Horton

Re: MultiXact\SLRU buffers configuration

Gilles DAROLD <gilles@darold.net>

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From: Gilles Darold <gilles@darold.net>
To: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: 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: 2020-12-10T14:45:56Z
Lists: pgsql-hackers

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Le 08/12/2020 à 18:52, Andrey Borodin a écrit :
> Hi Gilles!
>
> Many thanks for your message!
>
>> 8 дек. 2020 г., в 21:05, Gilles Darold <gilles@darold.net> написал(а):
>>
>> I know that this report is not really helpful
> Quite contrary - this benchmarks prove that controllable reproduction exists. I've rebased patches for PG11. Can you please benchmark them (without extending SLRU)?
>
> Best regards, Andrey Borodin.
>
Hi,


Running tests yesterday with the patches has reported log of failures 
with error on INSERT and UPDATE statements:


    ERROR:  lock MultiXactOffsetControlLock is not held


After a patch review this morning I think I have found what's going 
wrong. In patch 
v6-0001-Use-shared-lock-in-GetMultiXactIdMembers-for-offs.patch I think 
there is a missing reinitialisation of the lockmode variable to LW_NONE 
inside the retry loop after the call to LWLockRelease() in 
src/backend/access/transam/multixact.c:1392:GetMultiXactIdMembers(). 
I've attached a new version of the patch for master that include the fix 
I'm using now with PG11 and with which everything works very well now.


I'm running more tests to see the impact on the performances to play 
with multixact_offsets_slru_buffers, multixact_members_slru_buffers and 
multixact_local_cache_entries. I will reports the results later today.

-- 
Gilles Darold
http://www.darold.net/

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.