From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266324AbUBLKkX (ORCPT ); Thu, 12 Feb 2004 05:40:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266330AbUBLKkW (ORCPT ); Thu, 12 Feb 2004 05:40:22 -0500 Received: from columba.eur.3com.com ([161.71.171.238]:44799 "EHLO columba.eur.3com.com") by vger.kernel.org with ESMTP id S266324AbUBLKkS (ORCPT ); Thu, 12 Feb 2004 05:40:18 -0500 Message-ID: <402B580E.3000404@jburgess.uklinux.net> Date: Thu, 12 Feb 2004 10:40:14 +0000 From: Jon Burgess User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6) Gecko/20040113 X-Accept-Language: en-gb, en-us, en MIME-Version: 1.0 To: Rik van Riel CC: Jon Burgess , linux kernel Subject: Re: ext2/3 performance regression in 2.6 vs 2.4 for small interleaved writes References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Rik van Riel wrote: > Just for fun, could you also try measuring how long it takes > to read back the files in question ? > > Both individually and in parallel... > The original code did the read back as well, I stripped it out to make the code smaller to post. It was the read back performance that I was most interested in. I found that ext2/3 interleave all the blocks on the disk. With 2 stream the read performance is 50%, 4 streams give 25% etc. I have one really bad case where I record a TV stream at 500kByte/s + a radio one at 25kByte/s. These blocks are interleaved on the disk and the read performance of the radio stream is reduced by the data ratio, i.e. 1:20, so I get a miserable read performance of ~ 1MB/s. I found that ext2, ext3 and Reiserfs behave similarly. XFS and JFS appear to coalesce the data blocks during the write phase and can read the data back at near maximum performance. Jon