From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993214AbXDSJMl (ORCPT ); Thu, 19 Apr 2007 05:12:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2993226AbXDSJMl (ORCPT ); Thu, 19 Apr 2007 05:12:41 -0400 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:45919 "EHLO ecfrec.frec.bull.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993211AbXDSJMk (ORCPT ); Thu, 19 Apr 2007 05:12:40 -0400 Message-ID: <46273251.4000403@bull.net> Date: Thu, 19 Apr 2007 11:11:45 +0200 From: Valerie Clement User-Agent: Thunderbird 1.5.0.4 (Windows/20060516) MIME-Version: 1.0 To: Andrew Morton Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Performance degradation with FFSB between 2.6.20 and 2.6.21-rc7 References: <462622F8.10107@bull.net> <20070418135709.b499e050.akpm@linux-foundation.org> In-Reply-To: <20070418135709.b499e050.akpm@linux-foundation.org> X-MIMETrack: Itemize by SMTP Server on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 19/04/2007 11:15:10, Serialize by Router on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 19/04/2007 11:15:12, Serialize complete at 19/04/2007 11:15:12 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > It could be due to I/O scheduler changes. Which one are you using? CFQ? > > Or it could be that there has been some changed behaviour at the VFS/pagecache > layer: the VFS might be submitting little hunks of lots of files, rather than > large hunks of few files. > > Or it could be a block-layer thing: perhaps some driver change has caused > us to be placing less data into the queue. Which device driver is that machine > using? > > Being a simple soul, the first thing I'll try when I get near a test box > will be > > for i in $(seq 1 16) > do > time dd if=/dev/zero of=$i bs=1M count=1024 & > done > I tried first the test with dd, the results are similar to those of FFSB tests, about 15 percent of degradation between 2.6.20.7 and 2.6.21-rc7. I'm using the CFQ I/O scheduler. I changed it to the "deadline" one and I don't have any more the problem, I've got similar throughput values with 2.6.20.7 and 2.6.21-rc7 kernels. So can we conclude that it's due to the CFQ scheduler? I also checked the device driver used, the revision number is the same in 2.6.20 and 2.6.21. Valérie