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From:   Jiri Olsa <olsajiri@gmail.com>
Date:   Sat, 1 Oct 2022 15:57:54 +0200
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Jiri Olsa <olsajiri@gmail.com>, Tejun Heo <tj@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        cgroups <cgroups@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users <linux-perf-users@vger.kernel.org>,
        Song Liu <songliubraving@fb.com>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH] perf stat: Support old kernels for bperf cgroup counting
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On Fri, Sep 30, 2022 at 02:56:40PM -0700, Namhyung Kim wrote:
> Hi Jiri,
> 
> On Fri, Sep 30, 2022 at 2:44 PM Jiri Olsa <olsajiri@gmail.com> 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!
> >
> > could you please paste the cgroup tree link?
> 
> Do you mean this?
> 
>   https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git

yea, wanted to try that.. I cherry-picked the 7f203bc89eb6 ;-)

thanks,
jirka

> 
> Thanks,.
> Namhyung