Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753314AbZD2Jt6 (ORCPT ); Wed, 29 Apr 2009 05:49:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751779AbZD2Jtt (ORCPT ); Wed, 29 Apr 2009 05:49:49 -0400 Received: from mtagate7.de.ibm.com ([195.212.29.156]:58081 "EHLO mtagate7.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750858AbZD2Jts convert rfc822-to-8bit (ORCPT ); Wed, 29 Apr 2009 05:49:48 -0400 Date: Wed, 29 Apr 2009 11:48:01 +0200 From: Martin Schwidefsky To: Eric Dumazet Cc: Andrew Morton , Andrew Gallatin , linux-kernel@vger.kernel.org, rick.jones2@hp.com, brice@myri.com, Paul Mackerras , Benjamin Herrenschmidt , Ingo Molnar Subject: Re: [PATCH] sched: account system time properly Message-ID: <20090429114801.09637e46@skybase> In-Reply-To: <49F81BC3.2050805@cosmosbay.com> References: <49F078FA.6010507@myri.com> <20090428163004.46733752.akpm@linux-foundation.org> <49F7DF44.8090907@cosmosbay.com> <49F805C9.9070303@cosmosbay.com> <20090429100840.77359cae@skybase> <49F81BC3.2050805@cosmosbay.com> Organization: IBM Corporation X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2863 Lines: 71 On Wed, 29 Apr 2009 11:20:03 +0200 Eric Dumazet wrote: > Martin Schwidefsky a ?crit : > > On Wed, 29 Apr 2009 09:46:17 +0200 > > Eric Dumazet wrote: > > > >> Eric Dumazet a ?crit : > >>> Andrew Morton a ?crit : > >>> > >>> So, if IRQs are interrupting idle task, I guess if (p != rq->idle) will be false. > >>> > > > > If an IRQ interrupts the idle task the tick is supposed to be accounted > > as an idle tick. Only if the IRQ interrupted the system while it has > > been in hardirq or softirq processing then it should be accounted as > > system tick. > > > >> Maybe following patch is needed ? > >> > >> [PATCH] sched: account system time properly > >> > >> When idle task is interrupted by an IRQ, time accounting considers CPU is idle, > >> even while it should account for hard or softirq. > >> > >> Signed-off-by: Eric Dumazet > >> > >> diff --git a/kernel/sched.c b/kernel/sched.c > >> index b902e58..26efa47 100644 > >> --- a/kernel/sched.c > >> +++ b/kernel/sched.c > >> @@ -4732,7 +4732,7 @@ void account_process_tick(struct task_struct *p, int user_tick) > >> > >> if (user_tick) > >> account_user_time(p, one_jiffy, one_jiffy_scaled); > >> - else if (p != rq->idle) > >> + else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET)) > >> account_system_time(p, HARDIRQ_OFFSET, one_jiffy, > >> one_jiffy_scaled); > >> else > > > > That patch makes a lot of sense to me. Does it fix the problem? > > > > Yes it does, on my machine at least : > > 11:18:48 AM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle > 11:18:58 AM all 0.00 0.00 0.00 0.00 0.21 0.69 0.00 0.00 99.10 > 11:18:58 AM 0 0.00 0.00 0.00 0.00 1.70 5.50 0.00 0.00 92.80 << HERE >> > 11:18:58 AM 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 > 11:18:58 AM 7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 Very good. Acked-by: Martin Schwidefsky -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/