From 4bab968b504fae9b1ebe7445d182a74619de4306 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Sat, 15 Mar 2025 12:29:57 -0400 Subject: [PATCH v2.9 15/30] bufmgr: Improve stats when buffer was read in concurrently Author: Reviewed-by: Discussion: https://postgr.es/m/ Backpatch: --- src/backend/storage/buffer/bufmgr.c | 41 ++++++++++++++++++----------- 1 file changed, 26 insertions(+), 15 deletions(-) diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 54add34f1a2..d783b33f78e 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -1490,19 +1490,6 @@ WaitReadBuffers(ReadBuffersOperation *operation) io_object = IOOBJECT_RELATION; } - /* - * We count all these blocks as read by this backend. This is traditional - * behavior, but might turn out to be not true if we find that someone - * else has beaten us and completed the read of some of these blocks. In - * that case the system globally double-counts, but we traditionally don't - * count this as a "hit", and we don't have a separate counter for "miss, - * but another backend completed the read". - */ - if (persistence == RELPERSISTENCE_TEMP) - pgBufferUsage.local_blks_read += nblocks; - else - pgBufferUsage.shared_blks_read += nblocks; - for (int i = 0; i < nblocks; ++i) { int io_buffers_len; @@ -1520,8 +1507,13 @@ WaitReadBuffers(ReadBuffersOperation *operation) if (!WaitReadBuffersCanStartIO(buffers[i], false)) { /* - * Report this as a 'hit' for this backend, even though it must - * have started out as a miss in PinBufferForBlock(). + * Report and track this as a 'hit' for this backend, even though + * it must have started out as a miss in PinBufferForBlock(). + * + * Some of the accesses would otherwise never be counted (e.g. + * pgBufferUsage) or counted as a miss (e.g. + * pgstat_count_buffer_hit(), as we always call + * pgstat_count_buffer_read()). */ TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + i, operation->smgr->smgr_rlocator.locator.spcOid, @@ -1529,6 +1521,20 @@ WaitReadBuffers(ReadBuffersOperation *operation) operation->smgr->smgr_rlocator.locator.relNumber, operation->smgr->smgr_rlocator.backend, true); + + if (persistence == RELPERSISTENCE_TEMP) + pgBufferUsage.local_blks_hit += 1; + else + pgBufferUsage.shared_blks_hit += 1; + + if (operation->rel) + pgstat_count_buffer_hit(operation->rel); + + pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0); + + if (VacuumCostActive) + VacuumCostBalance += VacuumCostPageHit; + continue; } @@ -1614,6 +1620,11 @@ WaitReadBuffers(ReadBuffersOperation *operation) false); } + if (persistence == RELPERSISTENCE_TEMP) + pgBufferUsage.local_blks_read += io_buffers_len; + else + pgBufferUsage.shared_blks_read += io_buffers_len; + if (VacuumCostActive) VacuumCostBalance += VacuumCostPageMiss * io_buffers_len; } -- 2.48.1.76.g4e746b1a31.dirty