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Subject: Re: MultiXact\SLRU buffers configuration
From: Andrey Borodin <x4mmm@yandex-team.ru>
In-Reply-To: <35862787-8b4d-a290-789e-6e12dc6527e8@enterprisedb.com>
Date: Fri, 13 Nov 2020 16:49:36 +0500
Cc: 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>
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References: <a7f1c4e1-1015-92a4-2bd4-6736bd13d03e@postgrespro.ru>
 <2087E87D-44CA-4443-8E6A-5087F07443F4@yandex-team.ru>
 <CAPpHfduekT=BrM3rLqvo4ajzKYmDk+6aCoYJrNHhK0Je+v2z=Q@mail.gmail.com>
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 <CAPpHfdsUtSGxRrKn65F_wrE66sNztNY4TpDGDHh2kvAZZDOMqA@mail.gmail.com>
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 <20201028233243.ygm6yqlynkqpzekr@development>
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To: Tomas Vondra <tomas.vondra@enterprisedb.com>
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> 10 =D0=BD=D0=BE=D1=8F=D0=B1. 2020 =D0=B3., =D0=B2 23:07, Tomas Vondra =
<tomas.vondra@enterprisedb.com> =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB=
(=D0=B0):
>=20
> On 11/10/20 7:16 AM, Andrey Borodin wrote:
>>=20
>>=20
>> but this picture was not stable.
>>=20
>=20
> Seems we haven't made much progress in reproducing the issue :-( I =
guess
> we'll need to know more about the machine where this happens. Is there
> anything special about the hardware/config? Are you monitoring size of
> the pg_multixact directory?

It's Ubuntu 18.04.4 LTS, Intel Xeon E5-2660 v4, 56 CPU cores with 256Gb =
of RAM.
PostgreSQL 10.14, compiled by gcc 7.5.0, 64-bit

No, unfortunately we do not have signals for SLRU sizes.
3.5Tb mdadm raid10 over 28 SSD drives, 82% full.

First incident triggering investigation was on 2020-04-19, at that time =
cluster was running on PG 10.11. But I think it was happening before.

I'd say nothing special...

>=20
>> How do you collect wait events for aggregation? just insert into some =
table with cron?
>>=20
>=20
> No, I have a simple shell script (attached) sampling data from
> pg_stat_activity regularly. Then I load it into a table and aggregate =
to
> get a summary.

Thanks!

Best regards, Andrey Borodin.