Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754147AbYH2NTH (ORCPT ); Fri, 29 Aug 2008 09:19:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754306AbYH2NSn (ORCPT ); Fri, 29 Aug 2008 09:18:43 -0400 Received: from E23SMTP03.au.ibm.com ([202.81.18.172]:35953 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753569AbYH2NSm (ORCPT ); Fri, 29 Aug 2008 09:18:42 -0400 Date: Fri, 29 Aug 2008 18:45:15 +0530 From: Vaidyanathan Srinivasan To: Linux Kernel Cc: Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi Subject: sched_mc_power_savings broken with CGROUPS+CPUSETS Message-ID: <20080829131514.GS4801@dirshya.in.ibm.com> Reply-To: svaidy@linux.vnet.ibm.com Mail-Followup-To: Linux Kernel , Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Balbir Singh , Suresh B Siddha , Venkatesh Pallipadi MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline 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: 1904 Lines: 53 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. Thanks, Vaidy Signed-off-by: Vaidyanathan Srinivasan Index: linux-2.6.27-rc5/kernel/sched.c =================================================================== --- linux-2.6.27-rc5.orig/kernel/sched.c 2008-08-29 17:48:56.000000000 +0000 +++ linux-2.6.27-rc5/kernel/sched.c 2008-08-29 18:16:09.000000000 +0000 @@ -3375,6 +3375,8 @@ out_balanced: #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) + BUG_ON(sched_mc_power_savings && sd->level == SD_LV_CPU && + !(sd->flags & SD_POWERSAVINGS_BALANCE)); if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE)) goto ret; -- 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/