From 6c349d83b607cfe20a685a5f66a4fa0e24dbe458 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 26 Feb 2025 09:49:59 +0900 Subject: Re-add GUC track_wal_io_timing This commit is a rework of 2421e9a51d20, about which Andres Freund has raised some concerns as it is valuable to have both track_io_timing and track_wal_io_timing in some cases, as the WAL write and fsync paths can be a major bottleneck for some workloads. Hence, it can be relevant to not calculate the WAL timings in environments where pg_test_timing performs poorly while capturing some IO data under track_io_timing for the non-WAL IO paths. The opposite can be also true: it should be possible to disable the non-WAL timings and enable the WAL timings (the previous GUC setups allowed this possibility). track_wal_io_timing is added back in this commit, controlling if WAL timings should be calculated in pg_stat_io for the read, fsync and write paths, as done previously with pg_stat_wal. pg_stat_wal previously tracked only the sync and write parts (now removed), read stats is new data tracked in pg_stat_io, all three are aggregated if track_wal_io_timing is enabled. The read part matters during recovery or if a XLogReader is used. Extra note: more control over if the types of timings calculated in pg_stat_io could be done with a GUC that lists pairs of (IOObject,IOOp). Reported-by: Andres Freund Author: Bertrand Drouvot Co-authored-by: Michael Paquier Discussion: https://postgr.es/m/3opf2wh2oljco6ldyqf7ukabw3jijnnhno6fjb4mlu6civ5h24@fcwmhsgmlmzu --- src/backend/access/transam/xlog.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'src/backend/access/transam/xlog.c') diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 919314f8258..799fc739e18 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -134,6 +134,7 @@ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ int wal_retrieve_retry_interval = 5000; int max_slot_wal_keep_size_mb = -1; int wal_decode_buffer_size = 512 * 1024; +bool track_wal_io_timing = false; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; @@ -2437,7 +2438,7 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible) /* * Measure I/O timing to write WAL data, for pg_stat_io. */ - start = pgstat_prepare_io_time(); + start = pgstat_prepare_io_time(track_wal_io_timing); pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); written = pg_pwrite(openLogFile, from, nleft, startoffset); @@ -3248,7 +3249,7 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli, errmsg("could not create file \"%s\": %m", tmppath))); /* Measure I/O timing when initializing segment */ - io_start = pgstat_prepare_io_time(); + io_start = pgstat_prepare_io_time(track_wal_io_timing); pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); save_errno = 0; @@ -3310,7 +3311,7 @@ XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli, } /* Measure I/O timing when flushing segment */ - io_start = pgstat_prepare_io_time(); + io_start = pgstat_prepare_io_time(track_wal_io_timing); pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC); if (pg_fsync(fd) != 0) @@ -8744,7 +8745,7 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli) /* * Measure I/O timing to sync the WAL file for pg_stat_io. */ - start = pgstat_prepare_io_time(); + start = pgstat_prepare_io_time(track_wal_io_timing); pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC); switch (wal_sync_method) -- cgit v1.2.3