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

[Song Liu <songliubraving@fb.com>]

> On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andriin@fb.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@fb.com>

Acked-by: Song Liu <songliubraving@fb.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(-)