Re: MultiXact\SLRU buffers configuration

From: "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: vignesh C <vignesh21(at)gmail(dot)com>, Andrew Borodin <amborodin86(at)gmail(dot)com>, i(dot)lazarev(at)postgrespro(dot)ru, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Gilles Darold <gilles(at)darold(dot)net>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pgsql-hackers mailing list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: MultiXact\SLRU buffers configuration
Date: 2024-01-28 18:17:16
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> On 28 Jan 2024, at 17:49, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> I'd appreciate it if you or Horiguchi-san can update his patch to remove
> use of usleep in favor of a CV in multixact, and keep this CF entry to
> cover it.

Sure! Sounds great!

> Perhaps a test to make the code reach the usleep(1000) can be written
> using injection points (49cd2b93d7db)?

I've tried to prototype something like that. But interesting point between GetNewMultiXactId() and RecordNewMultiXact() is a critical section, and we cannot have injection points in critical sections...
Also, to implement such a test we need "wait" type of injection points, see step 2 in attachment. With this type of injection points I can stop a backend amidst entering information about new MultiXact.

Best regards, Andrey Borodin.

Attachment Content-Type Size
0001-Add-conditional-variable-to-wait-for-next-MultXact-o.patch application/octet-stream 3.3 KB
0002-Add-wait-type-for-injection-points.patch application/octet-stream 3.7 KB
0003-Try-to-test-multixact-CV-sleep.patch application/octet-stream 5.3 KB

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