From: Christoph Hellwig Subject: Re: ext4 writepages is making tiny bios? Date: Thu, 3 Sep 2009 12:42:09 -0400 Message-ID: <20090903164209.GA28384@infradead.org> References: <20090901184450.GB7885@think> <20090901205744.GE6996@mit.edu> <20090901212740.GA9930@infradead.org> <20090903055201.GA7146@discord.disaster> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Theodore Tso , Chris Mason , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com To: Dave Chinner Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:49692 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932081AbZICQmM (ORCPT ); Thu, 3 Sep 2009 12:42:12 -0400 Content-Disposition: inline In-Reply-To: <20090903055201.GA7146@discord.disaster> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Sep 03, 2009 at 03:52:01PM +1000, Dave Chinner wrote: > > XFS did the mistake of trusting the VM, while everyone more or less > > overrode it. Removing all those checks and writing out much larger > > data fixes it with a relatively small patch: > > > > http://verein.lst.de/~hch/xfs/xfs-writeback-scaling > > 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?