT_WAL,
} IOObject;
-#define IOOBJECT_NUM_TYPES (IOOBJECT_TEMP_RELATION + 1)
+#define IOOBJECT_NUM_TYPES (IOOBJECT_WAL + 1)
typedef enum IOContext
{
IOCONTEXT_BULKREAD,
IOCONTEXT_BULKWRITE,
+ IOCONTEXT_INIT,
IOCONTEXT_NORMAL,
IOCONTEXT_VACUUM,
} IOContext;
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 90ade4e7d39..eb19cf5690c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2435,16 +2435,19 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
{
errno = 0;
- /* Measure I/O timing to write WAL data */
- if (track_wal_io_timing)
- INSTR_TIME_SET_CURRENT(start);
- else
- INSTR_TIME_SET_ZERO(start);
+ /*
+ * Measure I/O timing to write WAL data, for pg_stat_wal
+ * and/or pg_stat_io.
+ */
+ start = pgstat_prepare_io_time(track_wal_io_timing || track_io_timing);
pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE);
written = pg_pwrite(openLogFile, from, nleft, startoffset);
pgstat_report_wait_end();
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL,
+ IOOP_WRITE, start, 1, written);
+
/*
* Increment the I/O timing and the number of times WAL data
* were written out to disk.
@@ -3216,6 +3219,7 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
int fd;
int save_errno;
int open_flags = O_RDWR | O_CREAT | O_EXCL | PG_BINARY;
+ instr_time io_start;
Assert(logtli != 0);
@@ -3259,6 +3263,9 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m", tmppath)));
+ /* Measure I/O timing when initializing segment */
+ io_start = pgstat_prepare_io_time(track_io_timing);
+
pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE);
save_errno = 0;
if (wal_init_zero)
@@ -3294,6 +3301,9 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
}
pgstat_report_wait_end();
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_INIT, IOOP_WRITE,
+ io_start, 1, wal_segment_size);
+
if (save_errno)
{
/*
@@ -3310,6 +3320,9 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
errmsg("could not write to file \"%s\": %m", tmppath)));
}
+ /* Measure I/O timing when flushing segment */
+ io_start = pgstat_prepare_io_time(track_io_timing);
+
pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC);
if (pg_fsync(fd) != 0)
{
@@ -3322,6 +3335,9 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
}
pgstat_report_wait_end();
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_INIT,
+ IOOP_FSYNC, io_start, 1, 0);
+
if (close(fd) != 0)
ereport(ERROR,
(errcode_for_file_access(),
@@ -8696,11 +8712,11 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
wal_sync_method == WAL_SYNC_METHOD_OPEN_DSYNC)
return;
- /* Measure I/O timing to sync the WAL file */
- if (track_wal_io_timing)
- INSTR_TIME_SET_CURRENT(start);
- else
- INSTR_TIME_SET_ZERO(start);
+ /*
+ * Measure I/O timing to sync the WAL file for pg_stat_wal and/or
+ * pg_stat_io.
+ */
+ start = pgstat_prepare_io_time(track_io_timing || track_wal_io_timing);
pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);
switch (wal_sync_method)
@@ -8757,6 +8773,9 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, end, start);
}
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_FSYNC,
+ start, 1, 0);
+
PendingWalStats.wal_sync++;
}
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 91b6a91767d..6cf5ef90be0 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -35,6 +35,7 @@
#ifndef FRONTEND
#include "pgstat.h"
+#include "storage/bufmgr.h"
#else
#include "common/logging.h"
#endif
@@ -1507,6 +1508,9 @@ WALRead(XLogReaderState *state,
char *p;
XLogRecPtr recptr;
Size nbytes;
+#ifndef FRONTEND
+ instr_time io_start;
+#endif
p = buf;
recptr = startptr;
@@ -1552,6 +1556,9 @@ WALRead(XLogReaderState *state,
segbytes = nbytes;
#ifndef FRONTEND
+ /* Measure I/O timing when reading segment */
+ io_start = pgstat_prepare_io_time(track_io_timing);
+
pgstat_report_wait_start(WAIT_EVENT_WAL_READ);
#endif
@@ -1561,6 +1568,9 @@ WALRead(XLogReaderState *state,
#ifndef FRONTEND
pgstat_report_wait_end();
+
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_READ,
+ io_start, 1, readbytes);
#endif
if (readbytes <= 0)
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index cf2b007806f..473de6710d7 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -60,6 +60,7 @@
#include "utils/datetime.h"
#include "utils/fmgrprotos.h"
#include "utils/guc_hooks.h"
+#include "utils/pgstat_internal.h"
#include "utils/pg_lsn.h"
#include "utils/ps_status.h"
#include "utils/pg_rusage.h"
@@ -3306,6 +3307,7 @@ XLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen,
uint32 targetPageOff;
XLogSegNo targetSegNo PG_USED_FOR_ASSERTS_ONLY;
int r;
+ instr_time io_start;
XLByteToSeg(targetPagePtr, targetSegNo, wal_segment_size);
targetPageOff = XLogSegmentOffset(targetPagePtr, wal_segment_size);
@@ -3398,6 +3400,9 @@ retry:
/* Read the requested page */
readOff = targetPageOff;
+ /* Measure I/O timing when reading segment */
+ io_start = pgstat_prepare_io_time(track_io_timing);
+
pgstat_report_wait_start(WAIT_EVENT_WAL_READ);
r = pg_pread(readFile, readBuf, XLOG_BLCKSZ, (off_t) readOff);
if (r != XLOG_BLCKSZ)
@@ -3406,6 +3411,10 @@ retry:
int save_errno = errno;
pgstat_report_wait_end();
+
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_READ,
+ io_start, 1, r);
+
XLogFileName(fname, curFileTLI, readSegNo, wal_segment_size);
if (r < 0)
{
@@ -3426,6 +3435,9 @@ retry:
}
pgstat_report_wait_end();
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_NORMAL, IOOP_READ,
+ io_start, 1, r);
+
Assert(targetSegNo == readSegNo);
Assert(targetPageOff == readOff);
Assert(reqLen <= readLen);
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bcf9e4b1487..338da73a9a9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -24,6 +24,7 @@
#include "postgres.h"
+#include "access/xlog.h"
#include "storage/bufmgr.h"
#include "utils/memutils.h"
#include "utils/pgstat_internal.h"
@@ -43,7 +44,7 @@ void
pgstat_count_backend_io_op_time(IOObject io_object, IOContext io_context,
IOOp io_op, instr_time io_time)
{
- Assert(track_io_timing);
+ Assert(track_io_timing || track_wal_io_timing);
if (!pgstat_tracks_backend_bktype(MyBackendType))
return;
@@ -236,9 +237,6 @@ pgstat_tracks_backend_bktype(BackendType bktype)
case B_DEAD_END_BACKEND:
case B_ARCHIVER:
case B_LOGGER:
- case B_WAL_RECEIVER:
- case B_WAL_WRITER:
- case B_WAL_SUMMARIZER:
case B_BG_WRITER:
case B_CHECKPOINTER:
case B_STARTUP:
@@ -249,7 +247,10 @@ pgstat_tracks_backend_bktype(BackendType bktype)
case B_BG_WORKER:
case B_STANDALONE_BACKEND:
case B_SLOTSYNC_WORKER:
+ case B_WAL_RECEIVER:
case B_WAL_SENDER:
+ case B_WAL_SUMMARIZER:
+ case B_WAL_WRITER:
return true;
}
diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c
index 7aee6a396f2..28a431084b8 100644
--- a/src/backend/utils/activity/pgstat_io.c
+++ b/src/backend/utils/activity/pgstat_io.c
@@ -127,21 +127,24 @@ pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
INSTR_TIME_SET_CURRENT(io_time);
INSTR_TIME_SUBTRACT(io_time, start_time);
- if (io_op == IOOP_WRITE || io_op == IOOP_EXTEND)
+ if (io_object != IOOBJECT_WAL)
{
- pgstat_count_buffer_write_time(INSTR_TIME_GET_MICROSEC(io_time));
- if (io_object == IOOBJECT_RELATION)
- INSTR_TIME_ADD(pgBufferUsage.shared_blk_write_time, io_time);
- else if (io_object == IOOBJECT_TEMP_RELATION)
- INSTR_TIME_ADD(pgBufferUsage.local_blk_write_time, io_time);
- }
- else if (io_op == IOOP_READ)
- {
- pgstat_count_buffer_read_time(INSTR_TIME_GET_MICROSEC(io_time));
- if (io_object == IOOBJECT_RELATION)
- INSTR_TIME_ADD(pgBufferUsage.shared_blk_read_time, io_time);
- else if (io_object == IOOBJECT_TEMP_RELATION)
- INSTR_TIME_ADD(pgBufferUsage.local_blk_read_time, io_time);
+ if (io_op == IOOP_WRITE || io_op == IOOP_EXTEND)
+ {
+ pgstat_count_buffer_write_time(INSTR_TIME_GET_MICROSEC(io_time));
+ if (io_object == IOOBJECT_RELATION)
+ INSTR_TIME_ADD(pgBufferUsage.shared_blk_write_time, io_time);
+ else if (io_object == IOOBJECT_TEMP_RELATION)
+ INSTR_TIME_ADD(pgBufferUsage.local_blk_write_time, io_time);
+ }
+ else if (io_op == IOOP_READ)
+ {
+ pgstat_count_buffer_read_time(INSTR_TIME_GET_MICROSEC(io_time));
+ if (io_object == IOOBJECT_RELATION)
+ INSTR_TIME_ADD(pgBufferUsage.shared_blk_read_time, io_time);
+ else if (io_object == IOOBJECT_TEMP_RELATION)
+ INSTR_TIME_ADD(pgBufferUsage.local_blk_read_time, io_time);
+ }
}
INSTR_TIME_ADD(PendingIOStats.pending_times[io_object][io_context][io_op],
@@ -249,6 +252,8 @@ pgstat_get_io_context_name(IOContext io_context)
return "bulkread";
case IOCONTEXT_BULKWRITE:
return "bulkwrite";
+ case IOCONTEXT_INIT:
+ return "init";
case IOCONTEXT_NORMAL:
return "normal";
case IOCONTEXT_VACUUM:
@@ -268,6 +273,8 @@ pgstat_get_io_object_name(IOObject io_object)
return "relation";
case IOOBJECT_TEMP_RELATION:
return "temp relation";
+ case IOOBJECT_WAL:
+ return "wal";
}
elog(ERROR, "unrecognized IOObject value: %d", io_object);
@@ -340,8 +347,6 @@ pgstat_io_snapshot_cb(void)
* - Syslogger because it is not connected to shared memory
* - Archiver because most relevant archiving IO is delegated to a
* specialized command or module
-* - WAL Receiver, WAL Writer, and WAL Summarizer IO are not tracked in
-* pg_stat_io for now
*
* Function returns true if BackendType participates in the cumulative stats
* subsystem for IO and false if it does not.
@@ -362,9 +367,6 @@ pgstat_tracks_io_bktype(BackendType bktype)
case B_DEAD_END_BACKEND:
case B_ARCHIVER:
case B_LOGGER:
- case B_WAL_RECEIVER:
- case B_WAL_WRITER:
- case B_WAL_SUMMARIZER:
return false;
case B_AUTOVAC_LAUNCHER:
@@ -376,7 +378,10 @@ pgstat_tracks_io_bktype(BackendType bktype)
case B_SLOTSYNC_WORKER:
case B_STANDALONE_BACKEND:
case B_STARTUP:
+ case B_WAL_RECEIVER:
case B_WAL_SENDER:
+ case B_WAL_SUMMARIZER:
+ case B_WAL_WRITER:
return true;
}
@@ -402,6 +407,15 @@ pgstat_tracks_io_object(BackendType bktype, IOObject io_object,
if (!pgstat_tracks_io_bktype(bktype))
return false;
+ /*
+ * Currently, IO on IOOBJECT_WAL objects can only occur in the
+ * IOCONTEXT_NORMAL and IOCONTEXT_INIT IOContexts.
+ */
+ if (io_object == IOOBJECT_WAL &&
+ (io_context != IOCONTEXT_NORMAL &&
+ io_context != IOCONTEXT_INIT))
+ return false;
+
/*
* Currently, IO on temporary relations can only occur in the
* IOCONTEXT_NORMAL IOContext.
@@ -468,14 +482,28 @@ pgstat_tracks_io_op(BackendType bktype, IOObject io_object,
/*
* Some BackendTypes will not do certain IOOps.
*/
- if ((bktype == B_BG_WRITER || bktype == B_CHECKPOINTER) &&
+ if (bktype == B_BG_WRITER &&
(io_op == IOOP_READ || io_op == IOOP_EVICT || io_op == IOOP_HIT))
return false;
+ if (bktype == B_CHECKPOINTER &&
+ ((io_object != IOOBJECT_WAL && io_op == IOOP_READ) ||
+ (io_op == IOOP_EVICT || io_op == IOOP_HIT)))
+ return false;
+
if ((bktype == B_AUTOVAC_LAUNCHER || bktype == B_BG_WRITER ||
bktype == B_CHECKPOINTER) && io_op == IOOP_EXTEND)
return false;
+ /*
+ * Some BackendTypes do not perform reads with IOOBJECT_WAL.
+ */
+ if (io_object == IOOBJECT_WAL && io_op == IOOP_READ &&
+ (bktype == B_WAL_RECEIVER || bktype == B_BG_WRITER ||
+ bktype == B_AUTOVAC_WORKER || bktype == B_AUTOVAC_WORKER ||
+ bktype == B_WAL_WRITER))
+ return false;
+
/*
* Temporary tables are not logged and thus do not require fsync'ing.
* Writeback is not requested for temporary tables.
@@ -500,6 +528,17 @@ pgstat_tracks_io_op(BackendType bktype, IOObject io_object,
if (!strategy_io_context && io_op == IOOP_REUSE)
return false;
+ /*
+ * IOOBJECT_WAL IOObject will not do certain IOOps depending on IOContext.
+ */
+ if (io_object == IOOBJECT_WAL && io_context == IOCONTEXT_INIT &&
+ !(io_op == IOOP_WRITE || io_op == IOOP_FSYNC))
+ return false;
+
+ if (io_object == IOOBJECT_WAL && io_context == IOCONTEXT_NORMAL &&
+ !(io_op == IOOP_WRITE || io_op == IOOP_READ || io_op == IOOP_FSYNC))
+ return false;
+
/*
* IOOP_FSYNC IOOps done by a backend using a BufferAccessStrategy are
* counted in the IOCONTEXT_NORMAL IOContext. See comment in
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index a0317b7208e..9a02481ee7e 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -862,6 +862,33 @@ WHERE pg_stat_get_backend_pid(beid) = pg_backend_pid();
t
(1 row)
+-- Test pg_stat_io for WAL in an init context, that should do writes
+-- and syncs.
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'init' AND object = 'wal' \gset io_sum_wal_init_
+SELECT :io_sum_wal_init_writes > 0;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT current_setting('fsync') = 'off'
+ OR :io_sum_wal_init_fsyncs > 0;
+ ?column?
+----------
+ t
+(1 row)
+
+-- Test pg_stat_io for WAL in a normal context, that should do reads as well.
+SELECT SUM(reads) > 0
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal';
+ ?column?
+----------
+ t
+(1 row)
+
-----
-- Test that resetting stats works for reset timestamp
-----
@@ -1256,6 +1283,7 @@ SELECT pg_stat_get_subscription_stats(NULL);
-- - extends of relations using shared buffers
-- - fsyncs done to ensure the durability of data dirtying shared buffers
-- - shared buffer hits
+-- - WAL writes and fsyncs in IOContext IOCONTEXT_NORMAL
-- There is no test for blocks evicted from shared buffers, because we cannot
-- be sure of the state of shared buffers at the point the test is run.
-- Create a regular table and insert some data to generate IOCONTEXT_NORMAL
@@ -1273,6 +1301,9 @@ SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_get_backend_io(pg_backend_pid())
WHERE object = 'relation' \gset my_io_sum_shared_before_
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal' \gset io_sum_wal_normal_before_
CREATE TABLE test_io_shared(a int);
INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
SELECT pg_stat_force_next_flush();
@@ -1335,6 +1366,28 @@ SELECT current_setting('fsync') = 'off'
t
(1 row)
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal' \gset io_sum_wal_normal_after_
+SELECT current_setting('synchronous_commit') = 'on';
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT :io_sum_wal_normal_after_writes > :io_sum_wal_normal_before_writes;
+ ?column?
+----------
+ t
+(1 row)
+
+SELECT current_setting('fsync') = 'off'
+ OR :io_sum_wal_normal_after_fsyncs > :io_sum_wal_normal_before_fsyncs;
+ ?column?
+----------
+ t
+(1 row)
+
-- Change the tablespace so that the table is rewritten directly, then SELECT
-- from it to cause it to be read back into shared buffers.
SELECT sum(reads) AS io_sum_shared_before_reads
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 399c72bbcf7..901e7bd56e3 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -442,6 +442,20 @@ SELECT (current_schemas(true))[1] = ('pg_temp_' || beid::text) AS match
FROM pg_stat_get_backend_idset() beid
WHERE pg_stat_get_backend_pid(beid) = pg_backend_pid();
+-- Test pg_stat_io for WAL in an init context, that should do writes
+-- and syncs.
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'init' AND object = 'wal' \gset io_sum_wal_init_
+SELECT :io_sum_wal_init_writes > 0;
+SELECT current_setting('fsync') = 'off'
+ OR :io_sum_wal_init_fsyncs > 0;
+
+-- Test pg_stat_io for WAL in a normal context, that should do reads as well.
+SELECT SUM(reads) > 0
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal';
+
-----
-- Test that resetting stats works for reset timestamp
-----
@@ -602,6 +616,7 @@ SELECT pg_stat_get_subscription_stats(NULL);
-- - extends of relations using shared buffers
-- - fsyncs done to ensure the durability of data dirtying shared buffers
-- - shared buffer hits
+-- - WAL writes and fsyncs in IOContext IOCONTEXT_NORMAL
-- There is no test for blocks evicted from shared buffers, because we cannot
-- be sure of the state of shared buffers at the point the test is run.
@@ -621,6 +636,9 @@ SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_get_backend_io(pg_backend_pid())
WHERE object = 'relation' \gset my_io_sum_shared_before_
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal' \gset io_sum_wal_normal_before_
CREATE TABLE test_io_shared(a int);
INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
SELECT pg_stat_force_next_flush();
@@ -649,6 +667,13 @@ SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
SELECT :my_io_sum_shared_after_writes >= :my_io_sum_shared_before_writes;
SELECT current_setting('fsync') = 'off'
OR :my_io_sum_shared_after_fsyncs >= :my_io_sum_shared_before_fsyncs;
+SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
+ FROM pg_stat_io
+ WHERE context = 'normal' AND object = 'wal' \gset io_sum_wal_normal_after_
+SELECT current_setting('synchronous_commit') = 'on';
+SELECT :io_sum_wal_normal_after_writes > :io_sum_wal_normal_before_writes;
+SELECT current_setting('fsync') = 'off'
+ OR :io_sum_wal_normal_after_fsyncs > :io_sum_wal_normal_before_fsyncs;
-- Change the tablespace so that the table is rewritten directly, then SELECT
-- from it to cause it to be read back into shared buffers.
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 4e917f159aa..edc2470bcf9 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -2581,9 +2581,10 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para>
<para>
- Currently, I/O on relations (e.g. tables, indexes) is tracked. However,
- relation I/O which bypasses shared buffers (e.g. when moving a table from one
- tablespace to another) is currently not tracked.
+ Currently, I/O on relations (e.g. tables, indexes) and WAL activity are
+ tracked. However, relation I/O which bypasses shared buffers
+ (e.g. when moving a table from one tablespace to another) is currently
+ not tracked.
</para>
<table id="pg-stat-io-view" xreflabel="pg_stat_io">
@@ -2636,6 +2637,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
<literal>temp relation</literal>: Temporary relations.
</para>
</listitem>
+ <listitem>
+ <para>
+ <literal>wal</literal>: Write Ahead Logs.
+ </para>
+ </listitem>
</itemizedlist>
</para>
</entry>
@@ -2660,6 +2666,13 @@ description | Waiting for a newly initialized WAL file to reach durable storage
<literal>normal</literal>.
</para>
</listitem>
+ <listitem>
+ <para>
+ <literal>init</literal>: I/O operations performed while creating the
+ WAL segments are tracked in <varname>context</varname>
+ <literal>init</literal>.
+ </para>
+ </listitem>
<listitem>
<para>
<literal>vacuum</literal>: I/O operations performed outside of shared
--
2.47.2
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