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| author | Andres Freund <andres@anarazel.de> | 2023-03-30 14:23:14 -0700 |
|---|---|---|
| committer | Andres Freund <andres@anarazel.de> | 2023-03-30 14:23:14 -0700 |
| commit | ca7b3c4c00042038ba9c282c4807e05c0a527e42 (patch) | |
| tree | 73ede8f1a9988dc4f699d2b2c95c75a7982af531 /src/backend/access/transam/xlog.c | |
| parent | 122376f028a0e31b91d6c6bad2a9a6e994708547 (diff) | |
| download | postgresql-ca7b3c4c00042038ba9c282c4807e05c0a527e42.tar.gz postgresql-ca7b3c4c00042038ba9c282c4807e05c0a527e42.zip | |
pg_stat_wal: Accumulate time as instr_time instead of microseconds
In instr_time.h it is stated that:
* When summing multiple measurements, it's recommended to leave the
* running sum in instr_time form (ie, use INSTR_TIME_ADD or
* INSTR_TIME_ACCUM_DIFF) and convert to a result format only at the end.
The reason for that is that converting to microseconds is not cheap, and can
loose precision. Therefore this commit changes 'PendingWalStats' to use
'instr_time' instead of 'PgStat_Counter' while accumulating 'wal_write_time'
and 'wal_sync_time'.
Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/1feedb83-7aa9-cb4b-5086-598349d3f555@gmail.com
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 543d4d897ae..46821ad6056 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -2206,8 +2206,7 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible) instr_time duration; INSTR_TIME_SET_CURRENT(duration); - INSTR_TIME_SUBTRACT(duration, start); - PendingWalStats.wal_write_time += INSTR_TIME_GET_MICROSEC(duration); + INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_write_time, duration, start); } PendingWalStats.wal_write++; @@ -8204,8 +8203,7 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli) instr_time duration; INSTR_TIME_SET_CURRENT(duration); - INSTR_TIME_SUBTRACT(duration, start); - PendingWalStats.wal_sync_time += INSTR_TIME_GET_MICROSEC(duration); + INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, duration, start); } PendingWalStats.wal_sync++; |