netdev - Re: [PATCH bpf-next v2 1/2] trace_helpers.c: Add helpers to poll multiple perf FDs for events

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Date:   Tue, 5 Jun 2018 11:27:20 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Toke Høiland-Jørgensen <toke@...e.dk>,
        Jakub Kicinski <kubakici@...pl>
Cc:     netdev@...r.kernel.org,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH bpf-next v2 1/2] trace_helpers.c: Add helpers to poll
 multiple perf FDs for events

On 06/05/2018 11:22 AM, Toke Høiland-Jørgensen wrote:
> Daniel Borkmann <daniel@...earbox.net> writes:
>> On 06/05/2018 12:26 AM, Jakub Kicinski wrote:
>>> On Mon, 04 Jun 2018 18:33:56 +0200, Toke Høiland-Jørgensen wrote:
>>>> This adds two new helper functions to trace_helpers that supports polling
>>>> multiple perf file descriptors for events. These are used to the XDP
>>>> perf_event_output example, which needs to work with one perf fd per CPU.
>>>>
>>>> Signed-off-by: Toke Høiland-Jørgensen <toke@...e.dk>
>>>
>>> Did you take a look at tools/bpf/bpftool/map_perf_ring.c ?
>>>
>>> I think the ability to poll multiple FDs could be generally useful and
>>> therefore better add it to libbpf.c than
>>> tools/testing/selftests/bpf/trace_helpers.c?  I'm not 100% sure myself...
>>
>> I think for it to land in libbpf this code needs to be more generalized
>> as it is right now and allowing for more flexibility like pinning RB
>> processing threads to CPUs, poll handling, etc.
> 
> Hmm, so how about we leave it in trace_helpers.c for now? I don't
> necessarily mind working on an addition to libbpf at some point, but
> don't have time to do so short term...

That's okay with me as well.