| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: High CPU usage / load average after upgrading to Ubuntu 12.04 |
| Date: | 2013-02-20 22:44:34 |
| Message-ID: | 512551D2.9090407@agliodbs.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
On 02/19/2013 07:15 PM, Scott Marlowe wrote:
> On Tue, Feb 19, 2013 at 4:24 PM, Josh Berkus <josh(at)agliodbs(dot)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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