Re: postgresql latency & bgwriter not doing its job

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: postgresql latency & bgwriter not doing its job
Date: 2014-08-27 09:19:22
Message-ID: 20140827091922.GD21544@awork2.anarazel.de
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On 2014-08-27 11:14:46 +0200, Andres Freund wrote:
> On 2014-08-27 11:05:52 +0200, Fabien COELHO wrote:
> > I can test a couple of patches. I already did one on someone advice (make
> > bgwriter round all stuff in 1s instead of 120s, without positive effect.
>
> I've quickly cobbled together the attached patch (which at least doesn't
> seem to crash & burn). It tries to trigger pages being flushed out
> during the paced phase of checkpoints instead of the fsync phase. The
> sync_on_checkpoint_flush can be used to enable/disable that behaviour.
>
> I'd be interested to hear whether that improves your latency numbers. I
> unfortunately don't have more time to spend on this right now :(.

And actually attached. Note that it's linux only...

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

Attachment Content-Type Size
force-flush-during-buffer-sync.diff text/x-diff 10.4 KB

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