From b0bb4b478b27c2a38bf819ee927be9167e551d28 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Sat, 31 Aug 2024 21:39:30 -0400 Subject: [PATCH v2.3 22/30] aio: Very-WIP: read_stream.c adjustments for real AIO Things that need to be fixed / are fixed in this: - max pinned buffers should be limited by io_combine_limit, not * 4 - overflow distance - pins need to be limited in more places --- src/include/storage/bufmgr.h | 2 ++ src/backend/storage/aio/read_stream.c | 31 +++++++++++++++++++++------ src/backend/storage/buffer/bufmgr.c | 3 ++- 3 files changed, 28 insertions(+), 8 deletions(-) diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 46ee957e99c..f205643c4ef 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -119,6 +119,8 @@ typedef struct BufferManagerRelation #define READ_BUFFERS_ISSUE_ADVICE (1 << 1) /* IO will immediately be waited for */ #define READ_BUFFERS_SYNCHRONOUSLY (1 << 2) +/* caller will issue more io, don't submit */ +#define READ_BUFFERS_MORE_MORE_MORE (1 << 3) struct ReadBuffersOperation diff --git a/src/backend/storage/aio/read_stream.c b/src/backend/storage/aio/read_stream.c index e4414b2e915..c2211cab02a 100644 --- a/src/backend/storage/aio/read_stream.c +++ b/src/backend/storage/aio/read_stream.c @@ -90,6 +90,7 @@ #include "postgres.h" #include "miscadmin.h" +#include "storage/aio.h" #include "storage/fd.h" #include "storage/smgr.h" #include "storage/read_stream.h" @@ -240,14 +241,18 @@ read_stream_start_pending_read(ReadStream *stream, bool suppress_advice) /* * If advice hasn't been suppressed, this system supports it, and this * isn't a strictly sequential pattern, then we'll issue advice. + * + * XXX: Used to also check stream->pending_read_blocknum != + * stream->seq_blocknum */ if (!suppress_advice && - stream->advice_enabled && - stream->pending_read_blocknum != stream->seq_blocknum) + stream->advice_enabled) flags = READ_BUFFERS_ISSUE_ADVICE; else flags = 0; + flags |= READ_BUFFERS_MORE_MORE_MORE; + /* We say how many blocks we want to read, but may be smaller on return. */ buffer_index = stream->next_buffer_index; io_index = stream->next_io_index; @@ -306,6 +311,14 @@ read_stream_start_pending_read(ReadStream *stream, bool suppress_advice) static void read_stream_look_ahead(ReadStream *stream, bool suppress_advice) { + if (stream->distance > (io_combine_limit * 8)) + { + if (stream->pinned_buffers + stream->pending_read_nblocks > ((stream->distance * 3) / 4)) + { + return; + } + } + while (stream->ios_in_progress < stream->max_ios && stream->pinned_buffers + stream->pending_read_nblocks < stream->distance) { @@ -355,6 +368,7 @@ read_stream_look_ahead(ReadStream *stream, bool suppress_advice) { /* And we've hit the limit. Rewind, and stop here. */ read_stream_unget_block(stream, blocknum); + pgaio_submit_staged(); return; } } @@ -379,6 +393,8 @@ read_stream_look_ahead(ReadStream *stream, bool suppress_advice) stream->distance == 0) && stream->ios_in_progress < stream->max_ios) read_stream_start_pending_read(stream, suppress_advice); + + pgaio_submit_staged(); } /* @@ -442,7 +458,7 @@ read_stream_begin_impl(int flags, * overflow (even though that's not possible with the current GUC range * limits), allowing also for the spare entry and the overflow space. */ - max_pinned_buffers = Max(max_ios * 4, io_combine_limit); + max_pinned_buffers = Max(max_ios * io_combine_limit, io_combine_limit); max_pinned_buffers = Min(max_pinned_buffers, PG_INT16_MAX - io_combine_limit - 1); @@ -493,10 +509,11 @@ read_stream_begin_impl(int flags, * direct I/O isn't enabled, the caller hasn't promised sequential access * (overriding our detection heuristics), and max_ios hasn't been set to * zero. + * + * FIXME: Used to also check (io_direct_flags & IO_DIRECT_DATA) == 0 && + * (flags & READ_STREAM_SEQUENTIAL) == 0 */ - if ((io_direct_flags & IO_DIRECT_DATA) == 0 && - (flags & READ_STREAM_SEQUENTIAL) == 0 && - max_ios > 0) + if (max_ios > 0) stream->advice_enabled = true; #endif @@ -727,7 +744,7 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data) if (++stream->oldest_io_index == stream->max_ios) stream->oldest_io_index = 0; - if (stream->ios[io_index].op.flags & READ_BUFFERS_ISSUE_ADVICE) + if (stream->ios[io_index].op.flags & (READ_BUFFERS_ISSUE_ADVICE | READ_BUFFERS_MORE_MORE_MORE)) { /* Distance ramps up fast (behavior C). */ distance = stream->distance * 2; diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 70f1da84083..118a6e1ca31 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -1752,7 +1752,8 @@ AsyncReadBuffers(ReadBuffersOperation *operation, if (did_start_io_overall) { - pgaio_submit_staged(); + if (!(flags & READ_BUFFERS_MORE_MORE_MORE)) + pgaio_submit_staged(); return true; } else -- 2.48.1.76.g4e746b1a31.dirty