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From: Josh Berkus <josh@agliodbs.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: High CPU usage / load average after upgrading to Ubuntu 12.04
Date: Wed, 20 Feb 2013 14:44:34 -0800
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On 02/19/2013 07:15 PM, Scott Marlowe wrote:
> On Tue, Feb 19, 2013 at 4:24 PM, Josh Berkus <josh@agliodbs.com> wrote:
>> ... then you'll see checkpoint "stalls" and spread checkpoint will
>> actually make them worse by making the stalls longer.
> 
> Wait, if they're spread enough then there won't be a checkpoint, so to
> speak.  Are you saying that spreading them out means that they still
> kind of pile up, even with say a completion target of 1.0 etc?

I'm saying that spreading them makes things worse, because they get
intermixed with the fsyncs for the WAL and causes commits to stall.  I
tried setting checkpoint_completion_target = 0.0 and throughput got
about 10% better.

I'm beginning to think that checkpoint_completion_target should be 0.0,
by default.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com


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