From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759100AbYDUTof (ORCPT ); Mon, 21 Apr 2008 15:44:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758073AbYDUTo0 (ORCPT ); Mon, 21 Apr 2008 15:44:26 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:54102 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756768AbYDUToZ (ORCPT ); Mon, 21 Apr 2008 15:44:25 -0400 Date: Mon, 21 Apr 2008 21:43:59 +0200 From: Ingo Molnar To: Frans Pop Cc: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Peter Zijlstra , Mike Galbraith , Richard Jonsson , "Rafael J. Wysocki" Subject: Re: [git pull] scheduler changes for v2.6.26 Message-ID: <20080421194359.GD8770@elte.hu> References: <20080419181304.GB21353@elte.hu> <200804192147.43719.elendil@planet.nl> <20080421123903.GE9554@elte.hu> <200804211831.29976.elendil@planet.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200804211831.29976.elendil@planet.nl> User-Agent: Mutt/1.5.17 (2007-11-01) 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: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Frans Pop wrote: > > It would be nice if you could try sched-devel/latest because it has > > an improved ftrace "sched_switch" tracer where you can generate much > > longer traces of this incident. Try the new /debug/trace_entries > > runtime tunable. > > I'll try to get the trace and will reply on the private thread we had. > I may need additional instructions though. you could also reply to this thread if you dont mind, so that others can chime in too. the 700-800 msecs of delays you see are very "brutal" so there must be something fundamentally wrong going on here. Could you first check (under sched-devel/latest) the quality of your sched-clock, via running this script: http://people.redhat.com/mingo/cfs-scheduler/tools/watch-rq-clock.sh if you run it, it should output ~1000 msecs periods every second: europe:~> watch-rq-clock.sh 1002.115042 1005.509851 1004.187275 1004.409980 1004.430264 1004.445508 if it's way too 'slow', say it only 100 msecs per second, then the scheduler clock is mis-measuring time and what the scheduler thinks to be a 40 msecs delay might become a 400 msecs delay. Ingo