netdev - Re: [PATCH v2 bpf-next 1/3] libbpf: add perf buffer API

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Message-ID: <4D6ED1DE-A8F0-4531-BB0A-3C99E42BE60C@fb.com>
Date:   Wed, 26 Jun 2019 19:02:17 +0000
From:   Song Liu <songliubraving@...com>
To:     Andrii Nakryiko <andriin@...com>
CC:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 1/3] libbpf: add perf buffer API



> On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andriin@...com> wrote:
> 
> BPF_MAP_TYPE_PERF_EVENT_ARRAY map is often used to send data from BPF program
> to user space for additional processing. libbpf already has very low-level API
> to read single CPU perf buffer, bpf_perf_event_read_simple(), but it's hard to
> use and requires a lot of code to set everything up. This patch adds
> perf_buffer abstraction on top of it, abstracting setting up and polling
> per-CPU logic into simple and convenient API, similar to what BCC provides.
> 
> perf_buffer__new() sets up per-CPU ring buffers and updates corresponding BPF
> map entries. It accepts two user-provided callbacks: one for handling raw
> samples and one for get notifications of lost samples due to buffer overflow.
> 
> perf_buffer__poll() is used to fetch ring buffer data across all CPUs,
> utilizing epoll instance.
> 
> perf_buffer__free() does corresponding clean up and unsets FDs from BPF map.
> 
> All APIs are not thread-safe. User should ensure proper locking/coordination if
> used in multi-threaded set up.
> 
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Acked-by: Song Liu <songliubraving@...com>

> ---
> tools/lib/bpf/libbpf.c   | 282 +++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h   |  12 ++
> tools/lib/bpf/libbpf.map |   5 +-
> 3 files changed, 298 insertions(+), 1 deletion(-)