From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934489AbXGZVcT (ORCPT ); Thu, 26 Jul 2007 17:32:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763253AbXGZVcI (ORCPT ); Thu, 26 Jul 2007 17:32:08 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:46810 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759833AbXGZVcG (ORCPT ); Thu, 26 Jul 2007 17:32:06 -0400 Date: Thu, 26 Jul 2007 23:31:54 +0200 From: Ingo Molnar To: Tong Li Cc: linux-kernel@vger.kernel.org, Chris Snook Subject: Re: [RFC] scheduler: improve SMP fairness in CFS Message-ID: <20070726213154.GA26569@elte.hu> References: <20070725110159.GA15076@elte.hu> <20070725120358.GA30755@elte.hu> <20070725192442.GC4463@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Tong Li wrote: > > you need to measure it over longer periods of time. Its not worth > > balancing for such a thing in any high-frequency manner. (we'd trash > > the cache constantly migrating tasks back and forth.) > > I have some data below, but before that, I'd like to say, at the same > load balancing rate, my proposed approach would allow us to have > fairness on the order of seconds. I'm less concerned about trashing > the cache. The important thing is to have a knob that allow users to > trade off fairness and performance based on their needs. [...] such a knob already exists to a certain degree, but i havent tested its full effects on SMP fairness yet. If you pull my scheduler tree: git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched.git and if you enable CONFIG_SCHED_DEBUG, then all the sched-domain parameters become runtime tunable under /proc/sys/cpu*. Could you try to increase the cross-CPU rebalancing frequency and see how it impacts the precision of your measurement? Tune 'min_interval' and 'max_interval' down to increase the frequency of rebalancing. Ingo