Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752466AbYKMLLQ (ORCPT ); Thu, 13 Nov 2008 06:11:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751763AbYKMLLA (ORCPT ); Thu, 13 Nov 2008 06:11:00 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:34805 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750966AbYKMLK7 (ORCPT ); Thu, 13 Nov 2008 06:10:59 -0500 Date: Thu, 13 Nov 2008 12:10:40 +0100 From: Ingo Molnar To: Hidetoshi Seto Cc: linux-kernel@vger.kernel.org, Paul Menage , Peter Zijlstra , Mike Galbraith Subject: Re: [PATCH] accelerate newidle balancing in relax_domain Message-ID: <20081113111040.GA26461@elte.hu> References: <491C0A01.5040106@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <491C0A01.5040106@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2799 Lines: 68 * Hidetoshi Seto wrote: > Increasing the value of 'sched_relax_domain_level' in cpuset expands > the searching range of task balancing on some schedule events. As > the result it makes the task balancing in the range more aggressive, > so it will benefit some situation, such as where the latency is > required even it sacrifices cache hit rate etc. (for such situation, > it would be ideally best that cpus do not be idle until there are no > runnable task.) > > This patch aimed to accelerate the balancing in the relax_domain. > > The newidle balancing is kicked when tasks in a runqueue run out. It > finds and pulls runnable tasks from other busy cpus, checking load > imbalance between cpus. Considering above situation, using loads in > short term is preferred than that in long term because it makes > balancing more aggressive otherwise it becomes relatively > conservative. The referenced load is selected by the newidle_idx > parameter of scheduler domains, so this patch tunes the parameters > only when domains are in the relax_domain's range. There are no > effects if you don't use relax_domain. > > Following is a result of my short-lightweight-transaction test, showing > average of requester's latency (ms), 300 couple of threads running 30 sec > on 8cpu/Itanium: > > 1) v2.6.28-rc4 > Average 0.748783 Std Div 1.688022 Throughput 165313 > 2) v2.6.28-rc4 + relax_domain > Average 0.536867 Std Div 1.115383 Throughput 168492 > 3) v2.6.28-rc4 + relax_domain + patch > Average 0.385164 Std Div 0.801875 Throughput 170069 that improvement in metric looks good. > Signed-off-by: Hidetoshi Seto > --- > kernel/sched.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 57c933f..c970239 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -7366,6 +7366,8 @@ static void set_domain_attribute(struct sched_domain *sd, > } else { > /* turn on idle balance on this domain */ > sd->flags |= (SD_WAKE_IDLE_FAR|SD_BALANCE_NEWIDLE); > + /* make newidle balancing more aggressive */ > + sd->newidle_idx = 0; I agree with making it more sensitive to momentary load fluctuations. (as long as other metrics do not degrade). But this solutin basically overrides the newidle_idx tuning in topology.h. Is there a strong reason to do this tuning dynamically, or could we just decrease newidle_idx in the appropriate templates in the topology.h files? 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/