linux-kernel - Re: [PATCH] perf stat: Support old kernels for bperf cgroup counting

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Date:   Fri, 23 Sep 2022 17:22:51 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
        bpf@...r.kernel.org
Subject: Re: [PATCH] perf stat: Support old kernels for bperf cgroup counting

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@...nel.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