Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761134AbZJIQpV (ORCPT ); Fri, 9 Oct 2009 12:45:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761122AbZJIQpU (ORCPT ); Fri, 9 Oct 2009 12:45:20 -0400 Received: from james.oetiker.ch ([213.144.138.195]:33415 "EHLO james.oetiker.ch" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752404AbZJIQpT (ORCPT ); Fri, 9 Oct 2009 12:45:19 -0400 Date: Fri, 9 Oct 2009 18:44:12 +0200 (CEST) From: Tobias Oetiker To: linux-kernel@vger.kernel.org Subject: Linux IO service time - a perfect source of randomness ? Message-ID: User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1281 Lines: 38 I have just completed extensive benchmarking of ext3 on 2.6.31.2 both on HW RAID6 as well as single Hard Drive. I have written a new file system benchmark that creates load by reading and writing large file trees in paralle to simulate a busy fileserver. The results are as follows: * as soon as the system comes under strain the service time for single io operations becomes almost random with huge outliers of several seconds. * on HW RAID the best performance is to be gained with data=ordered and cfq scheduler * on single HDD setups, only (!) data=writeback with cfq provides good performance. * the deadline scheduler did not perform well in any of the read/write scenarios. * btrfs has fantastic read performance but does not (yet?) do well when readers and writers are competing. my report is on http://insights.oetiker.ch/linux/fsopbench/ cheers tobi -- Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland http://it.oetiker.ch tobi@oetiker.ch ++41 62 775 9902 / sb: -9900 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/