Received: from localhost (maia-1.hub.org [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id CA4B79FB4CC for ; Sun, 18 Mar 2007 16:49:40 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-new, port 10024) with ESMTP id 72403-06 for ; Sun, 18 Mar 2007 16:49:37 -0300 (ADT) X-Greylist: delayed 00:59:59.666886 by SQLgrey-1.7.4 Received: from vms048pub.verizon.net (vms048pub.verizon.net [206.46.252.48]) by postgresql.org (Postfix) with ESMTP id BD3369FB3FA for ; Sun, 18 Mar 2007 16:49:37 -0300 (ADT) Received: from osgiliath.mathom.us ([72.66.31.15]) by vms048.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JF400H4H49YL2OH@vms048.mailsrvcs.net> for pgsql-performance@postgresql.org; Sun, 18 Mar 2007 13:49:10 -0500 (CDT) Received: from localhost (localhost [127.0.0.1]) by osgiliath.mathom.us (Postfix) with ESMTP id 59DE170331 for ; Sun, 18 Mar 2007 14:49:08 -0400 (EDT) Received: from osgiliath.mathom.us ([127.0.0.1]) by localhost (osgiliath.home.mathom.us [127.0.0.1]) (amavisd-new, port 10024) with LMTP id Tr2lUE1tLa14 for ; Sun, 18 Mar 2007 14:49:07 -0400 (EDT) Received: by osgiliath.mathom.us (Postfix, from userid 1000) id 1E614712C2; Sun, 18 Mar 2007 14:49:07 -0400 (EDT) Date: Sun, 18 Mar 2007 14:49:06 -0400 From: Michael Stone Subject: Re: Performance Tuning and Disk Cache In-reply-to: <1862C4AD-EB83-4D58-B1F2-45BDC47E5608@genetics.utah.edu> To: pgsql-performance@postgresql.org Mail-followup-to: pgsql-performance@postgresql.org Message-id: <20070318184904.GL25629@mathom.us> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii; format=flowed Content-disposition: inline X-Virus-Scanned: Debian amavisd-new at mathom.us X-Pgp-Fingerprint: 53 FF 38 00 E7 DD 0A 9C 84 52 84 C5 EE DF 7C 88 References: <1862C4AD-EB83-4D58-B1F2-45BDC47E5608@genetics.utah.edu> User-Agent: Mutt/1.5.13 (2006-08-11) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200703/271 X-Sequence-Number: 23676 On Sun, Mar 18, 2007 at 06:45:34AM -0600, Barry Moore wrote: >Does anyone know how I can repeatedly run the same query in the >"worst case scenario" of no postgres data in the disk cache (e.g., >clear the page cache or force it to be ignored)? Depends on your OS. On linux you can run: echo 1 > /proc/sys/vm/drop_caches Mike Stone