From: Theodore Tso Subject: Re: [PATCH] ext4: Fix small file fragmentation Date: Fri, 15 Aug 2008 09:38:03 -0400 Message-ID: <20080815133803.GL13048@mit.edu> References: <1218735880-10915-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20080814231816.GA13048@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: cmm@us.ibm.com, sandeen@redhat.com, linux-ext4@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from www.church-of-our-saviour.org ([69.25.196.31]:38616 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753452AbYHONiT (ORCPT ); Fri, 15 Aug 2008 09:38:19 -0400 Content-Disposition: inline In-Reply-To: <20080814231816.GA13048@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Here's an interesting data point. Using Chris Mason's compilebench: http://oss.oracle.com/~mason/compilebench If I use: ./compilebench -D /mnt -i 2 -r 0 on a 4GB machine such that I have plenty of memory (and nothing gets forced disk due to memory pressure), I don't see hardly any of the small file fragmentation problem (0.8% of the inodes in use on the filesystem. This is with your patch applied. However, if I use: ./compilebench -D /mnt -i 10 -r 0 so that data blocks are getting pushed out due to memory pressure, then I see plenty of non-contiugous inodes (8.1% of the inodes in use on the filesystem). So with your patch applied, it seems that we still have a problem related to delayed allocation and how the VM system is doing its page cleaning. - Ted