Re: Performance degradation in commit ac1d794

From: Andres Freund <andres(at)anarazel(dot)de>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Васильев Дмитрий <d(dot)vasilyev(at)postgrespro(dot)ru>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance degradation in commit ac1d794
Date: 2016-03-18 18:30:58
Message-ID: 20160318183058.duh2lih2me66ynrp@alap3.anarazel.de
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On 2016-03-18 20:14:07 +0530, Amit Kapila wrote:
> + * from inside a signal handler in latch_sigusr1_handler().
>
> *
>
> * Note: we assume that the kernel calls involved in drainSelfPipe()
>
> * and SetLatch() will provide adequate synchronization on machines
>
> * with weak memory ordering, so that we cannot miss seeing is_set if
>
> * the signal byte is already in the pipe when we drain it.
>
> */
>
> - drainSelfPipe();
>
> -
>
>
> Above part of comment looks redundant after this patch.

Don't think so. Moving it closer to the drainSelfPipe() call might be
neat, but since there's several callsites...

> I have done some
> tests on Windows with 0003 patch which includes running the regressions
> (vcregress check) and it passes. Will look into it tomorrow once again and
> share if I find anything wrong with it, but feel to proceed if you want.

Thanks for the testing thus far! Let's see what the buildfarm has to
say.

Andres

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