From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754424AbZHYIBG (ORCPT ); Tue, 25 Aug 2009 04:01:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753693AbZHYIBD (ORCPT ); Tue, 25 Aug 2009 04:01:03 -0400 Received: from sg2ehsobe002.messaging.microsoft.com ([207.46.51.76]:27720 "EHLO SG2EHSOBE002.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751050AbZHYIBB convert rfc822-to-8bit (ORCPT ); Tue, 25 Aug 2009 04:01:01 -0400 X-SpamScore: -8 X-BigFish: VPS-8(z1857r34a4j8deiz1432R98dN936eM4015La594izz1202hzzz32i203h6bh43j61h) X-Spam-TCS-SCL: 0:0 X-WSS-ID: 0KOXA9F-01-1QT-02 X-M-MSG: Date: Tue, 25 Aug 2009 10:00:20 +0200 From: Andreas Herrmann To: Vaidyanathan Srinivasan CC: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH 10/15] sched: Check for sched_mn_power_savings when doing load balancing Message-ID: <20090825080020.GD20811@alberich.amd.com> References: <20090820131243.GO29327@alberich.amd.com> <20090820134104.GY29327@alberich.amd.com> <1251126220.7538.273.camel@twins> <20090824154013.GM6474@dirshya.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline In-Reply-To: <20090824154013.GM6474@dirshya.in.ibm.com> User-Agent: Mutt/1.5.16 (2007-06-09) X-OriginalArrivalTime: 25 Aug 2009 08:00:20.0598 (UTC) FILETIME=[178E8160:01CA255A] Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 24, 2009 at 09:10:13PM +0530, Vaidyanathan Srinivasan wrote: > * Peter Zijlstra [2009-08-24 17:03:40]: > > > On Thu, 2009-08-20 at 15:41 +0200, Andreas Herrmann wrote: > > > The patch adds support for POWERSAVINGS_BALANCE_BASIC for MN domain > > > level. Currently POWERSAVINGS_BALANCE_WAKEUP is not used for MN domain. > > > > > > (I have to admit that so far I don't have the correct understanding > > > what's the benefit of POWERSAVINGS_BALANCE_WAKEUP (when an deticated > > > wakeup CPU is used) in contrast to POWERSAVINGS_BALANCE_BASIC. I also > > > have not found an example that would demonstrate the difference > > > between those two powersaving levels.) > > > > blame svaidy for not writing enough comments ;-) > > I am here to explain ;) > > > iirc it moves tasks to sched_mv_preferred_wakeup_cpu instead of waking > > an idle cpu, this leaves idle cpus idle longer at the cost of creating > > overload on other cpus. > > Yes, as Peter said, the POWERSAVINGS_BALANCE_WAKEUP biases task > wakeups to sched_mc_preferred_wakeup_cpu which has been nominated from > previous load balance loops. > > Task wakeup biasing of sched_mc=2 works for most workloads like > kernbench and other sleeping tasks that come in and out of runqueue. > The default sched_mc=1 will work only for jobs running much longer > than the loadbalance interval or almost 100% CPU intensive job where Ok, one of my tests was using 100% CPU intensive jobs and for those the sched_mc=1 or sched_mn=1 level was sufficient to show the effect of loadbalancing. > the load balancer can take time to identify the load pattern and > initiate a task migrate. > The wakeup biasing (sched_mc=2) will help move bursty jobs faster and > statistically pack them in single package and save power. That means that wakeup biasing will also make sense for the MN domain. Thanks, Andreas -- Operating | Advanced Micro Devices GmbH System | Karl-Hammerschmidt-Str. 34, 85609 Dornach b. München, Germany Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München (OSRC) | Registergericht München, HRB Nr. 43632