From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762121AbYEIPnA (ORCPT ); Fri, 9 May 2008 11:43:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753277AbYEIPmv (ORCPT ); Fri, 9 May 2008 11:42:51 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:33139 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752413AbYEIPmu (ORCPT ); Fri, 9 May 2008 11:42:50 -0400 Date: Fri, 9 May 2008 21:22:40 +0530 From: Srivatsa Vaddagiri To: "Zhang, Yanmin" Cc: Dhaval Giani , Peter Zijlstra , LKML , Ingo Molnar , Aneesh Kumar KV Subject: Re: volanoMark regression with kernel 2.6.26-rc1 Message-ID: <20080509155240.GH3612@linux.vnet.ibm.com> Reply-To: vatsa@linux.vnet.ibm.com References: <1210039590.3453.18.camel@ymzhang> <20080506115207.GA24862@linux.vnet.ibm.com> <20080507173357.GA4424@linux.vnet.ibm.com> <1210223914.3453.102.camel@ymzhang> <20080508054047.GD32729@linux.vnet.ibm.com> <1210226013.3453.113.camel@ymzhang> <20080508061125.GC3644@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080508061125.GC3644@linux.vnet.ibm.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 08, 2008 at 11:41:25AM +0530, Srivatsa Vaddagiri wrote: > The other combination that I am interested to know is when: > > CONFIG_FAIR_GROUP_SCHED=y and CONFIG_CGROUP_SCHED=y > > [i.e cgroup based scheduling rather than uid based scheduling. Former > should result in only one group at bootup] > > I will also try to get some numbers with this combination. I ran with that combination and here are some results: 2.6.25 (with CONFIG_USER_SCHED) Volanomark perf = 20436.6 (Avg of 10 runs) 2.6.26-rc1 + patches in Ingo's tree [1] as of Fri morning IST (abt 8 hrs before) (with CONFIG_CGROUP_SCHED) Volanomark perf = 21529.6 i.e CGROUP based grouping in 2.6.26-rc1 gives same (if not somewhat better) results as UID-based scheduling in 2.6.25. Yamin, Could you validate this as well? i.e just turn on cgroup-based grouping (CONFIG_CGROUP_SCHED) and check the resulting performance with 2625 you already have (using CONFIG_USER_SCHED). A) In 2.6.25, with UID based scheduling, CPU load = summation of task load B) In 2.6.26-rc1, with UID based scheduling, CPU load = summation of group weights C) In 2.6.26-rc1, with CGROUP based scheduling, CPU load = summation of task weights This change in definition of cpu load is affecting load balance routines (find_busiest_group et al). As a result, threads of volanomark benchmark aren't quickly spread across the cpus, resulting in slower performance. In case of B), cpu load can be low numbers (100 or 200), while in A or C, cpu load are large numbers. I think find_busiest_group() and related routines need to be "educated" to deal with such low numbers .. -- Regards, vatsa