From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754211Ab2GRMWq (ORCPT ); Wed, 18 Jul 2012 08:22:46 -0400 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:57606 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752018Ab2GRMWn (ORCPT ); Wed, 18 Jul 2012 08:22:43 -0400 Message-ID: <5006AA40.1090408@linux.vnet.ibm.com> Date: Wed, 18 Jul 2012 17:51:20 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Martin Schwidefsky CC: Michal Hocko , Thomas Gleixner , linux-kernel , "akpm@linux-foundation.org" Subject: Re: [PATCH v2] fix idle ticks in cpu summary line of /proc/stat 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> <4F5F0623.6080702@linux.vnet.ibm.com> <20120718135255.1eafb680@de.ibm.com> In-Reply-To: <20120718135255.1eafb680@de.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12071812-2000-0000-0000-0000084FDF19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/18/2012 05:22 PM, Martin Schwidefsky wrote: > On Tue, 13 Mar 2012 14:02:35 +0530 > "Srivatsa S. Bhat" wrote: > >> On 03/13/2012 01:37 PM, 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 >>> Signed-off-by: Michal Hocko >>> --- >>> fs/proc/stat.c | 14 ++++++++++---- >>> 1 files changed, 10 insertions(+), 4 deletions(-) >>> >>> diff --git a/fs/proc/stat.c b/fs/proc/stat.c >>> index 121f77c..62bda24 100644 >>> --- a/fs/proc/stat.c >>> +++ b/fs/proc/stat.c >>> @@ -24,10 +24,13 @@ >>> >>> static u64 get_idle_time(int cpu) >>> { >>> - u64 idle, idle_time = get_cpu_idle_time_us(cpu, NULL); >>> + u64 idle, idle_time = -1ULL; >>> + >>> + if (cpu_online(cpu)) >>> + idle_time = get_cpu_idle_time_us(cpu, NULL); >>> >>> if (idle_time == -1ULL) { >>> - /* !NO_HZ so we can rely on cpustat.idle */ >>> + /* !NO_HZ or cpu offline so we can rely on cpustat.idle */ >>> idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE]; >>> idle += arch_idle_time(cpu); >>> } else >>> @@ -38,10 +41,13 @@ static u64 get_idle_time(int cpu) >>> >>> static u64 get_iowait_time(int cpu) >>> { >>> - u64 iowait, iowait_time = get_cpu_iowait_time_us(cpu, NULL); >>> + u64 iowait, iowait_time = -1ULL; >>> + >>> + if (cpu_online(cpu)) >>> + iowait_time = get_cpu_iowait_time_us(cpu, NULL); >>> >>> if (iowait_time == -1ULL) >>> - /* !NO_HZ so we can rely on cpustat.iowait */ >>> + /* !NO_HZ or cpu offline so we can rely on cpustat.iowait */ >>> iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT]; >>> else >>> iowait = usecs_to_cputime64(iowait_time); >> >> >> >> Yeah, this looks much better.. >> >> Reviewed-by: Srivatsa S. Bhat > > What happened to this patch? The fix for s390 (git commit cb85a6ed67e979c59 > "proc: stats: Use arch_idle_time for idle and iowait times if available" > is upstream but the fix for non-s390 systems is missing, no? > Oh, right! Thomas, could you kindly pick up Michal's patch please? Martin had outlined the relationship between the 2 patches here: http://thread.gmane.org/gmane.linux.kernel/1265374/focus=1276336 Regards, Srivatsa S. Bhat