diff options
| author | Andres Freund | 2023-03-30 21:23:14 +0000 |
|---|---|---|
| committer | Andres Freund | 2023-03-30 21:23:14 +0000 |
| commit | ca7b3c4c00042038ba9c282c4807e05c0a527e42 (patch) | |
| tree | 73ede8f1a9988dc4f699d2b2c95c75a7982af531 /src/backend/utils | |
| parent | 122376f028a0e31b91d6c6bad2a9a6e994708547 (diff) | |
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/utils')
| -rw-r--r-- | src/backend/utils/activity/pgstat_wal.c | 31 |
1 files changed, 16 insertions, 15 deletions
diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c index e8598b2f4e..94f1a3b06e 100644 --- a/src/backend/utils/activity/pgstat_wal.c +++ b/src/backend/utils/activity/pgstat_wal.c @@ -21,7 +21,7 @@ #include "executor/instrument.h" -PgStat_WalStats PendingWalStats = {0}; +PgStat_PendingWalStats PendingWalStats = {0}; /* * WAL usage counters saved from pgWALUsage at the previous call to @@ -70,7 +70,7 @@ bool pgstat_flush_wal(bool nowait) { PgStatShared_Wal *stats_shmem = &pgStatLocal.shmem->wal; - WalUsage diff = {0}; + WalUsage wal_usage_diff = {0}; Assert(IsUnderPostmaster || !IsPostmasterEnvironment); Assert(pgStatLocal.shmem != NULL && @@ -88,25 +88,26 @@ pgstat_flush_wal(bool nowait) * Calculate how much WAL usage counters were increased by subtracting the * previous counters from the current ones. */ - WalUsageAccumDiff(&diff, &pgWalUsage, &prevWalUsage); - PendingWalStats.wal_records = diff.wal_records; - PendingWalStats.wal_fpi = diff.wal_fpi; - PendingWalStats.wal_bytes = diff.wal_bytes; + WalUsageAccumDiff(&wal_usage_diff, &pgWalUsage, &prevWalUsage); if (!nowait) LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE); else if (!LWLockConditionalAcquire(&stats_shmem->lock, LW_EXCLUSIVE)) return true; -#define WALSTAT_ACC(fld) stats_shmem->stats.fld += PendingWalStats.fld - WALSTAT_ACC(wal_records); - WALSTAT_ACC(wal_fpi); - WALSTAT_ACC(wal_bytes); - WALSTAT_ACC(wal_buffers_full); - WALSTAT_ACC(wal_write); - WALSTAT_ACC(wal_sync); - WALSTAT_ACC(wal_write_time); - WALSTAT_ACC(wal_sync_time); +#define WALSTAT_ACC(fld, var_to_add) \ + (stats_shmem->stats.fld += var_to_add.fld) +#define WALSTAT_ACC_INSTR_TIME(fld) \ + (stats_shmem->stats.fld += INSTR_TIME_GET_MICROSEC(PendingWalStats.fld)) + WALSTAT_ACC(wal_records, wal_usage_diff); + WALSTAT_ACC(wal_fpi, wal_usage_diff); + WALSTAT_ACC(wal_bytes, wal_usage_diff); + WALSTAT_ACC(wal_buffers_full, PendingWalStats); + WALSTAT_ACC(wal_write, PendingWalStats); + WALSTAT_ACC(wal_sync, PendingWalStats); + WALSTAT_ACC_INSTR_TIME(wal_write_time); + WALSTAT_ACC_INSTR_TIME(wal_sync_time); +#undef WALSTAT_ACC_INSTR_TIME #undef WALSTAT_ACC LWLockRelease(&stats_shmem->lock); |