X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id 3BF5752A99 for ; Fri, 8 Jul 2005 14:48:34 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 58872-09 for ; Fri, 8 Jul 2005 17:48:24 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id DD48852A79 for ; Fri, 8 Jul 2005 14:48:23 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id j68HmMi8024554; Fri, 8 Jul 2005 13:48:22 -0400 (EDT) To: Ian Westmacott Cc: pgsql-performance@postgresql.org Subject: Re: cost-based vacuum In-reply-to: <1120839902.20657.197.camel@spectre.intellivid.com> References: <1120839902.20657.197.camel@spectre.intellivid.com> Comments: In-reply-to Ian Westmacott message dated "Fri, 08 Jul 2005 12:25:02 -0400" Date: Fri, 08 Jul 2005 13:48:22 -0400 Message-ID: <24553.1120844902@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 tagged_above=0 required=5 tests=AWL X-Spam-Level: X-Archive-Number: 200507/92 X-Sequence-Number: 13333 Ian Westmacott writes: > If I make the single configuration change of setting > vacuum_cost_delay=1000, each iteration in analyze_thread takes > much longer, of course. But what I also see is that the CPU > usage of the connections for writer_thread and reader_thread > spike up to well over 80% each (this is a dualie) and latency > drops to 8-10s, during the ANALYZEs. [ scratches head... ] That doesn't make any sense at all. > I don't understand why this would be. I don't think there > are any lock issues, and I don't see any obvious I/O issues. > Am I missing something? Is there any way to get some > insight into what those connections are doing? Profiling maybe? Can you put together a self-contained test case that replicates this behavior, so other people could look? regards, tom lane