Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755373AbXFNUnU (ORCPT ); Thu, 14 Jun 2007 16:43:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754082AbXFNUnC (ORCPT ); Thu, 14 Jun 2007 16:43:02 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:47588 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753839AbXFNUnA (ORCPT ); Thu, 14 Jun 2007 16:43:00 -0400 Date: Thu, 14 Jun 2007 22:42:53 +0200 From: Ingo Molnar To: Vassili Karpov Cc: linux-kernel@vger.kernel.org Subject: Re: [patch] sched: accurate user accounting Message-ID: <20070614204253.GA14076@elte.hu> References: <200703251159.03616.kernel@kolivas.org> <200703260901.54943.kernel@kolivas.org> <200703260957.34798.kernel@kolivas.org> <20070328113743.GA5615@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1921 Lines: 44 * Vassili Karpov wrote: > Hello Ingo and others, > > After reading http://lwn.net/Articles/236485/ and noticing few > refernces to accounting i decided to give CFS a try. With > sched-cfs-v2.6.21.4-16 i get pretty weird results, it seems like > scheduler is dead set on trying to move the processes to different > CPUs/cores all the time. And with hog (manually tweaking the amount > iterations) i get fairly strange resuls, first of all the process is > split between two cores, secondly while integral load provided by the > kernel looks correct, it's off by good 20 percent on each idividial > core. > > (http://www.boblycat.org/~malc/apc/hog-cfs-v16.png) > > Thought this information might be of some interest. hm - what does 'hog' do, can i download hog.c from somewhere? the alternating balancing might be due to an uneven number of tasks perhaps? If you have 3 tasks on 2 cores then there's no other solution to achieve even performance of each task but to rotate them amongst the cores. > P.S. How come the /proc/stat information is much closer to reality > now? Something like what Con Kolivas suggested was added to > sched.c? well, precise/finegrained accounting patches have been available for years, the thing with CFS is that there we get them 'for free', because CFS needs those metrics for its own logic. That's why this information is much closer to reality now. But note: right now what is affected by the changes in the CFS patches is /proc/PID/stat (i.e. the per-task information that 'top' and 'ps' displays, _not_ /proc/stat) - but more accurate /proc/stat could certainly come later on too. Ingo - 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/