Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933179Ab0HELdd (ORCPT ); Thu, 5 Aug 2010 07:33:33 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:40286 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754858Ab0HELdb (ORCPT ); Thu, 5 Aug 2010 07:33:31 -0400 Date: Thu, 5 Aug 2010 07:32:40 -0400 From: Chris Mason To: Dominik Brodowski , Valdis.Kletnieks@vt.edu, josef@redhat.com, Michael Monnerie , Christoph Hellwig , linux-raid@vger.kernel.org, xfs@oss.sgi.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: Re: direct-io regression [Was: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs] Message-ID: <20100805113240.GA29846@think> Mail-Followup-To: Chris Mason , Dominik Brodowski , Valdis.Kletnieks@vt.edu, josef@redhat.com, Michael Monnerie , Christoph Hellwig , linux-raid@vger.kernel.org, xfs@oss.sgi.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com References: <20100804073546.GA7494@comet.dominikbrodowski.net> <20100804085039.GA11671@infradead.org> <20100804091317.GA27779@isilmar-3.linta.de> <20100804092122.GA2998@infradead.org> <20100804073546.GA7494@comet.dominikbrodowski.net> <201008041116.09822@zmi.at> <20100804102526.GB13766@isilmar-3.linta.de> <15446.1280953986@localhost> <20100805093100.GA3001@comet.dominikbrodowski.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100805093100.GA3001@comet.dominikbrodowski.net> User-Agent: Mutt/1.5.20 (2009-06-14) X-Source-IP: acsmt354.oracle.com [141.146.40.154] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090209.4C5AA172.016F:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1493 Lines: 41 On Thu, Aug 05, 2010 at 11:31:00AM +0200, Dominik Brodowski wrote: > Hey, > > when attempting to track down insufficient I/O performance, I found the > following reression relating to direct-io on my notebook, where an > ata device, which consists of several partitions, is combined to a lvm > volume, and one logical volume is then encrypted using dm-crypt. Test case > was the following command: > > $ dd if=/dev/mapper/vg0-root_crypt of=/dev/zero iflag=direct bs=8k count=131072 > > 2.6.34 results in ~16 MB/s, > 2.6.35 results in ~ 3.1 MB/s > > The regression was bisected down to the follwoing commit: > > commit c2c6ca417e2db7a519e6e92c82f4a933d940d076 > Author: Josef Bacik > Date: Sun May 23 11:00:55 2010 -0400 > > direct-io: do not merge logically non-contiguous requests > > ... > > How to fix this? I do not use btrfs, but ext3 (and the access was down on > the block level, not on the fs level, so this btrs-related commit should not > cause such a regression). Well, you've already bisected down to an offending if statement, that's a huge help. I'll try to reproduce this and fix it up today. But, I'm surprised your drive is doing 8K dio reads at 16MB/s, that seems a little high. -chris -- 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/