Received: from localhost (unknown [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 20C5C2E3725 for ; Wed, 16 Jan 2008 06:50:34 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 00624-01 for ; Wed, 16 Jan 2008 06:50:24 -0400 (AST) Received: from ptb-relay03.plus.net (ptb-relay03.plus.net [212.159.14.214]) by postgresql.org (Postfix) with ESMTP id 7E8A92E3235 for ; Wed, 16 Jan 2008 06:50:27 -0400 (AST) Received: from [84.51.143.99] (helo=server3.office.archonet.com) by ptb-relay03.plus.net with esmtp (Exim) id 1JF5qi-0000Iz-8O; Wed, 16 Jan 2008 10:50:24 +0000 Received: from [192.168.1.36] (dell36.office.archonet.com [192.168.1.36]) by server3.office.archonet.com (Postfix) with ESMTP id 01F35274073; Wed, 16 Jan 2008 10:50:24 +0000 (GMT) Message-ID: <478DE16F.50308@archonet.com> Date: Wed, 16 Jan 2008 10:50:23 +0000 From: Richard Huxton User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Adrian Moisey CC: pgsql-performance@postgresql.org Subject: Re: strange pauses References: <478DDF83.8070106@careerjunction.co.za> In-Reply-To: <478DDF83.8070106@careerjunction.co.za> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200801/132 X-Sequence-Number: 28371 Adrian Moisey wrote: > > If I tail the logs, I see a steady stream of functions that took longer > then 5 seconds. But every now and then I see nothing for 3 minutes and > after that a whole bunch (about 20 - 30) queries all finishing at the > same second. Search this list for references to "checkpoints". If you run vmstat/iostat for a bit you should see bursts of disk activity at those times. Counter-intuitively you probably want *more* checkpoints (with less data to write out each time), but see the list archives for discussion. Also check the manuals for some background info. HTH -- Richard Huxton Archonet Ltd