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Date:   Fri, 21 Aug 2020 14:31:33 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Kernel Team <kernel-team@...com>,
        Alan Maguire <alan.maguire@...cle.com>
Subject: Re: [PATCH v2 bpf-next] libbpf: add perf_buffer APIs for better
 integration with outside epoll loop

On Fri, Aug 21, 2020 at 10:06 AM Andrii Nakryiko <andriin@...com> wrote:
>
> Add a set of APIs to perf_buffer manage to allow applications to integrate
> perf buffer polling into existing epoll-based infrastructure. One example is
> applications using libevent already and wanting to plug perf_buffer polling,
> instead of relying on perf_buffer__poll() and waste an extra thread to do it.
> But perf_buffer is still extremely useful to set up and consume perf buffer
> rings even for such use cases.
>
> So to accomodate such new use cases, add three new APIs:
>   - perf_buffer__buffer_cnt() returns number of per-CPU buffers maintained by
>     given instance of perf_buffer manager;
>   - perf_buffer__buffer_fd() returns FD of perf_event corresponding to
>     a specified per-CPU buffer; this FD is then polled independently;
>   - perf_buffer__consume_buffer() consumes data from single per-CPU buffer,
>     identified by its slot index.
>
> To support a simpler, but less efficient, way to integrate perf_buffer into
> external polling logic, also expose underlying epoll FD through
> perf_buffer__epoll_fd() API. It will need to be followed by
> perf_buffer__poll(), wasting extra syscall, or perf_buffer__consume(), wasting
> CPU to iterate buffers with no data. But could be simpler and more convenient
> for some cases.
>
> These APIs allow for great flexiblity, but do not sacrifice general usability
> of perf_buffer.
>
> Also exercise and check new APIs in perf_buffer selftest.
>
> Reviewed-by: Alan Maguire <alan.maguire@...cle.com>
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Applied. Thanks

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