From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>, Michael Paquier <michael(at)paquier(dot)xyz>, Peter Geoghegan <pg(at)bowt(dot)ie>, Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Re: conchuela timeouts since 2021-10-09 system upgrade |
Date: | 2021-10-27 03:01:44 |
Message-ID: | 20211027030144.GA152505@rfd.leadboat.com |
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On Tue, Oct 26, 2021 at 03:41:58PM -0400, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > On Tue, Oct 26, 2021 at 02:03:54AM -0400, Tom Lane wrote:
> >> Or more
> >> practically, use advisory locks in that script to enforce that only one
> >> runs at once.
>
> > The author did try that.
>
> Ah, I see: if the other pgbench thread is waiting in pg_advisory_lock,
> then it is inside a transaction, so it blocks CIC from completing.
> We can get around that though, by using pg_try_advisory_lock and not
> proceeding if it fails.
Good thought.
> The attached POC does this for the 002 test;
> it looks like the same thing could be done to 003.
>
> Now the problem with this is it will only work back to v12, because
> pgbench lacks the necessary features before that. However, I think
> it's worth doing it like this in versions where we can do so, because
> of the load-balancing aspect: this won't waste cycles running CICs
> after the inserts have stopped, nor vice versa.
>
> Thoughts?
I tried it out with the fix removed (git checkout fdd965d; git checkout HEAD^
src/include src/backend; git apply CIC-test-with-one-pgbench.patch).
Sensitivity (~25%) and runtime (~900ms) were in the same ballpark. Still,
even if it doesn't buy back notable cycles, the test code seems easier to read
and understand with your change.
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