From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Dunstan <andrew.dunstan@pgexperts.com>
cc: pgsql-perform <pgsql-performance@postgresql.org>
Subject: Re: backend suddenly becomes slow, then remains slow
In-reply-to: <50CB7284.3020008@pgexperts.com>
References: <50CB7284.3020008@pgexperts.com>
Comments: In-reply-to Andrew Dunstan <andrew.dunstan@pgexperts.com>
	message dated "Fri, 14 Dec 2012 13:40:04 -0500"
Date: Fri, 14 Dec 2012 14:56:00 -0500
Message-ID: <5309.1355514960@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

Andrew Dunstan <andrew.dunstan@pgexperts.com> writes:
> One of my clients has an odd problem. Every so often a backend will 
> suddenly become very slow. The odd thing is that once this has happened 
> it remains slowed down, for all subsequent queries. Zone reclaim is off. 
> There is no IO or CPU spike, no checkpoint issues or stats timeouts, no 
> other symptom that we can see. The problem was a lot worse that it is 
> now, but two steps have alleviated it mostly, but not completely: much 
> less aggressive autovacuuming and reducing the maximum lifetime of 
> backends in the connection pooler to 30 minutes.

> It's got us rather puzzled. Has anyone seen anything like this?

Maybe the kernel is auto-nice'ing the process once it's accumulated X
amount of CPU time?

			regards, tom lane


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