From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: ext4 writepages is making tiny bios? Date: Fri, 4 Sep 2009 09:20:13 +0200 Message-ID: <20090904072013.GR18599@kernel.dk> References: <20090901184450.GB7885@think> <20090901205744.GE6996@mit.edu> <20090901212740.GA9930@infradead.org> <20090903055201.GA7146@discord.disaster> <20090903164209.GA28384@infradead.org> <20090904001545.GA30759@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Dave Chinner , Chris Mason , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com To: Theodore Tso Return-path: Received: from brick.kernel.dk ([93.163.65.50]:39692 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756594AbZIDHUL (ORCPT ); Fri, 4 Sep 2009 03:20:11 -0400 Content-Disposition: inline In-Reply-To: <20090904001545.GA30759@mit.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Sep 03 2009, Theodore Tso wrote: > On Thu, Sep 03, 2009 at 12:42:09PM -0400, Christoph Hellwig wrote: > > > Careful: > > > > > > - tloff = min(tlast, startpage->index + 64); > > > + tloff = min(tlast, startpage->index + 8192); > > > > > > That will cause 64k page machines to try to write back 512MB at a > > > time. This will re-introduce similar to the behaviour in sles9 where > > > writeback would only terminate at the end of an extent (because the > > > mapping end wasn't capped like above). > > > > Pretty good point, any applies to all the different things we discussed > > recently. Ted, should be maybe introduce a max_writeback_mb instead of > > the max_writeback_pages in the VM, too? > > Good point. > > Jens, maybe we should replace my patch with this one, which makes the > tunable in terms of megabytes instead of pages? That is probably a better metric than 'pages', lets update it. -- Jens Axboe