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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Wed, 23 Sep 2020 07:55:26 +0900
Message-ID: <CAM9d7ch5ZejOpDgj6fAGcGHAcbgEV6dZ4SfArw7xDMPKkTphvQ@mail.gmail.com>
Subject: Re: [PATCH 2/5] perf stat: Add --for-each-cgroup option
To:     Stephane Eranian <eranian@google.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Ian Rogers <irogers@google.com>
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Hi Stephane,

On Wed, Sep 23, 2020 at 6:52 AM Stephane Eranian <eranian@google.com> wrote:
>
> Hi,
>
> On Mon, Sep 21, 2020 at 2:46 AM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > The --for-each-cgroup option is a syntax sugar to monitor large number
> > of cgroups easily.  Current command line requires to list all the
> > events and cgroups even if users want to monitor same events for each
> > cgroup.  This patch addresses that usage by copying given events for
> > each cgroup on user's behalf.
> >
> > For instance, if they want to monitor 6 events for 200 cgroups each
> > they should write 1200 event names (with -e) AND 1200 cgroup names
> > (with -G) on the command line.  But with this change, they can just
> > specify 6 events and 200 cgroups with a new option.
> >
> > A simpler example below: It wants to measure 3 events for 2 cgroups
> > ('A' and 'B').  The result is that total 6 events are counted like
> > below.
> >
> >   $ ./perf stat -a -e cpu-clock,cycles,instructions --for-each-cgroup A,B sleep 1
> >
> You could also do it by keeping the -G option and providing
> --for-each-cgroup as a modifier
> of the behavior of -G:
>
> $ ./perf stat -a -e cpu-clock,cycles,instructions --for-each-cgroup -G
>  A,B sleep 1
>
> That way, you do not have to handle the case where both are used.
> And it makes transitioning to the new style simpler, i.e., the -G
> option remains, just need
> to trim the number of cgroups to 200 in your example.
>
> Just a suggestion.

Thanks for the suggestion.  Actually that's the approach I took
in my v1 submission.  And Jiri suggested the current way.
Personally I'm fine with either.

Thanks
Namhyung