From: Jan Kara Subject: Re: [PATCH 1/1] Allow ext4 to run without a journal. Date: Thu, 18 Dec 2008 19:00:04 +0100 Message-ID: <20081218180004.GB6797@atrey.karlin.mff.cuni.cz> References: <1228953270.14314.15.camel@bobble.smo.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: Frank Mayhar Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:52180 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751513AbYLRSAF (ORCPT ); Thu, 18 Dec 2008 13:00:05 -0500 Content-Disposition: inline In-Reply-To: <1228953270.14314.15.camel@bobble.smo.corp.google.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: > A few weeks ago I posted a patch for discussion that allowed ext4 to run > without a journal. Since that time I've integrated the excellent > comments from Andreas and fixed several serious bugs. We're currently > running with this patch and generating some performance numbers against > both ext2 (with backported reservations code) and ext4 with and without > a journal. It just so happens that running without a journal is > slightly faster for most everything. > > We did > iozone -T -t 4 s 2g -r 256k -T -I -i0 -i1 -i2 > > which creates 4 threads, each of which create and do reads and writes on > a 2G file, with a buffer size of 256K, using O_DIRECT for all file opens > to bypass the page cache. Results: > > ext2 ext4, default ext4, no journal > initial writes 13.0 MB/s 15.4 MB/s 15.7 MB/s > rewrites 13.1 MB/s 15.6 MB/s 15.9 MB/s > reads 15.2 MB/s 16.9 MB/s 17.2 MB/s > re-reads 15.3 MB/s 16.9 MB/s 17.2 MB/s > random readers 5.6 MB/s 5.6 MB/s 5.7 MB/s > random writers 5.1 MB/s 5.3 MB/s 5.4 MB/s > > So it seems that, so far, this was a useful exercise. Interesting although I'm not that surprised because those tests seem to do a lot of data changes (which are never journaled in fact) and tiny amount of metadata changes. If you run some benchmark doing lots of directory operations, I guess the numbers would be considerably different. Maybe trying dbench (I know it's kind of stupid ;) or postmark will show the differences better. Honza -- Jan Kara SuSE CR Labs