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Date:   Fri, 13 Oct 2023 19:40:58 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Namhyung Kim <namhyung@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
Subject: Re: [PATCH] perf bench sched pipe: Add -G/--cgroups option
Message-ID: <ZSnHek1HlQTkfjhG@kernel.org>
References: <20231004204741.985422-1-namhyung@kernel.org>
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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?

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 :-\

- Arnaldo