Horton

Re: MultiXact\SLRU buffers configuration

x4mmm@yandex-team.ru

View thread View on postgr.es
From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Gilles Darold <gilles@darold.net>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alexander Korotkov <aekorotkov@gmail.com>, Anastasia Lubennikova <a.lubennikova@postgrespro.ru>, Daniel Gustafsson <daniel@yesql.se>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-04-08T07:24:55Z
Lists: pgsql-hackers 

> 8 апр. 2021 г., в 03:30, Thomas Munro <thomas.munro@gmail.com> написал(а):
> 
> Here's another approach that is a little less exciting than
> "tournament RR" (or whatever that should be called; I couldn't find an
> established name for it).  This version is just our traditional linear
> search, except that it stops at 128, and remembers where to start from
> next time (like a sort of Fisher-Price GCLOCK hand).  This feels more
> committable to me.  You can argue that all buffers above 128 are bonus
> buffers that PostgreSQL 13 didn't have, so the fact that we can no
> longer find the globally least recently used page when you set
> xact_buffers > 128 doesn't seem too bad to me, as an incremental step
> (but to be clear, of course we can do better than this with more work
> in later releases).
I agree that this version of eviction seems much more effective and less intrusive than RR. And it's still LRU, which is important for subsystem that is called SLRU.
shared->search_slotno is initialized implicitly with memset(). But this seems like a common practice.
Also comment above "max_search = Min(shared->num_slots, MAX_REPLACEMENT_SEARCH);" does not reflect changes.

Besides this patch looks good to me.

Thanks!

Best regards, Andrey Borodin.

Commits

  1. Rework new SLRU test with injection points

  2. injection_point: Add injection_points.stats

  3. injection_points: Add initialization of shmem state when loading module

  4. Add injection-point test for new multixact CV usage

  5. Use conditional variable to wait for next MultiXact offset

  6. Improve performance of subsystems on top of SLRU

  7. Adjust VACUUM hastup LP_REDIRECT comments.

  8. Test replay of regression tests, attempt II.