From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753919Ab2DPMgT (ORCPT ); Mon, 16 Apr 2012 08:36:19 -0400 Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:34665 "EHLO e06smtp16.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753792Ab2DPMgP convert rfc822-to-8bit (ORCPT ); Mon, 16 Apr 2012 08:36:15 -0400 Date: Mon, 16 Apr 2012 14:36:06 +0200 From: Martin Schwidefsky To: Bas van der Oest Cc: linux-kernel@vger.kernel.org Subject: Re: /proc/stat information incorrect Message-ID: <20120416143606.2ee7c571@de.ibm.com> In-Reply-To: References: Organization: IBM Corporation X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT x-cbid: 12041612-3548-0000-0000-000001A1718C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 16 Apr 2012 10:04:48 +0200 Bas van der Oest wrote: > After dropping some zero columns and taking the difference between the > statistics the reformatted result is: >        user    nice    system  idle    iowait  irq     softirq sum > cpu     5       0       434     7676    0       0       53      8168 > cpu0    0       0       0       1067    0       0       0       1067 > cpu1    0       0       1       1070    0       0       0       1071 > cpu2    0       0       0       1071    0       0       0       1071 > cpu3    1       0       0       1070    0       0       0       1071 > cpu4    1       0       94      974     0       0       0       1069 > cpu5    2       0       92      535     0       0       52      681 > cpu6    0       0       82      987     0       0       0       1069 > cpu7    1       0       165     905     0       0       0       1071 > > I added a sum column which totals the time spent in the different > modes. The above table now shows how long each CPU was in what mode > for how long. > Now I am wondering how it is possible that CPU5 has spent much less > time than all the other CPUs. I expected that all CPUs spent around > the same time (10s). This time includes idle time so this is not > related to the difference in active/idle CPUs. > > I know for a fact that this effect is related to which CPU is handling > my IRQs; this effect happens to all CPUs if I map the interrupts to > that particular CPU. > I looked up the scheduler's statistics handling in the kernel source > but was not able to find any cause for the above mentioned effect. > > Can anyone reproduce this behaviour? > Does anyone know where/what might be the cause of this? Assuming that you are on a recent kernel (>= 3.2), could you please try to revoke git commit a25cac5198d4ff28 "proc: Consider NO_HZ when printing idle and iowait times" and try again ? -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.