This commit adds WAL IO stats to both pg_stat_io view and per-backend IO
statistics (pg_stat_get_backend_io()). This change is possible since
f92c854cf406, as WAL IO is not counted in blocks in some code paths
where its stats data is measured (like WAL read in xlogreader.c).
IOContext gains IOCONTEXT_INIT and IOObject IOOBJECT_WAL, with the
following combinations allowed:
- IOOBJECT_WAL/IOCONTEXT_NORMAL is used to track I/O operations done on
already-created WAL segments.
- IOOBJECT_WAL/IOCONTEXT_INIT is used for tracking I/O operations done
when initializing WAL segments.
The core changes are done in pg_stat_io.c, backend statistics inherit
them. Backend statistics and pg_stat_io are now available for the WAL
writer, the WAL receiver and the WAL summarizer processes.
I/O timing data is controlled by the GUC track_io_timing, like the
existing data of pg_stat_io for consistency. The timings related to
IOOBJECT_WAL show up if the GUC is enabled (disabled by default).
Bump pgstats file version, due to the additions in IOObject and
IOContext, impacting the amount of data written for the fixed-numbered
IO stats kind in the pgstats file.
Author: Nazir Bilal Yavuz
Reviewed-by: Bertrand Drouvot, Nitin Jadhav, Amit Kapila, Michael
Paquier, Melanie Plageman, Bharath Rupireddy
Discussion: https://postgr.es/m/CAN55FZ3AiQ+ZMxUuXnBpd0Rrh1YhwJ5FudkHg=JU0P+-W8T4Vg@mail.gmail.com
</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">
<literal>temp relation</literal>: Temporary relations.
</para>
</listitem>
+ <listitem>
+ <para>
+ <literal>wal</literal>: Write Ahead Logs.
+ </para>
+ </listitem>
</itemizedlist>
</para>
</entry>
<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
{
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_io and/or
+ * pg_stat_wal.
+ */
+ start = pgstat_prepare_io_time(track_io_timing || track_wal_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.
int fd;
int save_errno;
int open_flags = O_RDWR | O_CREAT | O_EXCL | PG_BINARY;
+ instr_time io_start;
Assert(logtli != 0);
(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)
}
pgstat_report_wait_end();
+ /*
+ * A full segment worth of data is written when using wal_init_zero. One
+ * byte is written when not using it.
+ */
+ pgstat_count_io_op_time(IOOBJECT_WAL, IOCONTEXT_INIT, IOOP_WRITE,
+ io_start, 1,
+ wal_init_zero ? wal_segment_size : 1);
+
if (save_errno)
{
/*
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)
{
}
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(),
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_io and/or
+ * pg_stat_wal.
+ */
+ start = pgstat_prepare_io_time(track_io_timing || track_wal_io_timing);
pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);
switch (wal_sync_method)
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++;
}
#ifndef FRONTEND
#include "pgstat.h"
+#include "storage/bufmgr.h"
#else
#include "common/logging.h"
#endif
char *p;
XLogRecPtr recptr;
Size nbytes;
+#ifndef FRONTEND
+ instr_time io_start;
+#endif
p = buf;
recptr = startptr;
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
#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)
#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"
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);
/* 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)
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)
{
}
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);
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:
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;
}
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],
return "bulkread";
case IOCONTEXT_BULKWRITE:
return "bulkwrite";
+ case IOCONTEXT_INIT:
+ return "init";
case IOCONTEXT_NORMAL:
return "normal";
case IOCONTEXT_VACUUM:
return "relation";
case IOOBJECT_TEMP_RELATION:
return "temp relation";
+ case IOOBJECT_WAL:
+ return "wal";
}
elog(ERROR, "unrecognized IOObject value: %d", io_object);
* - 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.
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:
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;
}
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.
/*
* 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.
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
* ------------------------------------------------------------
*/
-#define PGSTAT_FILE_FORMAT_ID 0x01A5BCB2
+#define PGSTAT_FILE_FORMAT_ID 0x01A5BCB3
typedef struct PgStat_ArchiverStats
{
{
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;
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
-----
-- - 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
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();
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
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
-----
-- - 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.
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();
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.
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