From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754415AbZBOLBp (ORCPT ); Sun, 15 Feb 2009 06:01:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752648AbZBOLBg (ORCPT ); Sun, 15 Feb 2009 06:01:36 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:45702 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752587AbZBOLBf (ORCPT ); Sun, 15 Feb 2009 06:01:35 -0500 Date: Sun, 15 Feb 2009 12:01:04 +0100 From: Ingo Molnar To: Damien Wyart , Peter Zijlstra , Mike Galbraith , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List Subject: Re: [Bug #12650] Strange load average and ksoftirqd behavior with 2.6.29-rc2-git1 Message-ID: <20090215110104.GB31351@elte.hu> References: <20090215080941.GA2295@localhost.localdomain> <20090215090026.GA31147@elte.hu> <20090215095128.GA3234@localhost.localdomain> <20090215101351.GA23274@elte.hu> <20090215103445.GA2335@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090215103445.GA2335@localhost.localdomain> 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: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Damien Wyart wrote: > So I followed the tracing steps in the tutorial (with the 1 sec sleep), > which gave me this: > http://damien.wyart.free.fr/trace_2.6.29-rc5_ksoftirqd_prob.txt.gz thanks. There's definitely some weirdness visible in the trace, for example: 0) gpm-1879 => ksoftir-4 ------------------------------------------ 0) 0.964 us | finish_task_switch(); 0) ! 1768184 us | } 0) | do_softirq() { 0) | __do_softirq() { 0) | rcu_process_callbacks() { the 1.7 seconds 'overhead' there must be a fluke - you'd notice it if ksoftirqd _really_ took that much time to execute. One possibility for these symptoms would be broken scheduler timestamps. Could you enable absolute timestamp printing via: echo funcgraph-abstime > trace_options Also, my guess is that if you boot via idle=poll, the symptoms go away. This would strengthen the suspicion that it's scheduler-clock troubles. Ingo