From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p5M0Jg6k039169 for ; Tue, 21 Jun 2011 19:19:42 -0500 Received: from ipmail06.adl6.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 6617C22D3E for ; Tue, 21 Jun 2011 17:19:40 -0700 (PDT) Received: from ipmail06.adl6.internode.on.net (ipmail06.adl6.internode.on.net [150.101.137.145]) by cuda.sgi.com with ESMTP id tN0fO0jdCW0ftGRy for ; Tue, 21 Jun 2011 17:19:40 -0700 (PDT) Date: Wed, 22 Jun 2011 10:19:37 +1000 From: Dave Chinner Subject: Re: [PATCH] xfs: improve sync behaviour in face of aggressive dirtying Message-ID: <20110622001937.GR32466@dastard> References: <20110617131401.GC2141@infradead.org> <20110620081802.GA27111@infradead.org> <20110621003343.GJ32466@dastard> <201106210921.48657@zmi.at> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <201106210921.48657@zmi.at> 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: Michael Monnerie Cc: Christoph Hellwig , Wu Fengguang , xfs@oss.sgi.com On Tue, Jun 21, 2011 at 09:21:46AM +0200, Michael Monnerie wrote: > On Dienstag, 21. Juni 2011 Dave Chinner wrote: > > > The minor one is that we always flush all work items and not just > > > those on the filesystem to be flushed. This might become an issue > > > for lager systems, or when we apply a similar scheme to fsync, > > > which has the same underlying issue. > > > > For sync, I don't think it matters if we flush a few extra IO > > completions on a busy system. > > Couldn't that be bad on a system with mixed fast/slow storage (say 15k > SAS and 7.2k SATA), where on the busy fast SAS lots of syncs occur and > lead to extra I/O on the SATA disks? Especially if there are 16 SAS > disks in an array with RAID-0 against 4 SATA disks in RAID-6, to say the > worst. If the SATAs are already heavy used (say >=50%), those extra > writes could bring them to their knees. We are not talking about issuing extra writes to disk, so you don't have to worry about this. What we are talking about is how to efficiently flush the XFS IO completion queues for writes that the hardware has already completed. That's almost always just CPU overhead and doesn't involve more IO.... ;) Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs