Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755205AbYH3T7S (ORCPT ); Sat, 30 Aug 2008 15:59:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752831AbYH3T7H (ORCPT ); Sat, 30 Aug 2008 15:59:07 -0400 Received: from E23SMTP06.au.ibm.com ([202.81.18.175]:53890 "EHLO e23smtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbYH3T7E (ORCPT ); Sat, 30 Aug 2008 15:59:04 -0400 Date: Sun, 31 Aug 2008 01:32:41 +0530 From: Vaidyanathan Srinivasan To: Max Krasnyansky Cc: Linux Kernel , Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi Subject: Re: sched_mc_power_savings broken with CGROUPS+CPUSETS Message-ID: <20080830200241.GA6124@dirshya.in.ibm.com> Reply-To: svaidy@linux.vnet.ibm.com Mail-Followup-To: Max Krasnyansky , Linux Kernel , Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi References: <20080829131514.GS4801@dirshya.in.ibm.com> <48B8593E.7050205@qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <48B8593E.7050205@qualcomm.com> 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: 2233 Lines: 57 * Max Krasnyansky [2008-08-29 13:17:02]: > 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. > > That's my fault. I redid domain rebuild/hotplug handling awhile ago and missed > the fact that partition_sched_domains() is trying to avoid unnecessary domain > rebuilds. Primary issue at the time was circular locking issues and the the > testing that I was doing then was exercising a bunch of different scenarios > (ie cpu up/down, cpuset create/destroy, mcpowersave on/off) and I did not > notice that mcpowersave did not actually trigger domain rebuilds. > > Anyway, I sent you guys a patch that should fix this issue. > Please confirm. Hi Max, Thank you very much for identifying the source of the problem. I will test your patch and report. My BUG_ON() may still fail during the window of change. I will watch out for that. --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/