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From:   Song Liu <songliubraving@fb.com>
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
CC:     open list <linux-kernel@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
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        KP Singh <kpsingh@chromium.org>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
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Subject: Re: [PATCH bpf-next 5/5] selftests/bpf: add benchmark for uprobe vs.
 user_prog
Thread-Topic: [PATCH bpf-next 5/5] selftests/bpf: add benchmark for uprobe vs.
 user_prog
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Date:   Mon, 3 Aug 2020 04:47:47 +0000
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> On Aug 2, 2020, at 6:51 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> w=
rote:
>=20
> On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@fb.com> wrote:
>>=20
>> Add a benchmark to compare performance of
>>  1) uprobe;
>>  2) user program w/o args;
>>  3) user program w/ args;
>>  4) user program w/ args on random cpu.
>>=20
>=20
> Can you please add it to the existing benchmark runner instead, e.g.,
> along the other bench_trigger benchmarks? No need to re-implement
> benchmark setup. And also that would also allow to compare existing
> ways of cheaply triggering a program vs this new _USER program?

Will try.=20

>=20
> If the performance is not significantly better than other ways, do you
> think it still makes sense to add a new BPF program type? I think
> triggering KPROBE/TRACEPOINT from bpf_prog_test_run() would be very
> nice, maybe it's possible to add that instead of a new program type?
> Either way, let's see comparison with other program triggering
> mechanisms first.

Triggering KPROBE and TRACEPOINT from bpf_prog_test_run() will be useful.=20
But I don't think they can be used instead of user program, for a couple
reasons. First, KPROBE/TRACEPOINT may be triggered by other programs=20
running in the system, so user will have to filter those noise out in
each program. Second, it is not easy to specify CPU for KPROBE/TRACEPOINT,
while this feature could be useful in many cases, e.g. get stack trace=20
on a given CPU.=20

Thanks,
Song=