Received: from maia.hub.org (unknown [200.46.208.211]) by mail.postgresql.org (Postfix) with ESMTP id 5523463261A for ; Mon, 8 Feb 2010 11:30:37 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.208.211]) (amavisd-maia, port 10024) with ESMTP id 01298-05 for ; Mon, 8 Feb 2010 15:30:00 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.17.8]) by mail.postgresql.org (Postfix) with ESMTP id 59A2A633BE3 for ; Mon, 8 Feb 2010 11:30:26 -0400 (AST) Received: from [192.168.0.105] (pool-96-244-14-10.bltmmd.fios.verizon.net [96.244.14.10]) by mrelayeu.kundenserver.de (node=mrbap1) with ESMTP (Nemesis) id 0LrqPu-1NrJaz0CVy-013U0r; Mon, 08 Feb 2010 16:30:17 +0100 Message-ID: <4B702E05.1000708@2ndquadrant.com> Date: Mon, 08 Feb 2010 10:30:13 -0500 From: Greg Smith User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Kevin Grittner CC: pgsql-performance@postgresql.org, Albe Laurenz Subject: Re: Linux I/O tuning: CFQ vs. deadline References: <4B6FDD26.9010106@2ndquadrant.com> <4B6FD868020000250002F084@gw.wicourts.gov> In-Reply-To: <4B6FD868020000250002F084@gw.wicourts.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V01U2FsdGVkX18h133lzu7RBEKaWN78gRUamfupN/pYcGErXTJ TRXPpEbFjBHG4Df5unMfPlXLb68TYWenQiUnib0WHbabyDp5TB uXlhOcUZd+PJpT00B7wSese8Le+eL2h X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-2.418 tagged_above=-10 required=5 tests=AWL=0.181, BAYES_00=-2.599 X-Spam-Level: X-Archive-Number: 201002/121 X-Sequence-Number: 37542 Kevin Grittner wrote: > I'll keep this in mind as something to try if we have problem > performance in line with what that page describes, though.... > That's basically what I've been trying to make clear all along: people should keep an open mind, watch what happens, and not make any assumptions. There's no clear cut preference for one scheduler or the other in all situations. I've seen CFQ do much better, you and Albe report situations where the opposite is true. I was just happy to see another report of someone running into the same sort of issue I've been seeing, because I didn't have very much data to offer about why the standard advice of "always use deadline for a database app" might not apply to everyone. -- Greg Smith 2ndQuadrant Baltimore, MD PostgreSQL Training, Services and Support greg@2ndQuadrant.com www.2ndQuadrant.com