From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933072Ab2AFIPo (ORCPT ); Fri, 6 Jan 2012 03:15:44 -0500 Received: from mga11.intel.com ([192.55.52.93]:45187 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932909Ab2AFIPm (ORCPT ); Fri, 6 Jan 2012 03:15:42 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="104127421" Subject: Re: [tip:sched/urgent] sched: Fix select_idle_sibling() regression in selecting an idle SMT sibling From: "Alex,Shi" To: Suresh Siddha Cc: Peter Zijlstra , "mingo@redhat.com" , "hpa@zytor.com" , "linux-kernel@vger.kernel.org" , "efault@gmx.de" , "tglx@linutronix.de" , "mingo@elte.hu" , "linux-tip-commits@vger.kernel.org" , "Li, Shaohua" , "Chen, Tim C" , "Huang, Ying" In-Reply-To: <1324665814.4167.32.camel@sbsiddha-desk.sc.intel.com> References: <1323978421.1984.244.camel@sbsiddha-desk.sc.intel.com> <1324471944.10752.8.camel@twins> <1324496556.21294.11.camel@sbsiddha-desk.sc.intel.com> <1324517502.17054.174.camel@debian> <1324519393.21294.20.camel@sbsiddha-desk.sc.intel.com> <1324520161.17054.190.camel@debian> <1324665814.4167.32.camel@sbsiddha-desk.sc.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 06 Jan 2012 16:14:13 +0800 Message-ID: <1325837653.4748.2.camel@debian> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-12-23 at 10:43 -0800, Suresh Siddha wrote: > On Wed, 2011-12-21 at 18:16 -0800, Shi, Alex wrote: > > On Thu, 2011-12-22 at 10:03 +0800, Siddha, Suresh B wrote: > > > On Wed, 2011-12-21 at 17:31 -0800, Shi, Alex wrote: > > > > This patch partly fixed a performance regression that triggered by > > > > 4dcfe1025b513c2c, but issue still exists. > > > > > > So how much was the regression caused by the commit 4dcfe1025b513c2c and > > > how much did we recover with this fix I posted. If we are talking about > > > the regression caused by this single commit 4dcfe1025b513c2c, then I > > > don't know of any other related fixes other than the recent fix we > > > pushed upstream (ab2789213d224202237292d78aaa0c386c7b28b2). > > > > A little complex for the whole thing. > > on 4 sockets EX machine, 3~5% hackbench thread regression due to 4dcfe > > can be recovered by ab2789. > > > > But on 2 sockets SNB machine, 1024 clients loop netperf TCP-RR has about > > 9% regression. and your patch seem recover 2~3%. > > > > And on a 2 sockets nhm, one of our private benchmark was impact much 20 > > +% regression. that benchmark just run 4 process, each of process open a > > thread, and the thread tasks is to locate randomly pages and than read > > from 4 times/write 1 time data into a page. The ab2789 commit seems no > > help our benchmark. > > Ok. Can you please try couple of experiments with two kernels? Two > kernels being the base kernel (prior to 4dcfe1025b513c2c) and the second > kernel with the commit ab2789213d224202237292d78aaa0c386c7b28b2. > > One experiment with p-states turned off and the second experiment with > c-states turned off. I did testing on both of kernel with setting 'performance' gov for all CPU P-states, and disable cpuidle by setting cpuidle.off=1 in cmdline. But didn't find measurable impact on performance result. > > I suspect mostly deeper core c-states might be contributing to the > behavior that you are seeing. > > thanks, > suresh >