Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit5d4298e

Browse files
committed
pg_stat_statements: Avoid some locking during PGSS entry scans
A single PGSS entry's spinlock is used to be able to modify "counters"without holding pgss->lock exclusively, as mentioned at the top ofpg_stat_statements.c and within pgssEntry.Within a single pgssEntry, stats_since and minmax_stats_since are nevermodified without holding pgss->lock exclusively, so there is no need tohold an entry's spinlock when reading stats_since andminmax_stats_since, as done when scanning all the PGSS entries forfunction calls of pg_stat_statements().This also restores the consistency between the code and the commentsabout the entry's spinlock usage. This change is a performanceimprovement (it can be argued that this is a logic bug), so there is noneed for a backpatch. This saves two instructions from being read whileholding an entry's spinlock.Author: Karina LitskevichReviewed-by: Michael Paquier, wenhui qiuDiscussion:https://postgr.es/m/CACiT8ibhCmzbcOxM0v4pRLH3abk-95LPkt7_uC2JMP+miPjxsg@mail.gmail.com
1 parent29d66b2 commit5d4298e

File tree

1 file changed

+6
-1
lines changed

1 file changed

+6
-1
lines changed

‎contrib/pg_stat_statements/pg_stat_statements.c

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1869,9 +1869,14 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
18691869
/* copy counters to a local variable to keep locking time short */
18701870
SpinLockAcquire(&entry->mutex);
18711871
tmp=entry->counters;
1872+
SpinLockRelease(&entry->mutex);
1873+
1874+
/*
1875+
* The spinlock is not required when reading these two as they are
1876+
* always updated when holding pgss->lock exclusively.
1877+
*/
18721878
stats_since=entry->stats_since;
18731879
minmax_stats_since=entry->minmax_stats_since;
1874-
SpinLockRelease(&entry->mutex);
18751880

18761881
/* Skip entry if unexecuted (ie, it's a pending "sticky" entry) */
18771882
if (IS_STICKY(tmp))

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp