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help / color / mirror / Atom feedFrom: Andres Freund <andres@anarazel.de>
Subject: [PATCH v2.12 18/28] aio: Experimental heuristics to increase batching in read_stream.c
Date: Tue, 18 Mar 2025 14:40:06 -0400
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 f675168e89a..039d7dc71a5 100644
--- a/src/backend/storage/aio/read_stream.c
+++ b/src/backend/storage/aio/read_stream.c
@@ -403,6 +403,30 @@ 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
--5i73spx2p4vwf7fe
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v2.12-0019-aio-Implement-smgr-md-fd-write-support.patch"
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To: pgsql-hackers@postgresql.org
Cc: andres@anarazel.de
Subject: Re: [PATCH v2.12 18/28] aio: Experimental heuristics to increase batching in read_stream.c
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