From 8aaa04b32d790da595684de58ae4fc2db96becff Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Thu, 30 Mar 2023 19:22:40 -0700 Subject: Track shared buffer hits in pg_stat_io Among other things, this should make it easier to calculate a useful cache hit ratio by excluding buffer reads via buffer access strategies. As buffer access strategies reuse buffers (and thus evict the prior buffer contents), it is normal to see reads on repeated scans of the same data. Author: Melanie Plageman Reviewed-by: Bertrand Drouvot Reviewed-by: Andres Freund Discussion: https://postgr.es/m/CAAKRu_beMa9Hzih40%3DXPYqhDVz6tsgUGTrhZXRo%3Dunp%2Bszb%3DUA%40mail.gmail.com --- src/backend/storage/buffer/localbuf.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) (limited to 'src/backend/storage/buffer/localbuf.c') diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c index 68b4817c67b..6f9e7eda57c 100644 --- a/src/backend/storage/buffer/localbuf.c +++ b/src/backend/storage/buffer/localbuf.c @@ -108,7 +108,7 @@ PrefetchLocalBuffer(SMgrRelation smgr, ForkNumber forkNum, */ BufferDesc * LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum, - bool *foundPtr, IOContext *io_context) + bool *foundPtr) { BufferTag newTag; /* identity of requested block */ LocalBufferLookupEnt *hresult; @@ -128,14 +128,6 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum, hresult = (LocalBufferLookupEnt *) hash_search(LocalBufHash, &newTag, HASH_FIND, NULL); - /* - * IO Operations on local buffers are only done in IOCONTEXT_NORMAL. Set - * io_context here (instead of after a buffer hit would have returned) for - * convenience since we don't have to worry about the overhead of calling - * IOContextForStrategy(). - */ - *io_context = IOCONTEXT_NORMAL; - if (hresult) { b = hresult->id; @@ -239,6 +231,7 @@ LocalBufferAlloc(SMgrRelation smgr, ForkNumber forkNum, BlockNumber blockNum, buf_state &= ~BM_DIRTY; pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state); + /* Temporary table I/O does not use Buffer Access Strategies */ pgstat_count_io_op(IOOBJECT_TEMP_RELATION, IOCONTEXT_NORMAL, IOOP_WRITE); pgBufferUsage.local_blks_written++; } -- cgit v1.2.3