Increase size of shared memory for pg_commit_ts

alvherre · alvherre · commit 4c83e59e01a8 · 2021-11-30T14:29:31.000-03:00
Like 5364b35 did for pg_commit, change the formula used to determine number of pg_commit_ts buffers, which helps performance with larger servers. Discussion: https://postgr.es/m/20210115220744.GA24457@alvherre.pgsql Reviewed-by: Noah Misch <noah@leadboat.com> Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
@@ -508,13 +508,14 @@ pg_xact_commit_timestamp_origin(PG_FUNCTION_ARGS)
 /*
  * Number of shared CommitTS buffers.
  *
- * We use a very similar logic as for the number of CLOG buffers; see comments
- * in CLOGShmemBuffers.
+ * We use a very similar logic as for the number of CLOG buffers (except we
+ * scale up twice as fast with shared buffers, and the maximum is twice as
+ * high); see comments in CLOGShmemBuffers.
  */
 Size
 CommitTsShmemBuffers(void)
 {
-	return Min(16, Max(4, NBuffers / 1024));
+	return Min(256, Max(4, NBuffers / 256));
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -508,13 +508,14 @@ pg_xact_commit_timestamp_origin(PG_FUNCTION_ARGS)`
`508`	`508`	`/*`
`509`	`509`	`* Number of shared CommitTS buffers.`
`510`	`510`	`*`
`511`		`- * We use a very similar logic as for the number of CLOG buffers; see comments`
`512`		`- * in CLOGShmemBuffers.`
	`511`	`+ * We use a very similar logic as for the number of CLOG buffers (except we`
	`512`	`+ * scale up twice as fast with shared buffers, and the maximum is twice as`
	`513`	`+ * high); see comments in CLOGShmemBuffers.`
`513`	`514`	`*/`
`514`	`515`	`Size`
`515`	`516`	`CommitTsShmemBuffers(void)`
`516`	`517`	`{`
`517`		`- return Min(16, Max(4, NBuffers / 1024));`
	`518`	`+ return Min(256, Max(4, NBuffers / 256));`
`518`	`519`	`}`
`519`	`520`
`520`	`521`	`/*`