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Re: WIP: WAL prefetch (another approach)

Tomas Vondra <tomas.vondra@2ndquadrant.com>

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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Stephen Frost <sfrost@snowman.net>, Dmitry Dolgov <9erthalion6@gmail.com>, David Steele <david@pgmasters.net>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-08-06T10:47:01Z
Lists: pgsql-hackers 
On Thu, Aug 06, 2020 at 02:58:44PM +1200, Thomas Munro wrote:
>On Tue, Aug 4, 2020 at 3:47 AM Tomas Vondra
><tomas.vondra@2ndquadrant.com> wrote:
>> On Thu, Jul 02, 2020 at 03:09:29PM +1200, Thomas Munro wrote:
>> >FYI I am still trying to reproduce and understand the problem Tomas
>> >reported; more soon.
>>
>> Any luck trying to reproduce thigs? Should I try again and collect some
>> additional debug info?
>
>No luck.  I'm working on it now, and also trying to reduce the
>overheads so that we're not doing extra work when it doesn't help.
>

OK, I'll see if I can still reproduce it.

>By the way, I also looked into recovery I/O stalls *other* than
>relation buffer cache misses, and created
>https://commitfest.postgresql.org/29/2669/ to fix what I found.  If
>you avoid both kinds of stalls then crash recovery is finally CPU
>bound (to go faster after that we'll need parallel replay).

Yeah, I noticed. I'll take a look and do some testing in the next CF.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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