From: Andreas Dilger Subject: Re: buffered writeback torture program Date: Thu, 21 Apr 2011 11:59:37 -0600 Message-ID: <93CB867E-B908-4B38-A146-A9DC958ACF64@dilger.ca> References: <1303322378-sup-1722@think> <20110421083258.GA26784@infradead.org> <1303407205-sup-6141@think> <20110421174120.GA7267@infradead.org> Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: Chris Mason , linux-fsdevel , linux-ext4 , xfs , jack , axboe , dchinner To: Christoph Hellwig Return-path: Received: from idcmail-mo1so.shaw.ca ([24.71.223.10]:25112 "EHLO idcmail-mo1so.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752391Ab1DUR7j convert rfc822-to-8bit (ORCPT ); Thu, 21 Apr 2011 13:59:39 -0400 In-Reply-To: <20110421174120.GA7267@infradead.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 2011-04-21, at 11:41 AM, Christoph Hellwig wrote: > On Thu, Apr 21, 2011 at 01:34:44PM -0400, Chris Mason wrote: >> Sorry, this doesn't do it. I think that given what a strange special >> case this is, we're best off waiting for the IO-less throttling, and >> maybe changing the code in xfs/ext4 to be a little more seek aware. Or >> maybe not, it has to get written eventually either way. > > I'm not sure what you mean with seek aware. XFS only clusters > additional pages that are in the same extent, and in fact only does > so for asynchrononous writeback. Not sure how this should be more > seek aware. But doesn't XFS have potentially very large extents, especially in the case of files that were fallocate()'d or linearly written? If there is a single 8GB extent, and then random writes within that extent (seems very database like) grouping the all of the writes in the extent doesn't seem so great. Cheers, Andreas