linux-kernel - Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option

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Date:   Mon, 16 Oct 2023 17:34:59 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option

Em Mon, Oct 16, 2023 at 12:55:33PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Oct 16, 2023 at 12:51:52PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Now back at testing with with cgroups.

> Humm, even without the -G I get:

> [root@...e ~]# perf stat -e context-switches,cgroup-switches perf bench sched pipe  -l 10000
> # Running 'sched/pipe' benchmark:
> # Executed 10000 pipe operations between two processes
 
>      Total time: 0.082 [sec]
 
>        8.246400 usecs/op
>          121265 ops/sec
 
>  Performance counter stats for 'perf bench sched pipe -l 10000':
 
>             20,002      context-switches
>             20,002      cgroup-switches

Same number, but then I forgot to add the 'taskset -c 0' part of the
command line, if I have it:

[root@...e ~]# perf stat -e context-switches,cgroup-switches taskset -c 0 perf bench sched pipe -l 10000
# Running 'sched/pipe' benchmark:
# Executed 10000 pipe operations between two processes

     Total time: 0.072 [sec]

       7.231500 usecs/op
         138283 ops/sec

 Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000':

            20,002      context-switches
                 3      cgroup-switches

       0.082855113 seconds time elapsed

       0.007765000 seconds user
       0.074020000 seconds sys


[root@...e ~]# perf stat -e context-switches,cgroup-switches taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB
# Running 'sched/pipe' benchmark:
# Executed 10000 pipe operations between two processes

     Total time: 0.093 [sec]

       9.341800 usecs/op
         107045 ops/sec

 Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB':

            20,004      context-switches
            20,003      cgroup-switches

       0.103436330 seconds time elapsed

       0.018109000 seconds user
       0.063058000 seconds sys


[root@...e ~]#

I.e. it works as in your results, but can you please spell out why that
'taskset -c 0' is needed to get these results?

I wasn't expecting the same number of cgroup-switches when not using
'taskset -c 0' :-\

- Arnaldo