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Re: WIP: WAL prefetch (another approach)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Andres Freund <andres@anarazel.de>, Stephen Frost <sfrost@snowman.net>, Alvaro Herrera <alvherre@2ndquadrant.com>, David Steele <david@pgmasters.net>, Dmitry Dolgov <9erthalion6@gmail.com>, Jakub Wartak <Jakub.Wartak@tomtom.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-05-04T13:46:12Z
Lists: pgsql-hackers 
Tomas Vondra <tomas.vondra@enterprisedb.com> writes:
> On 5/3/21 7:42 AM, Thomas Munro wrote:
>> Hmm, yeah that does seem plausible.  It would be nice to see a report
>> from any other system though.  I'm still trying, and reviewing...

> FWIW I've ran the test (make installcheck-parallel in a loop) on four 
> different machines - two x86_64 ones, and two rpi4. The x86 boxes did 
> ~1000 rounds each (and one of them had 5 local replicas) without any 
> issue. The rpi4 machines did ~50 rounds each, also without failures.

Yeah, I have also spent a fair amount of time trying to reproduce it
elsewhere, without success so far.  Notably, I've been trying on a
PPC Mac laptop that has a fairly similar CPU to what's in the G4,
though a far slower disk drive.  So that seems to exclude theories
based on it being PPC-specific.

I suppose that if we're unable to reproduce it on at least one other box,
we have to write it off as hardware flakiness.  I'm not entirely
comfortable with that answer, but I won't push for reversion of the WAL
patches without more evidence that there's a real issue.

			regards, tom lane

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix recovery_prefetch docs.

  2. Prefetch data referenced by the WAL, take II.

  3. Add circular WAL decoding buffer, take II.

  4. Fix generation of ./INSTALL for the distribution tarball

  5. Revert recovery prefetching feature.

  6. Sync guc.c and postgresql.conf.sample with the SGML docs.

  7. Add information of total data processed to replication slot stats.

  8. Doc: Review for "Optionally prefetch referenced data in recovery."

  9. Add circular WAL decoding buffer.

  10. Optionally prefetch referenced data in recovery.

  11. Remove read_page callback from XLogReader.

  12. Provide ReadRecentBuffer() to re-pin buffers by ID.

  13. Provide recovery_init_sync_method=syncfs.

  14. Mark factorial operator, and postfix operators in general, as deprecated.

  15. Rationalize GetWalRcv{Write,Flush}RecPtr().

  16. Support PrefetchBuffer() in recovery.

  17. Prevent hard failures of standbys caused by recycled WAL segments