Received: from localhost (unknown [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 03B0F2E3EC2 for ; Wed, 16 Jan 2008 11:23:20 -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 21316-08 for ; Wed, 16 Jan 2008 11:23:07 -0400 (AST) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 91EA32E376B for ; Wed, 16 Jan 2008 11:23:13 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.1/8.14.1) with ESMTP id m0GFN6dV023694; Wed, 16 Jan 2008 10:23:06 -0500 (EST) To: Richard Huxton cc: Adrian Moisey , pgsql-performance@postgresql.org Subject: Re: strange pauses In-reply-to: <478DE16F.50308@archonet.com> References: <478DDF83.8070106@careerjunction.co.za> <478DE16F.50308@archonet.com> Comments: In-reply-to Richard Huxton message dated "Wed, 16 Jan 2008 10:50:23 +0000" Date: Wed, 16 Jan 2008 10:23:06 -0500 Message-ID: <23693.1200496986@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200801/133 X-Sequence-Number: 28372 Richard Huxton writes: > 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. A different line of thought is that something is taking out an exclusive lock on a table that all these queries need. If vmstat doesn't show any burst of activity during these pauses, look into pg_locks. regards, tom lane