Message-ID: <5060CAFF.8040203@perathoner.de>
Date: Mon, 24 Sep 2012 23:05:03 +0200
From: Marcello Perathoner <marcello@perathoner.de>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
	rv:10.0.6esrpre) Gecko/20120817 Icedove/10.0.6
MIME-Version: 1.0
To: Dennis Brouwer <dennis.brouwer@m4n.nl>
CC: pgsql-admin@postgresql.org
References: 
 <CAMfP6GYL4Tkga5MKO9=KR5n9Ht_4Nk3Qk4_K0g8Yug09FoJo7g@mail.gmail.com>
In-Reply-To: 
 <CAMfP6GYL4Tkga5MKO9=KR5n9Ht_4Nk3Qk4_K0g8Yug09FoJo7g@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: CPU causes 100% load in user space when ntp client runs
	and postgresql is under heavy load

On 09/24/2012 03:53 PM, Dennis Brouwer wrote:

> Last week I was repeatedly able to run all these tests on the database
> without any issue but recently, all of a sudden at random, some of the
> queries performed a factor 100 less. It may take hours to complete the
> transaction. At the same moment we see a dramatic decrease in IO and the
> CPU is nearly 100% busy in user space.
>
> After days of testing I may have found the cause: the ntp client. If I stop
> the ntp client the problem vanishes.

Any chance you are hitting this known linux bug in conjunction with a 
misconfigured ntp server? ie. does a

  # date -s now

fix the cpu load?


http://blog.mozilla.org/it/2012/06/30/mysql-and-the-leap-second-high-cpu-and-the-fix/comment-page-1/#comment-1471

 
http://serverfault.com/questions/403732/anyone-else-experiencing-high-rates-of-linux-server-crashes-during-a-leap-second


-- 
Marcello Perathoner
webmaster@gutenberg.org