From 7d9911908130fd99b502c6c2d7573fb28a542c59 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Tue, 18 Mar 2025 14:40:06 -0400 Subject: [PATCH v2.14 19/29] aio: Experimental heuristics to increase batching in read_stream.c Author: Reviewed-by: Discussion: https://postgr.es/m/ Backpatch: --- src/backend/storage/aio/read_stream.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/src/backend/storage/aio/read_stream.c b/src/backend/storage/aio/read_stream.c index 36c54fb695b..cec93129f58 100644 --- a/src/backend/storage/aio/read_stream.c +++ b/src/backend/storage/aio/read_stream.c @@ -404,6 +404,30 @@ read_stream_start_pending_read(ReadStream *stream) static void read_stream_look_ahead(ReadStream *stream) { + /* + * Batch-submitting multiple IOs is more efficient than doing so + * one-by-one. If we just ramp up to the max, we'll only be allowed to + * submit one io_combine_limit sized IO. Defer submitting IO in that case. + * + * FIXME: This needs better heuristics. + */ +#if 1 + if (!stream->sync_mode && stream->distance > (io_combine_limit * 8)) + { + if (stream->pinned_buffers + stream->pending_read_nblocks > ((stream->distance * 3) / 4)) + { +#if 0 + ereport(LOG, + errmsg("reduce reduce reduce: pinned: %d, pending: %d, distance: %d", + stream->pinned_buffers, + stream->pending_read_nblocks, + stream->distance)); +#endif + return; + } + } +#endif + /* * Allow amortizing the cost of submitting IO over multiple IOs. This * requires that we don't do any operations that could lead to a deadlock -- 2.48.1.76.g4e746b1a31.dirty