From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753489AbYI3LMs (ORCPT ); Tue, 30 Sep 2008 07:12:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752754AbYI3LMj (ORCPT ); Tue, 30 Sep 2008 07:12:39 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:47454 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752596AbYI3LMi (ORCPT ); Tue, 30 Sep 2008 07:12:38 -0400 Date: Tue, 30 Sep 2008 13:12:17 +0200 From: Ingo Molnar To: Chris Friesen Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Steven Rostedt Subject: Re: unpredictability in scheduler test results -- still present Message-ID: <20080930111217.GA21367@elte.hu> References: <48D2DA0D.4060300@nortel.com> <48DA5A84.8030704@nortel.com> <48DACF55.3070209@nortel.com> <20080927200433.GC28937@elte.hu> <48E0F7B9.3040301@nortel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48E0F7B9.3040301@nortel.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0021] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Chris Friesen wrote: > Ingo Molnar wrote: >> * Chris Friesen wrote: > >>> It turns out that disabling CONFIG_DYNAMIC_FTRACE makes the load >>> balancing problem go away and causes all cpus to be used. >>> >>> With this option enabled, the problem seems to be present as far back >>> as 2.6.27-rc2. (2.6.27-rc1 doesn't compile on my machine, and 2.6.26 >>> doesn't have ftrace). >>> >>> I have no idea why turning on dynamic ftrace would affect load >>> balancing behaviour, but it's very repeatable. The very first test >>> run after booting works fine, and all successive runs fail to balance >>> properly. > >> OTOH, what does 'truning on dftrace' exactly mean? Just enabling it in >> the .config, or also activating it via /debug/tracing/current_tracer? > > Just enabling it in the .config is enough to trigger the behaviour > change. I'm not explicitly activating any traces. ok, that would be a clear ftrace bug i guess? Ingo