Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758500AbZD2JX3 (ORCPT ); Wed, 29 Apr 2009 05:23:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756571AbZD2JWw (ORCPT ); Wed, 29 Apr 2009 05:22:52 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:46336 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758408AbZD2JWv convert rfc822-to-8bit (ORCPT ); Wed, 29 Apr 2009 05:22:51 -0400 Message-ID: <49F81BC3.2050805@cosmosbay.com> Date: Wed, 29 Apr 2009 11:20:03 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: Martin Schwidefsky 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 References: <49F078FA.6010507@myri.com> <20090428163004.46733752.akpm@linux-foundation.org> <49F7DF44.8090907@cosmosbay.com> <49F805C9.9070303@cosmosbay.com> <20090429100840.77359cae@skybase> In-Reply-To: <20090429100840.77359cae@skybase> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Wed, 29 Apr 2009 11:20:04 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2537 Lines: 61 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 -- 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/