linux-kernel - Re: [PATCHSET v2 0/3] perf stat: Enable BPF counters with --for-each-cgroup

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Message-ID: <CAM9d7cj2UhQsd2vx8_C8C_CEW2QQbzs741jCn7f7g-e0i9OiOg@mail.gmail.com>
Date:   Wed, 16 Jun 2021 09:33:42 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Song Liu <songliubraving@...com>
Subject: Re: [PATCHSET v2 0/3] perf stat: Enable BPF counters with --for-each-cgroup

Hi Peter,

On Wed, Jun 16, 2021 at 8:14 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Mon, Jun 14, 2021 at 06:17:21PM -0700, Namhyung Kim wrote:
> > Current limitations are:
> >  * it doesn't support cgroup hierarchy
>
> That seems unfortunate; there's no bpf helper to iterate cgroup
> hierarchy?

I couldn't find one..

>
> >  * there's no reliable way to trigger running the BPF program
>
> You can't attach to the PERF_COUNT_SW_CGROUP_SWITCHES event?

I did it.  But the BPF test run seems not to work with perf_event.
So it needs to trigger a cgroup switch manually..

Thanks,
Namhyung