From 13559de95383b493a6e6384dcb621947bb8bcc23 Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Sun, 27 Jul 2025 15:10:01 +0300 Subject: [PATCH] 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 199f008bcda..c5e86d3317e 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -130,6 +130,9 @@ 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 */ @@ -914,7 +917,7 @@ 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); } -- 2.47.2