From: Theodore Tso Subject: Re: Performance of ext4 Date: Thu, 19 Jun 2008 07:09:47 -0400 Message-ID: <20080619110947.GB11516@mit.edu> References: <20080612131928.GB18229@mit.edu> <20080612180605.GD22481@skywalker> <20080616175408.GF3279@atrey.karlin.mff.cuni.cz> <20080616181353.GA20686@skywalker> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Aneesh Kumar K.V" , Jan Kara , Solofo.Ramangalahy@bull.net, Nick Dokos , linux-ext4@vger.kernel.org, linux-kernel To: Holger Kiehl Return-path: Received: from www.church-of-our-saviour.org ([69.25.196.31]:57567 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756034AbYFSLLO (ORCPT ); Thu, 19 Jun 2008 07:11:14 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Jun 18, 2008 at 05:58:00AM +0000, Holger Kiehl wrote: > For afdbench: 5336.41 files per second 15.63 MiB/s > > So it seems that for afdbench the ext4-patch-queue is a slowdown. Can you remind me where afdbench can be downloaded? And if I remember correctly, it creates and deletes large numbers of small files, correct? It would be interesting to see which new feature introduced by the ext4 patch queue --- probably dellayed allocation or mballoc --- is responsible for the slowdown. One or the other (or both) can be disabled by mounting the filesystem (using a kernel with the ext4 patch queue) with the mount options -O nomballoc or -O nodelalloc. If it turns out that nomballoc restores the speed for afdbench, for example, then it will tell us where we need to look more closely. Ideally we would not want to have one mount option needed to optimize filesystem operations for large amoutns of modifications to small files, and another mode of operation when mostly writing to large files. So if you could do a round of tests using the ext4 patch queue kernel, with -O nomballoc and -O nodelalloc (and if both seem to improve things, try "-O nomballoc,nodelalloc" and see if you get back to the pre-ext4 patch queue speed), it would be very much appreciated. Thanks, regards, - Ted