From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758975Ab2C2Kmf (ORCPT ); Thu, 29 Mar 2012 06:42:35 -0400 Received: from www.linutronix.de ([62.245.132.108]:51228 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752911Ab2C2Km2 (ORCPT ); Thu, 29 Mar 2012 06:42:28 -0400 Date: Thu, 29 Mar 2012 12:42:22 +0200 (CEST) From: Thomas Gleixner To: Michal Hocko cc: Martin Schwidefsky , "Srivatsa S. Bhat" , linux-kernel Subject: Re: [PATCH v2] fix idle ticks in cpu summary line of /proc/stat In-Reply-To: <20120313080748.GA7754@tiehlicka.suse.cz> Message-ID: References: <20120311182621.41674b39@de.ibm.com> <20120312121726.GA23608@tiehlicka.suse.cz> <20120312101739.26eb373e@de.ibm.com> <4F5E0CC1.6010102@linux.vnet.ibm.com> <20120312153906.GE3994@tiehlicka.suse.cz> <20120312164145.5110ed5c@de.ibm.com> <20120313080748.GA7754@tiehlicka.suse.cz> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Mar 2012, Michal Hocko wrote: > OK, so the updated version of the patch looks like this. I am sorry but > I had time to only compile test this... > --- > >From d12247f14c5f8b00ae97a87442f62e49227a759b Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 12 Mar 2012 13:11:38 +0100 > Subject: [PATCH] nohz: fix idle ticks in cpu summary line of /proc/stat > > Git commit 09a1d34f8535ecf9 "nohz: Make idle/iowait counter update > conditional" introduced a bug in regard to cpu hotplug. The effect is > that the number of idle ticks in the cpu summary line in /proc/stat is > still counting ticks for offline cpus. > > Reproduction is easy, just start a workload that keeps all cpus busy, > switch off one or more cpus and then watch the idle field in top. > On a dual-core with one cpu 100% busy and one offline cpu you will get > something like this: > > %Cpu(s): 48.7 us, 1.3 sy, 0.0 ni, 50.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st > > The problem is that an offline cpu still has ts->idle_active == 1. > To fix this we should make sure that the cpu is online when calling > get_cpu_idle_time_us and get_cpu_iowait_time_us. > > Cc: Thomas Gleixner > Cc: "Srivatsa S. Bhat" > Reported-by: Martin Schwidefsky Martin, does that solve the problem for you ? Thanks, tglx