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Re: [EXTERNAL] Re: WIP: WAL prefetch (another approach)

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Sait Talha Nisanci <Sait.Nisanci@microsoft.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, 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: 2020-08-27T13:51:56Z
Lists: pgsql-hackers 
On Wed, Aug 26, 2020 at 9:42 AM Sait Talha Nisanci
<Sait.Nisanci@microsoft.com> wrote:
> I have tried combination of SSD, HDD, full_page_writes = on/off and max_io_concurrency = 10/50, the recovery times are as follows (in seconds):
>
>                                No prefetch          |     Default prefetch values  |          Default + max_io_concurrency = 50
> SSD, full_page_writes = on      852             301                             197
> SSD, full_page_writes = off     1642            1359                            1391
> HDD, full_page_writes = on      6027            6345                            6390
> HDD, full_page_writes = off     738             275                             192

The regression on HDD with full_page_writes=on is interesting. I don't
know why that should happen, and I wonder if there is anything that
can be done to mitigate it.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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