diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 967de73596..56eb55bab7 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -7450,7 +7450,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; Enables timing of database I/O calls. This parameter is off by - default, because it will repeatedly query the operating system for + default, as it will repeatedly query the operating system for the current time, which may cause significant overhead on some platforms. You can use the tool to measure the overhead of timing on your system. @@ -7464,6 +7464,27 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; + + track_wal_io_timing (boolean) + + track_wal_io_timing configuration parameter + + + + + Enables timing of WAL I/O calls. This parameter is off by default, + as it will repeatedly query the operating system for + the current time, which may cause significant overhead on some + platforms. You can use the tool to + measure the overhead of timing on your system. + I/O timing information is + displayed in + pg_stat_wal. Only superusers can + change this setting. + + + + track_functions (enum) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index 3513e127b7..1520cef505 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3487,6 +3487,62 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i + + + wal_write bigint + + + Number of times WAL buffers were written out to disk via + XLogWrite, which is invoked during an + XLogFlush request (see ) + + + + + + wal_sync bigint + + + Number of times WAL files were synced to disk via + issue_xlog_fsync, which is invoked during an + XLogFlush request (see ) + while was set to one of the + "sync at commit" options (i.e., fdatasync, + fsync, or fsync_writethrough). + + + + + + wal_write_time double precision + + + Total amount of time spent writing WAL buffers were written out to disk via + XLogWrite, which is invoked during an + XLogFlush request (see ), + excluding sync time unless + is either open_datasync or + open_sync. Units are in milliseconds with microsecond resolution. + This is zero when is disabled. + + + + + + wal_sync_time double precision + + + Total amount of time spent syncing WAL files to disk via + issue_xlog_fsync, which is invoked during an + XLogFlush request (see ) + while was set to one of the + "sync at commit" options (i.e., fdatasync, + fsync, or fsync_writethrough). + Units are in milliseconds with microsecond resolution. + This is zero when is disabled. + + + stats_reset timestamp with time zone diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml index f75527f764..06e4b37012 100644 --- a/doc/src/sgml/wal.sgml +++ b/doc/src/sgml/wal.sgml @@ -663,7 +663,9 @@ the WAL buffers in shared memory. If there is no space for the new record, XLogInsertRecord will have to write (move to kernel cache) a few filled WAL - buffers. This is undesirable because XLogInsertRecord + buffers (the tally of this event is reported in + wal_buffers_full in ). + This is undesirable because XLogInsertRecord is used on every database low level modification (for example, row insertion) at a time when an exclusive lock is held on affected data pages, so the operation needs to be as fast as possible. What @@ -672,8 +674,12 @@ time. Normally, WAL buffers should be written and flushed by an XLogFlush request, which is made, for the most part, at transaction commit time to ensure that - transaction records are flushed to permanent storage. On systems - with high log output, XLogFlush requests might + transaction records are flushed to permanent storage. + XLogFlush calls XLogWrite to write + and issue_xlog_fsync to flush them, which are counted as + wal_write and wal_sync in + . On systems with high log output, + XLogFlush requests might not occur often enough to prevent XLogInsertRecord from having to do writes. On such systems one should increase the number of WAL buffers by diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index fe56324439..24c3dd32f8 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -110,6 +110,7 @@ int CommitDelay = 0; /* precommit delay in microseconds */ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ int wal_retrieve_retry_interval = 5000; int max_slot_wal_keep_size_mb = -1; +bool track_wal_io_timing = false; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; @@ -2533,6 +2534,7 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible) Size nbytes; Size nleft; int written; + instr_time start; /* OK to write the page(s) */ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ; @@ -2541,9 +2543,30 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible) do { errno = 0; + + /* Measure I/O timing to write WAL data */ + if (track_wal_io_timing) + INSTR_TIME_SET_CURRENT(start); + pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); written = pg_pwrite(openLogFile, from, nleft, startoffset); pgstat_report_wait_end(); + + /* + * Increment the I/O timing and the number of times WAL data + * were written out to disk. + */ + if (track_wal_io_timing) + { + instr_time duration; + + INSTR_TIME_SET_CURRENT(duration); + INSTR_TIME_SUBTRACT(duration, start); + WalStats.m_wal_write_time += INSTR_TIME_GET_MICROSEC(duration); + } + + WalStats.m_wal_write++; + if (written <= 0) { char xlogfname[MAXFNAMELEN]; @@ -10526,6 +10549,20 @@ void issue_xlog_fsync(int fd, XLogSegNo segno) { char *msg = NULL; + instr_time start; + + /* + * Quick exit if fsync is disabled or write() has already synced the WAL + * file. + */ + if (!enableFsync || + sync_method == SYNC_METHOD_OPEN || + sync_method == SYNC_METHOD_OPEN_DSYNC) + return; + + /* Measure I/O timing to sync the WAL file */ + if (track_wal_io_timing) + INSTR_TIME_SET_CURRENT(start); pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC); switch (sync_method) @@ -10548,7 +10585,8 @@ issue_xlog_fsync(int fd, XLogSegNo segno) #endif case SYNC_METHOD_OPEN: case SYNC_METHOD_OPEN_DSYNC: - /* write synced it already */ + /* not reachable */ + Assert(false); break; default: elog(PANIC, "unrecognized wal_sync_method: %d", sync_method); @@ -10570,6 +10608,20 @@ issue_xlog_fsync(int fd, XLogSegNo segno) } pgstat_report_wait_end(); + + /* + * Increment the I/O timing and the number of times WAL files were synced. + */ + if (track_wal_io_timing) + { + instr_time duration; + + INSTR_TIME_SET_CURRENT(duration); + INSTR_TIME_SUBTRACT(duration, start); + WalStats.m_wal_sync_time += INSTR_TIME_GET_MICROSEC(duration); + } + + WalStats.m_wal_sync++; } /* diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql index fc94a73a54..51ba1b5826 100644 --- a/src/backend/catalog/system_views.sql +++ b/src/backend/catalog/system_views.sql @@ -1005,6 +1005,10 @@ CREATE VIEW pg_stat_wal AS w.wal_fpi, w.wal_bytes, w.wal_buffers_full, + w.wal_write, + w.wal_sync, + w.wal_write_time, + w.wal_sync_time, w.stats_reset FROM pg_stat_get_wal() w; diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c index 0bbeece19d..3894f4a270 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -505,7 +505,7 @@ CheckpointerMain(void) pgstat_send_bgwriter(); /* Send WAL statistics to the stats collector. */ - pgstat_send_wal(); + pgstat_report_wal(); /* * If any checkpoint flags have been set, redo the loop to handle the diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index f75b52719d..cf1d3ea366 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -146,8 +146,8 @@ PgStat_MsgWal WalStats; /* * WAL usage counters saved from pgWALUsage at the previous call to - * pgstat_send_wal(). This is used to calculate how much WAL usage - * happens between pgstat_send_wal() calls, by substracting + * pgstat_report_wal(). This is used to calculate how much WAL usage + * happens between pgstat_report_wal() calls, by substracting * the previous counters from the current ones. */ static WalUsage prevWalUsage; @@ -975,7 +975,7 @@ pgstat_report_stat(bool disconnect) pgstat_send_funcstats(); /* Send WAL statistics */ - pgstat_send_wal(); + pgstat_report_wal(); /* Finally send SLRU statistics */ pgstat_send_slru(); @@ -3118,7 +3118,7 @@ pgstat_initialize(void) } /* - * Initialize prevWalUsage with pgWalUsage so that pgstat_send_wal() can + * Initialize prevWalUsage with pgWalUsage so that pgstat_report_wal() can * calculate how much pgWalUsage counters are increased by substracting * prevWalUsage from pgWalUsage. */ @@ -4667,17 +4667,17 @@ pgstat_send_bgwriter(void) } /* ---------- - * pgstat_send_wal() - + * pgstat_report_wal() - * - * Send WAL statistics to the collector + * Calculate how much WAL usage counters are increased and send + * WAL statistics to the collector. + * + * Must be called by processes that generate WAL. * ---------- */ void -pgstat_send_wal(void) +pgstat_report_wal(void) { - /* We assume this initializes to zeroes */ - static const PgStat_MsgWal all_zeroes; - WalUsage walusage; /* @@ -4692,6 +4692,33 @@ pgstat_send_wal(void) WalStats.m_wal_fpi = walusage.wal_fpi; WalStats.m_wal_bytes = walusage.wal_bytes; + /* + * Send WAL stats message to the collector. + */ + pgstat_send_wal(true); + + /* + * Save the current counters for the subsequent calculation of WAL usage. + */ + prevWalUsage = pgWalUsage; +} + +/* ---------- + * pgstat_send_wal() - + * + * Send WAL statistics to the collector. + * + * If 'force' is not set, WAL stats message is only sent if enough time has + * passed since last one was sent to reach PGSTAT_STAT_INTERVAL. + * ---------- + */ +void +pgstat_send_wal(bool force) +{ + /* We assume this initializes to zeroes */ + static const PgStat_MsgWal all_zeroes; + static TimestampTz sendTime = 0; + /* * This function can be called even if nothing at all has happened. In * this case, avoid sending a completely empty message to the stats @@ -4700,17 +4727,25 @@ pgstat_send_wal(void) if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) return; + if (!force) + { + TimestampTz now = GetCurrentTimestamp(); + + /* + * Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL + * msec since we last sent one. + */ + if (!TimestampDifferenceExceeds(sendTime, now, PGSTAT_STAT_INTERVAL)) + return; + sendTime = now; + } + /* * Prepare and send the message */ pgstat_setheader(&WalStats.m_hdr, PGSTAT_MTYPE_WAL); pgstat_send(&WalStats, sizeof(WalStats)); - /* - * Save the current counters for the subsequent calculation of WAL usage. - */ - prevWalUsage = pgWalUsage; - /* * Clear out the statistics buffer, so it can be re-used. */ @@ -6892,6 +6927,10 @@ pgstat_recv_wal(PgStat_MsgWal *msg, int len) walStats.wal_fpi += msg->m_wal_fpi; walStats.wal_bytes += msg->m_wal_bytes; walStats.wal_buffers_full += msg->m_wal_buffers_full; + walStats.wal_write += msg->m_wal_write; + walStats.wal_write_time += msg->m_wal_write_time; + walStats.wal_sync += msg->m_wal_sync; + walStats.wal_sync_time += msg->m_wal_sync_time; } /* ---------- diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c index 4f1a8e356b..132df29aba 100644 --- a/src/backend/postmaster/walwriter.c +++ b/src/backend/postmaster/walwriter.c @@ -253,6 +253,9 @@ WalWriterMain(void) else if (left_till_hibernate > 0) left_till_hibernate--; + /* Send WAL statistics to the stats collector */ + pgstat_send_wal(false); + /* * Sleep until we are signaled or WalWriterDelay has elapsed. If we * haven't done anything useful for quite some time, lengthen the diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 62bff52638..c7540eec12 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1799,7 +1799,7 @@ pg_stat_get_buf_alloc(PG_FUNCTION_ARGS) Datum pg_stat_get_wal(PG_FUNCTION_ARGS) { -#define PG_STAT_GET_WAL_COLS 5 +#define PG_STAT_GET_WAL_COLS 9 TupleDesc tupdesc; Datum values[PG_STAT_GET_WAL_COLS]; bool nulls[PG_STAT_GET_WAL_COLS]; @@ -1820,7 +1820,15 @@ pg_stat_get_wal(PG_FUNCTION_ARGS) NUMERICOID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 4, "wal_buffers_full", INT8OID, -1, 0); - TupleDescInitEntry(tupdesc, (AttrNumber) 5, "stats_reset", + TupleDescInitEntry(tupdesc, (AttrNumber) 5, "wal_write", + INT8OID, -1, 0); + TupleDescInitEntry(tupdesc, (AttrNumber) 6, "wal_sync", + INT8OID, -1, 0); + TupleDescInitEntry(tupdesc, (AttrNumber) 7, "wal_write_time", + FLOAT8OID, -1, 0); + TupleDescInitEntry(tupdesc, (AttrNumber) 8, "wal_sync_time", + FLOAT8OID, -1, 0); + TupleDescInitEntry(tupdesc, (AttrNumber) 9, "stats_reset", TIMESTAMPTZOID, -1, 0); BlessTupleDesc(tupdesc); @@ -1840,7 +1848,13 @@ pg_stat_get_wal(PG_FUNCTION_ARGS) Int32GetDatum(-1)); values[3] = Int64GetDatum(wal_stats->wal_buffers_full); - values[4] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp); + values[4] = Int64GetDatum(wal_stats->wal_write); + values[5] = Int64GetDatum(wal_stats->wal_sync); + + /* convert counter from microsec to millisec for display */ + values[6] = Float8GetDatum((double) wal_stats->wal_write_time / 1000.0); + values[7] = Float8GetDatum((double) wal_stats->wal_sync_time / 1000.0); + values[8] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp); /* Returns the record as Datum */ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls))); diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 442850e8ad..da05b5acb1 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -1485,6 +1485,15 @@ static struct config_bool ConfigureNamesBool[] = false, NULL, NULL, NULL }, + { + {"track_wal_io_timing", PGC_SUSET, STATS_COLLECTOR, + gettext_noop("Collects timing statistics for WAL I/O activity."), + NULL + }, + &track_wal_io_timing, + false, + NULL, NULL, NULL + }, { {"update_process_title", PGC_SUSET, PROCESS_TITLE, diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index ee06528bb0..c6483fa1ff 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -586,6 +586,7 @@ #track_activities = on #track_counts = on #track_io_timing = off +#track_wal_io_timing = off #track_functions = none # none, pl, all #track_activity_query_size = 1024 # (change requires restart) #stats_temp_directory = 'pg_stat_tmp' diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h index 75ec1073bd..1e53d9d4ca 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -131,6 +131,7 @@ extern int recovery_min_apply_delay; extern char *PrimaryConnInfo; extern char *PrimarySlotName; extern bool wal_receiver_create_temp_slot; +extern bool track_wal_io_timing; /* indirectly set via GUC system */ extern TransactionId recoveryTargetXid; diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index 7ba7c2ff8a..933659efc6 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -5546,9 +5546,9 @@ { oid => '1136', descr => 'statistics: information about WAL activity', proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's', proparallel => 'r', prorettype => 'record', proargtypes => '', - proallargtypes => '{int8,int8,numeric,int8,timestamptz}', - proargmodes => '{o,o,o,o,o}', - proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,stats_reset}', + proallargtypes => '{int8,int8,numeric,int8,int8,int8,float8,float8,timestamptz}', + proargmodes => '{o,o,o,o,o,o,o,o,o}', + proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,wal_write,wal_sync,wal_write_time,wal_sync_time,stats_reset}', prosrc => 'pg_stat_get_wal' }, { oid => '2306', descr => 'statistics: information about SLRU caches', diff --git a/src/include/pgstat.h b/src/include/pgstat.h index 724068cf87..7dd375a114 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -474,6 +474,12 @@ typedef struct PgStat_MsgWal PgStat_Counter m_wal_fpi; uint64 m_wal_bytes; PgStat_Counter m_wal_buffers_full; + PgStat_Counter m_wal_write; + PgStat_Counter m_wal_sync; + PgStat_Counter m_wal_write_time; /* time spend writing wal records in + * micro seconds */ + PgStat_Counter m_wal_sync_time; /* time spend syncing wal records in micro + * seconds */ } PgStat_MsgWal; /* ---------- @@ -839,6 +845,10 @@ typedef struct PgStat_WalStats PgStat_Counter wal_fpi; uint64 wal_bytes; PgStat_Counter wal_buffers_full; + PgStat_Counter wal_write; + PgStat_Counter wal_sync; + PgStat_Counter wal_write_time; + PgStat_Counter wal_sync_time; TimestampTz stat_reset_timestamp; } PgStat_WalStats; @@ -1590,7 +1600,8 @@ extern void pgstat_twophase_postabort(TransactionId xid, uint16 info, extern void pgstat_send_archiver(const char *xlog, bool failed); extern void pgstat_send_bgwriter(void); -extern void pgstat_send_wal(void); +extern void pgstat_report_wal(void); +extern void pgstat_send_wal(bool force); /* ---------- * Support functions for the SQL-callable functions to