Re: High CPU usage / load average after upgrading to Ubuntu 12.04

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From: Josh Berkus <josh@agliodbs.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: High CPU usage / load average after upgrading to Ubuntu 12.04
Date: Mon, 18 Feb 2013 16:39:53 -0800
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Scott,

> So do you have generally slow IO, or is it fsync behavior etc?

All tests except pgBench show this system as superfast.  Bonnie++ and DD
tests are good (200 to 300mb/s), and test_fsync shows 14K/second.
Basically it has no issues until checkpoint kicks in, at which time the
entire system basically halts for the duration of the checkpoint.

For that matter, if I run a pgbench and halt it just before checkpoint
kicks in, I get around 12000TPS, which is what I'd expect on this system.

At this point, we've tried 3.2.0.26, 3.2.0.27, 3.4.0, and tried updating
the RAID driver, and changing the IO scheduler.  Nothing seems to affect
the behavior.   Testing using Ext4 (instead of XFS) next.


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


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