From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Thu, 21 Aug 2008 19:23:49 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m7M2NiwF027943 for ; Thu, 21 Aug 2008 19:23:44 -0700 Received: from ipmail01.adl6.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 978C23BF03B for ; Thu, 21 Aug 2008 19:25:04 -0700 (PDT) Received: from ipmail01.adl6.internode.on.net (ipmail01.adl6.internode.on.net [203.16.214.146]) by cuda.sgi.com with ESMTP id PXA0wAJNdLhgjFGy for ; Thu, 21 Aug 2008 19:25:04 -0700 (PDT) Date: Fri, 22 Aug 2008 12:24:59 +1000 From: Dave Chinner Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system) Message-ID: <20080822022459.GL5706@disturbed> References: <200808201613.AA00212@capsicum.lab.ntt.co.jp> <20080820143916.1a7eddab.akpm@linux-foundation.org> <20080821021259.GA5706@disturbed> <20080821051508.GB5706@disturbed> <20080821060418.GC5706@disturbed> <20080821082532.GE5706@disturbed> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Szabolcs Szakacsits Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com On Thu, Aug 21, 2008 at 08:33:50PM +0300, Szabolcs Szakacsits wrote: > > On Thu, 21 Aug 2008, Szabolcs Szakacsits wrote: > > On Thu, 21 Aug 2008, Dave Chinner wrote: > > > On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote: > > > > > > > > One thing I just found out - my old *laptop* is 4-5x faster than the > > > > 10krpm scsi disk behind an old cciss raid controller. I'm wondering > > > > if the long delays in dispatch is caused by an interaction with CTQ > > > > but I can't change it on the cciss raid controllers. Are you using > > > > ctq/ncq on your machine? > > > > It's a laptop and has NCQ. It makes no difference if NCQ is enabled or > > disabled. The problem seems to be XFS only. > > The 'nobarrier' mount option made a big improvement: > > MB/s Runtime (s) > ----- ----------- > btrfs unstable 17.09 572 > ext3 13.24 877 > btrfs 0.16 12.33 793 > nilfs2 2nd+ runs 11.29 674 > ntfs-3g 8.55 865 > reiserfs 8.38 966 > xfs nobarrier 7.89 949 > nilfs2 1st run 4.95 3800 > xfs 1.88 3901 INteresting. Barriers make only a little difference on my laptop; 10-20% slower. But yes, barriers will have this effect on XFS. If you've got NCQ, then you'd do better to turn off write caching on the drive, turn off barriers and use NCQ to give you back the performance that the write cache used to. That is, of course, assuming the NCQ implementation doesn't suck.... Cheers, Dave. -- Dave Chinner david@fromorbit.com