From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753438AbZHKMHa (ORCPT ); Tue, 11 Aug 2009 08:07:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753413AbZHKMH0 (ORCPT ); Tue, 11 Aug 2009 08:07:26 -0400 Received: from mailhost11.gawab.com ([66.220.20.11]:47883 "HELO info12.gawab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753366AbZHKMHW (ORCPT ); Tue, 11 Aug 2009 08:07:22 -0400 X-Trusted: Whitelisted From: Al Boldi To: Jan Kara Subject: Re: [PATCH, RFC] ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED Date: Tue, 11 Aug 2009 14:41:01 +0300 User-Agent: KMail/1.5 Cc: "Theodore Ts'o" , Jan Kara , Linux Kernel Developers List , linux-ext4@vger.kernel.org References: <1249934623-15939-1-git-send-email-tytso@mit.edu> <200908110649.20277.a1426z@gawab.com> <20090811093316.GA23898@duck.suse.cz> In-Reply-To: <20090811093316.GA23898@duck.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200908111441.01832.a1426z@gawab.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jan Kara wrote: > On Tue 11-08-09 06:49:20, Al Boldi wrote: > > Theodore Ts'o wrote: > > > + "data=ordered" mode can also result in major performance > > > + problems, including seconds-long delays before an fsync() > > > + call returns. For details, see: > > > + > > > + http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs > > > > Why isn't the fsync problem fixable? > > Because it's quite deep in the design of JBD: All the modifications done > to a filesystem go to one transactions. When the transaction grows big > enough or old enough, we commit the transaction, which means we write all > the metadata to the journal and all the ordered data to their final > location on disk. If you do fsync(), you have to wait for a transaction > commit with your data to finish, so that you are guaranteed a consistent > state of metadata is on disk. But when there is heavy background writing, > it means there's a lot of data you have to write out and wait for... It's > not easy to work around this - naively, you might want to separate out just > the writes you care about for fsync() but that's not easily possible > because bitmaps and group descriptors are modified by other writes as well. Ok, I remember now, that was the konqueror deadlocks problem. I think making the fsync soft in that case would yield a better result than turning ordered-mode off completely. BTW: did you get around fixing the ordered-mode redundant write out problem? Thanks! -- Al