Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755932AbXHVH7j (ORCPT ); Wed, 22 Aug 2007 03:59:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755759AbXHVH7b (ORCPT ); Wed, 22 Aug 2007 03:59:31 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:56714 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755552AbXHVH7a (ORCPT ); Wed, 22 Aug 2007 03:59:30 -0400 Date: Wed, 22 Aug 2007 09:59:13 +0200 From: Ingo Molnar To: Christian Borntraeger Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Martin Schwidefsky , Jan Glauber , heiko.carstens@de.ibm.com, Paul Mackerras Subject: Re: [accounting regression since rc1] scheduler updates Message-ID: <20070822075912.GA7411@elte.hu> References: <20070812163225.GA11996@elte.hu> <200708211017.02998.borntraeger@de.ibm.com> <20070821112529.GB648@elte.hu> <200708220950.35044.borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200708220950.35044.borntraeger@de.ibm.com> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: 1.0 X-ELTE-SpamLevel: s X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=1.0 required=5.9 tests=BAYES_50 autolearn=no SpamAssassin version=3.0.3 1.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.4973] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1768 Lines: 41 * Christian Borntraeger wrote: > Am Dienstag, 21. August 2007 schrieben Sie: > > could you try the patch below, does it work any better? > > I looked again at the scheduler code and things are getting better > when I run the patch below on top of your patch and with our > sched_clock prototype. I guess there is a reason why you want > rq->clock advanced by at least one tick? yeah - on PCs if for whatever reason the TSC misbehaves (and that's quite frequent) then this code sets a minimum boundary for behavior. If sched_clock() is totally random or does not advance at all or goes backwards all the time then rq_clock() still functions and falls back to jiffies-granularity behavior in essence. > We discussed calling scheduler_tick with virtual time as well. > Would it have the same result? > What would be the impact on latency? if you call scheduler_tick() with virtual time then the "safety" measures in rq_clock() do not kick in and sched_clock() behaves correctly as far as the scheduler is concerned. (if everything is in virtual time then the scheduler has no way to observe/notice that in reality this is a virtual machine.) > After looking at the current s390 timer code, it seems that this kind of > change is not trivial enough to be rc3+ ready. > I personally think, that for 2.6.23 we should use the patch against > fs/proc/array.c and everything else for 2.6.24? yes, that has the least impact for .23 - i have added your array.c patch to my queue. 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/