From: | Stephen Frost <sfrost(at)snowman(dot)net> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Excessive PostmasterIsAlive calls slow down WAL redo |
Date: | 2018-04-06 11:39:28 |
Message-ID: | 20180406113928.GM27724@tamriel.snowman.net |
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Lists: | pgsql-hackers |
Greetings,
* Andres Freund (andres(at)anarazel(dot)de) wrote:
> On 2018-04-05 14:39:27 -0400, Tom Lane wrote:
> > Andres Freund <andres(at)anarazel(dot)de> writes:
> > > ISTM the better approach would be to try to reduce the cost of
> > > PostmasterIsAlive() on common platforms - it should be nearly free if
> > > done right.
> >
> > +1 if it's doable.
[...]
> > While it's not POSIX, at least some platforms are capable of delivering
> > a separate signal on parent process death. Perhaps using that where
> > available would be enough of an answer.
>
> Yea, that'd work on linux. Which is probably the platform 80-95% of
> performance critical PG workloads run on. There's
> JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE on windows, which might also work,
> but I'm not sure it provides enough opportunity for cleanup.
While I tend to agree that it'd be nice to just make it cheaper, that
doesn't seem like something that we'd be likely to back-patch and I tend
to share Heikki's feelings that this is a performance regression we
should be considering fixing in released versions.
What Alvaro posted up-thread seems like it might be a small enough
change to still be reasonable to back-patch and we can still think about
ways to make PostmasterIsAlive() cheaper in the future.
Thanks!
Stephen
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