From: | Michail Nikolaev <michail(dot)nikolaev(at)gmail(dot)com> |
---|---|
To: | Andrey Borodin <x4mmm(at)yandex-team(dot)ru> |
Cc: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, reshkekirill <reshkekirill(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Slow standby snapshot |
Date: | 2022-09-16 16:08:24 |
Message-ID: | CANtu0og4M980=JbtgeWxRZcokmFxGBHYn96Sg+nhaTCoAj6+1A@mail.gmail.com |
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Lists: | pgsql-hackers |
Hello everyone.
To find the best frequency for calling KnownAssignedXidsCompress in
Simon's patch, I made a set of benchmarks. It looks like each 8th xid
is a little bit often.
Setup and method is the same as previous (1). 16-core machines,
max_connections = 5000. Tests were running for about a day, 220 runs
in total (each version for 20 times, evenly distributed throughout the
day).
Staring from 60th second, 30 seconds-long transaction was started on primary.
Graphs in attachment. So, looks like 64 is the best value here. It
gives even a little bit more TPS than smaller values.
Yes, such benchmark does not cover all possible cases, but it is
better to measure at least something when selecting constants :)
If someone has an idea of different benchmark scenarios - please share them.
So, updated version (with 64 and some commit message) in attachment too.
Attachment | Content-Type | Size |
---|---|---|
v8-0001-Currently-KnownAssignedXidsGetAndSetXmin-requires.patch | text/plain | 3.2 KB |
image.png | image/png | 302.3 KB |
image.png | image/png | 180.8 KB |
image/png | 57.0 KB |
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