From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754676Ab1IPIOl (ORCPT ); Fri, 16 Sep 2011 04:14:41 -0400 Received: from smtp-out.google.com ([216.239.44.51]:59769 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754427Ab1IPIOh (ORCPT ); Fri, 16 Sep 2011 04:14:37 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=dkim-signature:message-id:date:from:user-agent: mime-version:newsgroups:to:cc:subject:references:in-reply-to: content-type:content-transfer-encoding:x-system-of-record; b=JyjxzaMAmFhLn/1sExqSWUTLsHGjWgsS0lpjG0BuGp3sGQjeDNuvNdQAsKPWa7n6Q 8CKYyquLrSaeA+m1MUkYQ== Message-ID: <4E730568.2030107@google.com> Date: Fri, 16 Sep 2011 01:14:32 -0700 From: Paul Turner User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:6.0.2) Gecko/20110902 Thunderbird/6.0.2 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel To: Peter Zijlstra CC: Srivatsa Vaddagiri , Kamalesh Babulal , Vladimir Davydov , "linux-kernel@vger.kernel.org" , Bharata B Rao , Dhaval Giani , Vaidyanathan Srinivasan , Ingo Molnar , Pavel Emelianov , Thomas Gleixner Subject: Re: CFS Bandwidth Control - Test results of cgroups tasks pinned vs unpinnede References: <20110615053716.GA390@linux.vnet.ibm.com> <20110907152009.GA3868@linux.vnet.ibm.com> <1315423342.11101.25.camel@twins> <20110908151433.GB6587@linux.vnet.ibm.com> <1315571462.26517.9.camel@twins> <20110912101722.GA28950@linux.vnet.ibm.com> <1315830943.26517.36.camel@twins> <20110913041545.GD11100@linux.vnet.ibm.com> <1315923579.5977.14.camel@twins> <20110913180146.GA12723@linux.vnet.ibm.com> <1315938226.4226.11.camel@twins> In-Reply-To: <1315938226.4226.11.camel@twins> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/13/11 11:23, Peter Zijlstra wrote: > On Tue, 2011-09-13 at 23:31 +0530, Srivatsa Vaddagiri wrote: >> * Peter Zijlstra [2011-09-13 16:19:39]: >> >>>> Booting with "nohz=off" also helps significantly. >>>> >>>> With nohz=on, average idle time (over 1 min) is 10.3% >>>> With nohz=off, average idle time (over 1 min) is 3.9% I think more compelling here is that it looks like nohz load-balance needs more love. >>> >>> So we should put the cpufreq/idle governor into the nohz/idle path, it >>> already tries to predict the idle duration in order to pick a C state, >>> that same prediction should be used to determine if stopping the tick is >>> worth it. >> >> Hmm ..I tried performance governor and found that it slightly increases >> idle time. >> >> With nohz=off&& ondemand governor, idle time = 4% >> With nohz=off&& performance governor on all cpus, idle time = 6% >> >> I can't see obvious reasons for that ..afaict bandwidth capping should >> be independent of frequency (i.e task gets capped by "used" time, >> irrespective of frequency at which it was "using" the cpu)? > > That's not what I said.. what I said is that the nohz code should also > use the idle time prognosis.. disabling the tick is a costly operation, > doing it only to have to undo it costs time, and will be accounted to > idle time, hence your improvement with nohz=off. > Enabling Venki's CONFIG_IRQ_TIME_ACCOUNTING=y would discount to provide a definitive answer here yes? - Paul