Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitf4d0730

Browse files
anarazelmacdice
andcommitted
aio: Basic read_stream adjustments for real AIO
Adapt the read stream logic for real AIO:- If AIO is enabled, we shouldn't issue advice, but if it isn't, we should continue issuing advice- AIO benefits from reading ahead with direct IO- If effective_io_concurrency=0, pass READ_BUFFERS_SYNCHRONOUSLY to StartReadBuffers() to ensure synchronous IO executionThere are further improvements we should consider:- While in read_stream_look_ahead(), we can use AIO batch submission mode for increased efficiency. That however requires care to avoid deadlocks and thus done separately.- It can be beneficial to defer starting new IOs until we can issue multiple IOs at once. That however requires non-trivial heuristics to decide when to do so.Reviewed-by: Noah Misch <noah@leadboat.com>Co-authored-by: Andres Freund <andres@anarazel.de>Co-authored-by: Thomas Munro <thomas.munro@gmail.com>
1 parentb27f863 commitf4d0730

File tree

1 file changed

+26
-13
lines changed

1 file changed

+26
-13
lines changed

‎src/backend/storage/aio/read_stream.c

Lines changed: 26 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -72,6 +72,7 @@
7272
#include"postgres.h"
7373

7474
#include"miscadmin.h"
75+
#include"storage/aio.h"
7576
#include"storage/fd.h"
7677
#include"storage/smgr.h"
7778
#include"storage/read_stream.h"
@@ -99,6 +100,8 @@ struct ReadStream
99100
int16pinned_buffers;
100101
int16distance;
101102
int16initialized_buffers;
103+
intread_buffers_flags;
104+
boolsync_mode;/* using io_method=sync */
102105
booladvice_enabled;
103106
booltemporary;
104107

@@ -250,7 +253,7 @@ read_stream_start_pending_read(ReadStream *stream)
250253
Assert(stream->next_buffer_index==stream->oldest_buffer_index);
251254

252255
/* Do we need to issue read-ahead advice? */
253-
flags=0;
256+
flags=stream->read_buffers_flags;
254257
if (stream->advice_enabled)
255258
{
256259
if (stream->pending_read_blocknum==stream->seq_blocknum)
@@ -261,7 +264,7 @@ read_stream_start_pending_read(ReadStream *stream)
261264
* then stay of the way of the kernel's own read-ahead.
262265
*/
263266
if (stream->seq_until_processed!=InvalidBlockNumber)
264-
flags=READ_BUFFERS_ISSUE_ADVICE;
267+
flags|=READ_BUFFERS_ISSUE_ADVICE;
265268
}
266269
else
267270
{
@@ -272,7 +275,7 @@ read_stream_start_pending_read(ReadStream *stream)
272275
*/
273276
stream->seq_until_processed=stream->pending_read_blocknum;
274277
if (stream->pinned_buffers>0)
275-
flags=READ_BUFFERS_ISSUE_ADVICE;
278+
flags|=READ_BUFFERS_ISSUE_ADVICE;
276279
}
277280
}
278281

@@ -613,27 +616,33 @@ read_stream_begin_impl(int flags,
613616
stream->per_buffer_data= (void*)
614617
MAXALIGN(&stream->ios[Max(1,max_ios)]);
615618

619+
stream->sync_mode=io_method==IOMETHOD_SYNC;
620+
616621
#ifdefUSE_PREFETCH
617622

618623
/*
619-
*This system supports prefetchingadvice. We can use it as long as
620-
* direct I/O isn't enabled, the caller hasn't promised sequential access
621-
*(overriding our detection heuristics), and max_ioshasn'tbeen set to
622-
* zero.
624+
*Read-aheadadvice simulating asynchronous I/O with synchronous calls.
625+
*Issue advice only if AIO is not used,direct I/O isn't enabled, the
626+
*callerhasn'tpromised sequential access (overriding our detection
627+
*heuristics), and max_ios hasn't been set tozero.
623628
*/
624-
if ((io_direct_flags&IO_DIRECT_DATA)==0&&
629+
if (stream->sync_mode&&
630+
(io_direct_flags&IO_DIRECT_DATA)==0&&
625631
(flags&READ_STREAM_SEQUENTIAL)==0&&
626632
max_ios>0)
627633
stream->advice_enabled= true;
628634
#endif
629635

630636
/*
631-
*For now,max_ios= 0 is interpreted as max_ios = 1 with advice disabled
632-
*above. If we had real asynchronousI/O we might need a slightly
633-
*different definition.
637+
*Settingmax_iosto zero disables AIO and advice-based pseudo AIO, but
638+
*we still need to allocate space to combine and run oneI/O. Bump it up
639+
*to one, and remember to ask for synchronous I/O only.
634640
*/
635641
if (max_ios==0)
642+
{
636643
max_ios=1;
644+
stream->read_buffers_flags=READ_BUFFERS_SYNCHRONOUSLY;
645+
}
637646

638647
/*
639648
* Capture stable values for these two GUC-derived numbers for the
@@ -777,6 +786,11 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data)
777786

778787
if (likely(next_blocknum!=InvalidBlockNumber))
779788
{
789+
intflags=stream->read_buffers_flags;
790+
791+
if (stream->advice_enabled)
792+
flags |=READ_BUFFERS_ISSUE_ADVICE;
793+
780794
/*
781795
* Pin a buffer for the next call. Same buffer entry, and
782796
* arbitrary I/O entry (they're all free). We don't have to
@@ -792,8 +806,7 @@ read_stream_next_buffer(ReadStream *stream, void **per_buffer_data)
792806
if (likely(!StartReadBuffer(&stream->ios[0].op,
793807
&stream->buffers[oldest_buffer_index],
794808
next_blocknum,
795-
stream->advice_enabled ?
796-
READ_BUFFERS_ISSUE_ADVICE :0)))
809+
flags)))
797810
{
798811
/* Fast return. */
799812
returnbuffer;

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp