Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 21 Feb 2003 00:17:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 21 Feb 2003 00:16:49 -0500 Received: from packet.digeo.com ([12.110.80.53]:39611 "EHLO packet.digeo.com") by vger.kernel.org with ESMTP id ; Fri, 21 Feb 2003 00:16:19 -0500 Date: Thu, 20 Feb 2003 21:27:58 -0800 From: Andrew Morton To: linux-kernel@vger.kernel.org Subject: iosched: impact of streaming read on read-many-files Message-Id: <20030220212758.5064927f.akpm@digeo.com> In-Reply-To: <20030220212304.4712fee9.akpm@digeo.com> References: <20030220212304.4712fee9.akpm@digeo.com> X-Mailer: Sylpheed version 0.8.9 (GTK+ 1.2.10; i586-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 21 Feb 2003 05:26:20.0063 (UTC) FILETIME=[C3DD02F0:01C2D969] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1899 Lines: 54 Here we look at what affect a large streaming read has upon an operation which reads many small files from the same disk. A single streaming read was set up with: while true do cat 512M-file > /dev/null done and we measure how long it takes to read all the files from a 2.4.19 kernel tree off the same disk with time (find kernel-tree -type f | xargs cat > /dev/null) 2.4.21-pre4: 31 minutes 30 seconds 2.5.61+hacks: 3 minutes 39 seconds 2.5.61+CFQ: 5 minutes 7 seconds (*) 2.5.61+AS: 17 seconds * CFQ performed very strangely here. Tremendous amount of seeking and a big drop in aggregate bandwidth. See the vmstat 1 output from when the kernel tree read started up: r b swpd free buff cache si so bi bo in cs us sy id wa 0 1 1240 125260 1176 109488 0 0 40744 0 1672 725 0 3 49 47 0 1 1240 85892 1220 148788 0 0 39344 0 1651 693 0 3 49 48 0 1 1240 45124 1260 189492 0 0 40744 0 1663 683 0 3 49 47 1 1 1240 4544 1300 230068 0 0 40616 0 1661 837 0 4 49 47 0 2 1348 3468 944 231696 0 108 40488 148 1671 800 0 4 4 91 0 2 1348 2180 936 232920 0 0 40612 64 1668 789 0 4 0 96 0 3 1348 4220 996 230648 0 0 11348 0 1256 352 0 2 0 98 0 3 1348 4052 1064 230472 0 0 9012 0 1207 305 0 1 0 98 0 4 1348 3596 1148 230580 0 0 6756 0 1171 247 0 1 0 99 0 4 1348 4044 1148 229888 0 0 6344 0 1165 237 0 1 0 99 1 3 1348 3708 1160 230212 0 0 7800 0 1187 255 0 1 21 78 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/