From: Theodore Tso Subject: Re: [ext4] Documentation patch Date: Sat, 6 Dec 2008 17:25:35 -0500 Message-ID: <20081206222534.GJ1323@mit.edu> References: <8763m3u9kv.fsf@basilikum.skogtun.org> <20081201165700.GA26680@infradead.org> <493425DC.1010008@redhat.com> <20081201205828.GA20069@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Eric Sandeen , Christoph Hellwig , Harald Arnesen , linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Return-path: Received: from www.church-of-our-saviour.org ([69.25.196.31]:55362 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752850AbYLFWZv (ORCPT ); Sat, 6 Dec 2008 17:25:51 -0500 Content-Disposition: inline In-Reply-To: <20081201205828.GA20069@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: This is what I have added to the ext4 patch queue. - Ted Update Documentation/filesystems/ext4.txt Fix paragraph with recommendations on how to tune ext4 for benchmarks. Signed-off-by: "Theodore Ts'o" diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 845e691..19bb93f 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -58,13 +58,18 @@ Note: More extensive information for getting started with ext4 can be # mount -t ext4 /dev/hda1 /wherever - - When comparing performance with other filesystems, remember that - ext3/4 by default offers higher data integrity guarantees than most. - So when comparing with a metadata-only journalling filesystem, such - as ext3, use `mount -o data=writeback'. And you might as well use - `mount -o nobh' too along with it. Making the journal larger than - the mke2fs default often helps performance with metadata-intensive - workloads. + - When comparing performance with other filesystems, it's always + important to try multiple workloads; very often a subtle change in a + workload parameter can completely change the ranking of which + filesystems do well compared to others. When comparing versus ext3, + note that ext4 enables write barriers by default, while ext3 does + not enable write barriers by default. So it is useful to use + explicitly specify whether barriers are enabled or not when via the + '-o barriers=[0|1]' mount option. When tuning ext3 for best + benchmark numbers, it is often worthwhile to try changing the data + journaling mode; '-o data=writeback,nobh' can be faster for some + workloads. A large journal can also be helpful for + metadata-intensive workloads. 2. Features ===========