Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <CADjb_WQ0wFgZWBo0Xo1Q+NWS6vF0BSs5H0ho+5FM82Mu-JVYoQ@mail.gmail.com>
 <787302f0-670f-fadf-14e6-ea0a73603d77@arm.com> <60febadb-df21-a44b-d282-e43c104d2497@arm.com>
In-Reply-To: <60febadb-df21-a44b-d282-e43c104d2497@arm.com>
From:   Chen Yu <yu.chen.surf@gmail.com>
Date:   Wed, 19 Feb 2020 18:01:58 +0800
Message-ID: <CADjb_WRg-kbWCoPcds82SGFUfSpkvCQytfjvZV674NxOuTRE3Q@mail.gmail.com>
Subject: Re: [RFC] Display the cpu of sched domain in procfs
To:     Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc:     Valentin Schneider <valentin.schneider@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Mel Gorman <mgorman@suse.de>, Tony Luck <tony.luck@intel.com>,
        Aubrey Li <aubrey.li@linux.intel.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Borislav Petkov <bp@suse.de>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Dietmar,

On Wed, Feb 19, 2020 at 4:53 PM Dietmar Eggemann
<dietmar.eggemann@arm.com> wrote:
>
> On 19/02/2020 09:13, Valentin Schneider wrote:
> > Hi,
> >
> > On 19/02/2020 07:15, Chen Yu wrote:
> >> Problem:
> >> sched domain topology is not always consistent with the CPU topology exposed at
> >> /sys/devices/system/cpu/cpuX/topology,  which makes it
> >> hard for monitor tools to distinguish the CPUs among different sched domains.
> >>
> >> For example, on x86 if there are NUMA nodes within a package, say,
> >> SNC(Sub-Numa-Cluster),
> >> then there would be no die sched domain but only NUMA sched domains
> >> created. As a result,
> >> you don't know what the sched domain hierarchical is by only looking
> >> at /sys/devices/system/cpu/cpuX/topology.
> >>
> >> Although by appending sched_debug in command line would show the sched
> >> domain CPU topology,
> >> it is only printed once during boot up, which makes it hard to track
> >> at run-time.
>
> What about /proc/schedstat?
>
That's it!  I did not notice it before, this should work although the
user space might
need to parse the format.


-- 
Thanks,
Chenyu
> E.g. on Intel Xeon CPU E5-2690 v2
>
> $ cat /proc/schedstat | head
> version 15
> timestamp 4486170100
> cpu0 0 0 0 0 0 0 59501267037720 16902762382193 1319621004
> domain0 00,00100001 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> domain1 00,3ff003ff 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> domain2 ff,ffffffff 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
>
>         ^^^^^^^^^^^
>
> cpu1 0 0 0 0 0 0 56045879920164 16758983055410 1318489275
> domain0 00,00200002 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> domain1 00,3ff003ff 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> domain2 ff,ffffffff 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> ...
>