From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756953AbYCNMOh (ORCPT ); Fri, 14 Mar 2008 08:14:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751078AbYCNMO3 (ORCPT ); Fri, 14 Mar 2008 08:14:29 -0400 Received: from g4t0015.houston.hp.com ([15.201.24.18]:26390 "EHLO g4t0015.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752485AbYCNMO2 (ORCPT ); Fri, 14 Mar 2008 08:14:28 -0400 Message-ID: <47DA6C1E.8010000@hp.com> Date: Fri, 14 Mar 2008 08:14:22 -0400 From: "Alan D. Brunelle" User-Agent: Thunderbird 2.0.0.12 (X11/20080227) MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Cc: Jens Axboe , npiggin@suse.de, dgc@sgi.com Subject: IO CPU affinity test results Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Good morning Jens - I had two machines running the latest patches hang last night: o 2-way AMD64 - I inadvertently left the patched kernel running, and I was moving a ton of data (100+GB) back up over the net to this node. It hard hung (believe it or not) about 99% of the way through. Hard hang, wouldn't respond to anything. o 4-way IA64 - I was performing a simple test: [mkfs / mount / untar linux sources / make allnoconfig / make -j 5 / umount] repeatedly switching rq_affinity to 0/1 between each run. After 22 passes it had a hard hang with rq_affinity set to 1. Of course, there is no way of knowing if either hang had anything to do with the patches, but it seems a bit ominous as RQ=1 was set in both cases. This same test worked fine for 30 passes on a 2-way AMD64 box, with the following results: Part RQ MIN AVG MAX Dev ----- -- ------ ------ ------ ------ mkfs 0 41.656 41.862 42.086 0.141 mkfs 1 41.618 41.909 42.270 0.192 untar 0 18.055 19.611 20.906 0.720 untar 1 18.523 19.905 21.988 0.738 make 0 50.480 50.991 51.752 0.340 make 1 49.819 50.442 51.000 0.292 comb 0 110.433 112.464 114.176 0.932 comb 1 110.694 112.256 114.683 0.948 psys 0 10.28% 10.91% 11.29% 0.243 psys 1 10.21% 11.05% 11.80% 0.350 All results are in seconds (as measured by Python's time.time()), except for the psys - which was the average of mpstat's %sys column over the life of the whole run. The mkfs part consisted of [mkfs -t ext2 ; sync ; sync], untar [mount; untar linux sources; umount; sync; sync], make [mount; make allnoconfig; make -j 3; umount; sync; sync], and comb is the combined times of the mkfs, untar and make parts. So, in a nutshell, we saw slightly better overall performance, but not conclusively, and we saw slightly elevated %system time to accomplish the task. On the 4-way, results were much worse: the final data shown before the system hung showed the rq=1 passes taking significantly longer, albeit at lower %system. I'm going to try the runs again, but I have a feeling that the latest "clean" patch based upon Nick's single call mechanism is a step backwards. Alan