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Re: WIP: WAL prefetch (another approach)

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Thomas Munro <thomas.munro@gmail.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@postgresql.org
Date: 2021-04-09T20:36:58Z
Lists: pgsql-hackers 
On Sat, Apr 10, 2021 at 08:27:42AM +1200, Thomas Munro wrote:
> 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].

Yes, I have it in my list for v14 deployment.  Thanks for that.

Did you see this?
https://www.postgresql.org/message-id/GV0P278MB0483490FEAC879DCA5ED583DD2739%40GV0P278MB0483.CHEP278.PROD.OUTLOOK.COM

I meant to mail you so you could include it in the same commit, but forgot
until now.

-- 
Justin

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