Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751633AbZGXEb6 (ORCPT ); Fri, 24 Jul 2009 00:31:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751076AbZGXEb5 (ORCPT ); Fri, 24 Jul 2009 00:31:57 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:39327 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbZGXEb5 (ORCPT ); Fri, 24 Jul 2009 00:31:57 -0400 Date: Fri, 24 Jul 2009 10:00:01 +0530 From: Bharata B Rao To: Ken Chen Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Dhaval Giani , Srivatsa Vaddagiri , Balbir Singh Subject: Re: CFS group scheduler fairness broken starting from 2.6.29-rc1 Message-ID: <20090724043001.GC5304@in.ibm.com> Reply-To: bharata@linux.vnet.ibm.com References: <20090723075735.GA18878@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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: 1814 Lines: 45 On Thu, Jul 23, 2009 at 03:17:18PM -0700, Ken Chen wrote: > On Thu, Jul 23, 2009 at 12:57 AM, Bharata B > Rao wrote: > > Hi, > > > > Group scheduler fainess is broken since 2.6.29-rc1. git bisect led me > > to this commit: > > > > commit ec4e0e2fe018992d980910db901637c814575914 > > Author: Ken Chen > > Date: ? Tue Nov 18 22:41:57 2008 -0800 > > > > ? ?sched: fix inconsistency when redistribute per-cpu tg->cfs_rq shares > > > > ? ?Impact: make load-balancing more consistent > > .... > > > > ====================================================================== > > ? ? ? ? ? ? ? ? ? ? ? ?% CPU time division b/n groups > > Group ? ? ? ? ? 2.6.29-rc1 ? ? ? ? ? ? ?2.6.29-rc1 w/o the above patch > > ====================================================================== > > a with 8 tasks ?44 ? ? ? ? ? ? ? ? ? ? ?31 > > b with 5 tasks ?32 ? ? ? ? ? ? ? ? ? ? ?34 > > c with 3 tasks ?22 ? ? ? ? ? ? ? ? ? ? ?34 > > ====================================================================== > > All groups had equal shares. > > What value did you use for each task_group's share? For very large > value of tg->shares, it could be that all of the boost went to one CPU > and subsequently causes load-balancer to shuffle tasks around. Do you > see any unexpected task migration? Used default 1024 for each group. Without your patch, each of the tasks see around 165 migrations during a 60s run, but with your patch, they see 125 migrations (as per se.nr_migrations). I am using a 8CPU machine here. Regards, Bharata. -- 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/