From 7e552c4364f47129b05a17d374dfce0608d4559f Mon Sep 17 00:00:00 2001 From: Ashutosh Bapat Date: Mon, 17 Aug 2026 22:12:29 +0530 Subject: [PATCH v20260817] BgBufferSync refactor reusable_buffers increment reusable_buffers gets incremented when sync_state has BUF_WRITTEN set or when it as BUF_REUSABLE set. The way code is written it feels like that resuable_buffers is incremented even when the buffer is not reusable but written. The feeling is not true. If BUF_WRITTEN is set by SyncOneBuffer(), BUF_REUSABLE should have been set since the function is called with skip_recently_used = true, which instructs it to only write buffers which are reusable. Rearrange the code so as to avoid the confusion. Author: Ashutosh Bapat Reviewed-by: Xuneng Zhou Discussion: https://www.postgresql.org/message-id/CAMCWMe1dgsT0qzVL9TufPy%3DXBF1j1gd76VLysR7fF5J4hP1E-g%40mail.gmail.com --- src/backend/storage/buffer/bufmgr.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 17f142e4c5b..52d90c82301 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -4083,17 +4083,23 @@ BgBufferSync(WritebackContext *wb_context) } num_to_scan--; + if (sync_state & BUF_REUSABLE) + reusable_buffers++; + if (sync_state & BUF_WRITTEN) { - reusable_buffers++; + /* + * We instructed SyncOneBuffer not to write a recently used + * buffer. + */ + Assert(sync_state & BUF_REUSABLE); + if (++num_written >= bgwriter_lru_maxpages) { PendingBgWriterStats.maxwritten_clean++; break; } } - else if (sync_state & BUF_REUSABLE) - reusable_buffers++; } PendingBgWriterStats.buf_written_clean += num_written; base-commit: 51c43a5dbd86ad8461544e54c00bd9f487abfacd -- 2.34.1