From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754874AbXJ2WNk (ORCPT ); Mon, 29 Oct 2007 18:13:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752868AbXJ2WNc (ORCPT ); Mon, 29 Oct 2007 18:13:32 -0400 Received: from E23SMTP03.au.ibm.com ([202.81.18.172]:36249 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900AbXJ2WNb (ORCPT ); Mon, 29 Oct 2007 18:13:31 -0400 Date: Tue, 30 Oct 2007 03:13:22 +0530 From: Balbir Singh To: Ingo Molnar Cc: Frans Pop , Christian Borntraeger , Chuck Ebbert , Greg KH , stable@kernel.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [stable] 2.6.23 regression: top displaying 9999% CPU usage Message-ID: <20071029214321.GA25669@linux.vnet.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <200710122231.50739.elendil@planet.nl> <200710161234.35529.borntraeger@de.ibm.com> <4714B5BF.1090001@linux.vnet.ibm.com> <200710291305.52992.elendil@planet.nl> <4725D2A5.1050908@linux.vnet.ibm.com> <20071029200425.GA830@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071029200425.GA830@elte.hu> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 29, 2007 at 09:04:25PM +0100, Ingo Molnar wrote: > > * Balbir Singh wrote: > > > We'll I initially thought of it and then I remembered that the > > regression occurs only when the accounting itself is inaccurate. I am > > tempted to ack the removal, but I would like to get input from others. > > Meanwhile, I'll try and see if I can fix the problem > > i've got a patch from Peter queued up. (see below) This should fix the > main issue. > > Ingo > We'll also need this additional patch (untested), but in the long run I think the approach needs to be 1. Update stime and utime at the time of context switching -- keep it in sync with p->sum_exec_runtime 2. Keep track of system/user context at system call entry points Extend Peter's patch to fix accounting issues. Signed-off-by: Balbir Singh --- fs/proc/array.c | 3 ++- include/linux/sched.h | 2 +- kernel/fork.c | 1 + 3 files changed, 4 insertions(+), 2 deletions(-) diff -puN fs/proc/array.c~fix-accounting-issue-extended fs/proc/array.c --- 2.6.24-rc1/fs/proc/array.c~fix-accounting-issue-extended 2007-10-30 03:08:18.000000000 +0530 +++ 2.6.24-rc1-balbir/fs/proc/array.c 2007-10-30 03:09:46.000000000 +0530 @@ -374,7 +374,8 @@ static cputime_t task_stime(struct task_ stime = nsec_to_clock_t(p->se.sum_exec_runtime) - cputime_to_clock_t(task_utime(p)); - return clock_t_to_cputime(stime); + p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime)); + return p->prev_stime; } #endif diff -puN include/linux/sched.h~fix-accounting-issue-extended include/linux/sched.h --- 2.6.24-rc1/include/linux/sched.h~fix-accounting-issue-extended 2007-10-30 03:08:18.000000000 +0530 +++ 2.6.24-rc1-balbir/include/linux/sched.h 2007-10-30 03:08:32.000000000 +0530 @@ -1004,7 +1004,7 @@ struct task_struct { unsigned int rt_priority; cputime_t utime, stime, utimescaled, stimescaled; cputime_t gtime; - cputime_t prev_utime; + cputime_t prev_utime, prev_stime; unsigned long nvcsw, nivcsw; /* context switch counts */ struct timespec start_time; /* monotonic time */ struct timespec real_start_time; /* boot based time */ diff -puN kernel/fork.c~fix-accounting-issue-extended kernel/fork.c --- 2.6.24-rc1/kernel/fork.c~fix-accounting-issue-extended 2007-10-30 03:08:18.000000000 +0530 +++ 2.6.24-rc1-balbir/kernel/fork.c 2007-10-30 03:08:42.000000000 +0530 @@ -1057,6 +1057,7 @@ static struct task_struct *copy_process( p->utimescaled = cputime_zero; p->stimescaled = cputime_zero; p->prev_utime = cputime_zero; + p->prev_stime = cputime_zero; #ifdef CONFIG_TASK_XACCT p->rchar = 0; /* I/O counter: bytes read */ _ -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL