From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jakub Kicinski <kubakici@wp.pl>
Subject: Re: [PATCH bpf-next v2 1/2] trace_helpers.c: Add helpers to poll
 multiple perf FDs for events
Date: Mon, 4 Jun 2018 15:26:02 -0700
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Cc: netdev@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@toke.dk>
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On Mon, 04 Jun 2018 18:33:56 +0200, Toke H=C3=B8iland-J=C3=B8rgensen 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.
>=20
> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.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...