Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758634AbYH2OIk (ORCPT ); Fri, 29 Aug 2008 10:08:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758143AbYH2OI0 (ORCPT ); Fri, 29 Aug 2008 10:08:26 -0400 Received: from ausmtp04.au.ibm.com ([202.81.18.152]:51764 "EHLO ausmtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757881AbYH2OIZ (ORCPT ); Fri, 29 Aug 2008 10:08:25 -0400 Date: Fri, 29 Aug 2008 19:35:44 +0530 From: Vaidyanathan Srinivasan To: Peter Zijlstra Cc: Linux Kernel , Ingo Molnar , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi , Gregory Haskins Subject: Re: sched_mc_power_savings broken with CGROUPS+CPUSETS Message-ID: <20080829140544.GT4801@dirshya.in.ibm.com> Reply-To: svaidy@linux.vnet.ibm.com Mail-Followup-To: Peter Zijlstra , Linux Kernel , Ingo Molnar , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi , Gregory Haskins References: <20080829131514.GS4801@dirshya.in.ibm.com> <1220016237.17355.48.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1220016237.17355.48.camel@twins> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2127 Lines: 54 * Peter Zijlstra [2008-08-29 15:23:57]: > On Fri, 2008-08-29 at 18:45 +0530, Vaidyanathan Srinivasan wrote: > > Hi, > > > > sched_mc_power_savings seems to be broken with CGROUPS+CPUSETS. > > When CONFIG_CPUSETS=y the attached BUG_ON() is being hit. > > > > I added a BUG_ON to check if SD_POWERSAVINGS_BALANCE is set at > > SD_LV_CPU whenever sched_mc_power_savings is set. > > > > This BUG is hit when config CONFIG_CPUSETS (depends on CONFIG_CGROUPS) > > is just compiled in while this is never hit when they are compiled > > out. The fact that SD_POWERSAVINGS_BALANCE being cleared even when > > sched_mc_power_savings = 1 completely breaks the > > sched_mc_power_savings heuristics. > > > > To recreate the problem, > > Have sched_mc power savings enabled CONFIG_SCHED_MC=y > > Add this BUG_ON() > > > > echo 1 > /sys/devices/system/cpu/sched_mc_power_savings > > > > Try these these on a multi core x86 box. > > > > sched_mc_power_savings seems to be broken from 2.6.26-rc1, but > > I do not have a confirmation that the root cause is same in all > > successive versions. sched_mc_power_savings works perfect in > > 2.6.25. > > > > Please help me root cause the issue. Please point me to changes that > > may potential cause this bug. > > I'm still greatly mistified by all that power savings code. > > Its hard to read and utterly hard to comprehend - I've been about to rip > the whole stuff out on several occasions. But so far tried to carefully > thread around it maintaining its operation even though not fully > understood. > > Someone with clue - preferably the authors of the code in question - > should enlighten us with a patch that adds some comments as to the > intent of said lines of code. I will try to add my notes around it. I have been playing around with sched_mc to make it work for different workloads. --Vaidy -- 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/