From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261466AbUBUBUi (ORCPT ); Fri, 20 Feb 2004 20:20:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261468AbUBUBUi (ORCPT ); Fri, 20 Feb 2004 20:20:38 -0500 Received: from fw.osdl.org ([65.172.181.6]:37046 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261466AbUBUBUh (ORCPT ); Fri, 20 Feb 2004 20:20:37 -0500 Date: Fri, 20 Feb 2004 17:22:29 -0800 From: Andrew Morton To: "John Chatelle" Cc: linux-kernel@vger.kernel.org Subject: Re: High read Latency test (Anticipatory I/O scheduler) Message-Id: <20040220172229.736cb249.akpm@osdl.org> In-Reply-To: <20040220202023.M9162@medent.com> References: <20040220202023.M9162@medent.com> X-Mailer: Sylpheed version 0.9.7 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "John Chatelle" wrote: > > #StreamingRead.sh --simple 4 line shell script: > while true > do > cat ../data/oneGBfile >/dev/null > done > > #WHR.sh -- simple 2 (or 3) line shell script. > StreamingRead.sh & > time find /usr/src/linux-2.4.20-18.7 -type f -exec cat \ > '{}' ';' > /dev/null Note that the latter test runs `cat' once per file: over ten thousand times. You should also test: time (find /usr/src/linux-2.4.20-18.7 -type f | xargs cat > /dev/null ) which will run `cat' only some tens of times. For the anticipatory scheduler, this makes a significant difference - the run-cat-once-per-file problem has specific fixes and perhaps they're not working right at present. And yes, please describe your disk system, tell us the tag depth (if it is scsi) and try Nick's patch, thanks.