From: Tomas Vondra <tv@fuzzy.cz>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Checkpoints and slow queries
Date: Mon, 28 Apr 2014 23:19:08 +0200
Message-ID: <535EC5CC.5090504@fuzzy.cz> (raw)
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On 28.4.2014 22:54, Jeff Janes wrote:
> On Mon, Apr 28, 2014 at 1:41 PM, Tomas Vondra <tv@fuzzy.cz
> There's certainly something fishy, because although this is the supposed
> configuration:
>
> checkpoint_segments = 250
> checkpoint_timeout = 1h
> checkpoint_completion_target = 0.9
>
> the checkpoint logs typically finish in much shorter periods of time.
>
> That doesn't look fishy to me. The checkpointer will not take more than
> one nap between buffers, so it will always write at least 10 buffers per
> second (of napping time) even if that means it finishes early. Which
> seems to be the case here--the length of the write cycle seems to be
> about one tenth the number of buffers written.
Oh, makes sense I guess. Apparently I'm tuning this only on systems
doing a lot of I/O, so this behaviour somehow escaped me.
Tomas
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To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz, jeff.janes@gmail.com
Subject: Re: Checkpoints and slow queries
In-Reply-To: <535EC5CC.5090504@fuzzy.cz>
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