From 25c18f6918c064e36865e8969fda8300a2864eca Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 12 Jun 2024 23:38:41 +0300 Subject: [PATCH 1/1] Clamp result of MultiXactMemberFreezeThreshold The purpose of the function is to reduce the effective autovacuum_multixact_freeze_max_age, to make multixid freezing more aggressive, if the multixact members SLRU is approaching wraparound. The returned value should thereore never be greater than plain autovacuum_multixact_freeze_max_age is. Discussion: xxx --- src/backend/access/transam/multixact.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 54c916e034..a4e732a3f5 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -2932,6 +2932,7 @@ MultiXactMemberFreezeThreshold(void) uint32 multixacts; uint32 victim_multixacts; double fraction; + int result; /* If we can't determine member space utilization, assume the worst. */ if (!ReadMultiXactCounts(&multixacts, &members)) @@ -2953,7 +2954,13 @@ MultiXactMemberFreezeThreshold(void) /* fraction could be > 1.0, but lowest possible freeze age is zero */ if (victim_multixacts > multixacts) return 0; - return multixacts - victim_multixacts; + result = multixacts - victim_multixacts; + + /* + * Clamp to autovacuum_multixact_freeze_max_age, so that we never make + * autovacuum less aggressive than it would otherwise be. + */ + return Min(result, autovacuum_multixact_freeze_max_age); } typedef struct mxtruncinfo -- 2.39.2