From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o8C10kDE234695 for ; Sat, 11 Sep 2010 20:00:46 -0500 Received: from mail.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id C5DE317DABCE for ; Sat, 11 Sep 2010 18:01:31 -0700 (PDT) Received: from mail.internode.on.net (bld-mail12.adl6.internode.on.net [150.101.137.97]) by cuda.sgi.com with ESMTP id m8YY4nu6hfysshJo for ; Sat, 11 Sep 2010 18:01:31 -0700 (PDT) Date: Sun, 12 Sep 2010 11:01:27 +1000 From: Dave Chinner Subject: Re: XFS defragmentation issue Message-ID: <20100912010127.GA411@dastard> References: <4C8A4395.5070702@kickstone.com> <4C8B27E4.2050102@kickstone.com> <20100911082330.GG705@dastard> <4C8BDAC8.8010203@hardwarefreak.com> <20100911195702.GB25185@teal.hq.k1024.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100911195702.GB25185@teal.hq.k1024.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Stan Hoeppner , xfs@oss.sgi.com On Sat, Sep 11, 2010 at 09:57:02PM +0200, Iustin Pop wrote: > On Sat, Sep 11, 2010 at 02:38:48PM -0500, Stan Hoeppner wrote: > > Dave Chinner put forth on 9/11/2010 3:23 AM: > > > On Sat, Sep 11, 2010 at 07:55:32AM +0100, John Lister wrote: > > >> Stan Hoeppner wrote on 9/10/2010 14:00 > > >>>> On 10/09/2010 15:41, John Lister wrote: > > >>> Try unmounting and remounting the filesystem, and see if the various > > >>> tools all report the same thing afterwards. This solved the exact same > > >>> problem for me very recently, though I'm on kernel 2.6.34.1 and xfsprogs > > >>> 2.9.8. > > >> > > >> Cheers, that got rid of most of it, there is still a slight > > >> discrepency (50 extra fragments) which I can live with. > > > > > > xfs_db used buffered IO on the block device, which is not coherent > > > with the filesystem. If you are using it on an active filesystem, > > > then running "echo 1 > /proc/sys/vm/drop_caches" before you run > > > xfs_db should make it read from disk at least once.... > > I wonder if xfs_db shouldn't use by default direct I/O, or at least take > a flag to allow it to do direct I/O only against the blocks it needs. > Dropping the entire caches on a big box is not nice :) True - I need to look at whether posix_fadvise(POSIX_FADV_DONTNEED) will clear the bdev pages, and if so that is the easiest solution. Rewriting xfs_db to use direct IO is a pretty major undertaking... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs