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Re: WIP: WAL prefetch (another approach)

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Tomas Vondra <tomas.vondra@enterprisedb.com>, Stephen Frost <sfrost@snowman.net>, Andres Freund <andres@anarazel.de>, Jakub Wartak <Jakub.Wartak@tomtom.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Dmitry Dolgov <9erthalion6@gmail.com>, David Steele <david@pgmasters.net>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-04-09T20:27:42Z
Lists: pgsql-hackers 
On Fri, Apr 9, 2021 at 3:37 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
> Here's some little language fixes.

Thanks!  Done.  I rewrote the gibberish comment that made you say
"XXX: what?".  Pushed.

> BTW, before beginning "recovery", PG syncs all the data dirs.
> This can be slow, and it seems like the slowness is frequently due to file
> metadata.  For example, that's an obvious consequence of an OS crash, after
> which the page cache is empty.  I've made a habit of running find /zfs -ls |wc
> to pre-warm it, which can take a little bit, but then the recovery process
> starts moments later.  I don't have any timing measurements, but I expect that
> starting to stat() all data files as soon as possible would be a win.

Did you see commit 61752afb, "Provide
recovery_init_sync_method=syncfs"?  Actually I believe it's safe to
skip that phase completely and do a tiny bit more work during
recovery, which I'd like to work on for v15[1].

[1] https://www.postgresql.org/message-id/flat/CA%2BhUKG%2B8Wm8TSfMWPteMEHfh194RytVTBNoOkggTQT1p5NTY7Q%40mail.gmail.com

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