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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Fri, 13 Oct 2023 15:57:27 -0700
Message-ID: <CAM9d7cip5qmPRhWF37JH_21Q8SjKQCTBVyF_PLE-ytTFOwpasg@mail.gmail.com>
Subject: Re: [PATCH] perf bench sched pipe: Add -G/--cgroups option
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org
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Hi Arnaldo,

On Fri, Oct 13, 2023 at 3:41 PM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Wed, Oct 04, 2023 at 01:47:41PM -0700, Namhyung Kim escreveu:
> > The -G/--cgroups option is to put sender and receiver in different
> > cgroups in order to measure cgroup context switch overheads.
> >
> > Users need to make sure the cgroups exist and accessible.
> >
> >   # perf stat -e context-switches,cgroup-switches \
> >   > taskset -c 0 perf bench sched pipe -l 10000 > /dev/null
> >
> >    Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000':
> >
> >               20,001      context-switches
> >                    2      cgroup-switches
> >
> >          0.053449651 seconds time elapsed
> >
> >          0.011286000 seconds user
> >          0.041869000 seconds sys
> >
> >   # perf stat -e context-switches,cgroup-switches \
> >   > taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB > /dev/null
> >
> >    Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB':
> >
> >               20,001      context-switches
> >               20,001      cgroup-switches
> >
> >          0.052768627 seconds time elapsed
>
> So I tried with:
>
> [root@quaco ~]# perf bench sched pipe -G system.slice,user.slice
> # Running 'sched/pipe' benchmark:
> cannot enter to cgroup: system.slice
> cannot enter to cgroup: user.slice
> # Executed 1000000 pipe operations between two processes
>
>      Total time: 6.301 [sec]
>
>        6.301478 usecs/op
>          158692 ops/sec
> [root@quaco ~]#
>
> Should't it bail out when not managing to enter the cgroups?

Hmm.. right.  Will fix.

>
> Also:
>
> [root@quaco ~]# mkdir /sys/fs/cgroup/AAA
> [root@quaco ~]# mkdir /sys/fs/cgroup/BBB
> [root@quaco ~]#
> [root@quaco ~]# perf bench sched pipe -G AAA,BBB
> # Running 'sched/pipe' benchmark:
> cannot enter to cgroup: AAA
> cannot enter to cgroup: BBB
> # Executed 1000000 pipe operations between two processes
>
>      Total time: 6.397 [sec]
>
>        6.397830 usecs/op
>          156302 ops/sec
> [root@quaco ~]#
>
> -rw-r--r--. 1 root root 0 Oct 13 19:22 /sys/fs/cgroup/AAA/cgroup.procs
> [root@quaco ~]# ls -la /sys/fs/cgroup/AAA/cgroup.threads
> -rw-r--r--. 1 root root 0 Oct 13 19:22 /sys/fs/cgroup/AAA/cgroup.threads
> [root@quaco ~]# ls -la /sys/fs/cgroup/BBB/cgroup.threads
> -rw-r--r--. 1 root root 0 Oct 13 19:22 /sys/fs/cgroup/BBB/cgroup.threads
> [root@quaco ~]# ls -la /sys/fs/cgroup/BBB/cgroup.procs
> -rw-r--r--. 1 root root 0 Oct 13 19:22 /sys/fs/cgroup/BBB/cgroup.procs
> [root@quaco ~]#
>
> [root@quaco ~]# perf bench sched pipe -G AAA,BBB
> # Running 'sched/pipe' benchmark:
> cannot enter to cgroup: AAA (written=-1, len=6, errno=Operation not supported)
> cannot enter to cgroup: BBB (written=-1, len=6, errno=Operation not supported)
> # Executed 1000000 pipe operations between two processes
>
>      Total time: 6.303 [sec]
>
>        6.303221 usecs/op
>          158649 ops/sec
> [root@quaco ~]#
>
> I'm certainly missing something here :-\

Try to enable some cgroup controllers first.  Like

  # echo +cpu > /sys/fs/cgroup/AAA/cgroup.subtree_control
  # echo +cpu > /sys/fs/cgroup/BBB/cgroup.subtree_control

Thanks,
Namhyung