| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> |
| Cc: | Michail Nikolaev <michail(dot)nikolaev(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, reshkekirill <reshkekirill(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Slow standby snapshot |
| Date: | 2022-11-22 16:53:49 |
| Message-ID: | 3462368.1669136029@sss.pgh.pa.us |
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Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> writes:
> On Tue, 22 Nov 2022 at 16:28, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> If we do those things, do we need a wasted-work counter at all?
> The wasted work counter works well to respond to heavy read-only
> traffic and also avoids wasted compressions for write-heavy workloads.
> So I still like it the best.
This argument presumes that maintenance of the counter is free,
which it surely is not. I don't know how bad contention on that
atomically-updated variable could get, but it seems like it could
be an issue when lots of processes are acquiring snapshots.
regards, tom lane
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