From 8aeca70a90956387432a95fdd3b6365a785f0bbb Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Wed, 23 Jul 2025 01:27:44 +0300 Subject: [PATCH v1-backpatch] Limit checkpointer requests queue size If the number of sync requests is big enough, the palloc() call in AbsorbSyncRequests() will attempt to allocate more than 1 GB of memory, resulting in failure. This can lead to an infinite loop in the checkpointer process, as it repeatedly fails to absorb the pending requests. This commit limits the checkpointer requests queue size to 10M items. In addition to preventing the palloc() failure, this change helps to avoid long queue processing time. Also, this commit is for backpathing only. The master branch receives a more invasive yet comprehensive fix for this problem. Discussion: https://postgr.es/m/db4534f83a22a29ab5ee2566ad86ca92%40postgrespro.ru Backpatch-through: 13 --- src/backend/postmaster/checkpointer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c index fda91ffd1ce..903d83e7dea 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -135,6 +135,9 @@ static CheckpointerShmemStruct *CheckpointerShmem; /* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */ #define WRITES_PER_ABSORB 1000 +/* Max number of requests the checkpointer request queue can hold */ +#define MAX_CHECKPOINT_REQUESTS 10000000 + /* * GUC parameters */ @@ -970,7 +973,7 @@ CheckpointerShmemInit(void) */ MemSet(CheckpointerShmem, 0, size); SpinLockInit(&CheckpointerShmem->ckpt_lck); - CheckpointerShmem->max_requests = NBuffers; + CheckpointerShmem->max_requests = Min(NBuffers, MAX_CHECKPOINT_REQUESTS); ConditionVariableInit(&CheckpointerShmem->start_cv); ConditionVariableInit(&CheckpointerShmem->done_cv); } -- 2.39.5 (Apple Git-154)