Re: Move PinBuffer and UnpinBuffer to atomics

From: Andres Freund <andres(at)anarazel(dot)de>
To: Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, YUriy Zhuravlev <u(dot)zhuravlev(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Move PinBuffer and UnpinBuffer to atomics
Date: 2016-03-31 12:22:30
Message-ID: 20160331122230.zu5hpo3pzlkyutr5@alap3.anarazel.de
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On 2016-03-31 12:58:55 +0200, Andres Freund wrote:
> On 2016-03-31 06:54:02 -0400, Robert Haas wrote:
> > On Wed, Mar 30, 2016 at 3:16 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > > Yea, as Tom pointed out that's not going to work. I'll try to write a
> > > patch for approach 1).
> >
> > Does this mean that any platform that wants to perform well will now
> > need a sub-4-byte spinlock implementation? That's has a somewhat
> > uncomfortable sound to it.
>
> Oh. I confused my approaches. I was thinking about going for 2):
>
> > 2) Replace the lwlock spinlock by a bit in LWLock->state. That'd avoid
> > embedding the spinlock, and actually might allow to avoid one atomic
> > op in a number of cases.
>
> precisely because of that concern.

Here's a WIP patch to evaluate. Dilip/Ashutosh, could you perhaps run
some benchmarks, to see whether this addresses the performance issues?

I guess it'd both be interesting to compare master with master + patch,
and this thread's latest patch with the patch additionally applied.

Thanks!

Andres

Attachment Content-Type Size
0001-WIP-Avoid-the-use-of-a-separate-spinlock-to-protect-.patch text/x-patch 10.0 KB

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