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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Fri, 30 Sep 2022 13:30:18 -0700
Message-ID: <CAM9d7chMdGwxED8rt6-DWDCnRrbuNAJFFty3i5uqqeTBZJFzTA@mail.gmail.com>
Subject: Re: [PATCH] perf stat: Support old kernels for bperf cgroup counting
To:     Tejun Heo <tj@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
        Song Liu <songliubraving@fb.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        cgroups <cgroups@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users <linux-perf-users@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>
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On Fri, Sep 23, 2022 at 8:22 PM Tejun Heo <tj@kernel.org> wrote:
>
> On Wed, Sep 21, 2022 at 09:14:35PM -0700, Namhyung Kim wrote:
> > The recent change in the cgroup will break the backward compatiblity in
> > the BPF program.  It should support both old and new kernels using BPF
> > CO-RE technique.
> >
> > Like the task_struct->__state handling in the offcpu analysis, we can
> > check the field name in the cgroup struct.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> > Arnaldo, I think this should go through the cgroup tree since it depends
> > on the earlier change there.  I don't think it'd conflict with other
> > perf changes but please let me know if you see any trouble, thanks!
>
> FWIW, looks fine to me and I'd be happy to route this through the cgroup
> tree once it gets acked.

Thanks Tejun!

Can any perf + bpf folks take a look?