linux-kernel - Re: [RFC 0/2] Introduce perf-stat -b for BPF programs

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Date:   Thu, 19 Nov 2020 11:52:46 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org
Subject: Re: [RFC 0/2] Introduce perf-stat -b for BPF programs

Em Wed, Nov 18, 2020 at 08:50:44PM -0800, Song Liu escreveu:
> This set introduces perf-stat -b option to count events for BPF programs.
> This is similar to bpftool-prog-profile. But perf-stat makes it much more
> flexible.
> 
> Sending as RFC because I would like comments on some key design choices:
>   1. We are using BPF skeletons here, which is by far the easiest way to
>      write and ship BPF programs. However, this requires bpftool, which
>      makes building perf slower.
>   2. A Makefile is added to tools/perf/util/bpf_skel/ to build bpftool,
>      and BPF skeletons. This keeps main perf Makefiles simple. But we may
>      not like it for some reason?

I'll review it in detail, but before that: thanks a lot for working on
this! Looks super cool from a first quick look. :-)

- Arnaldo
 
> Some known limitations (or work to be done):
>   1. Only counting events for one BPF program at a time.
>   2. Need extra logic in target__validate().

 
> Song Liu (2):
>   perf: support build BPF skeletons with perf
>   perf-stat: enable counting events for BPF programs
> 
>  tools/build/Makefile.feature                  |   3 +-
>  tools/perf/Makefile.config                    |   8 +
>  tools/perf/Makefile.perf                      |  15 +-
>  tools/perf/builtin-stat.c                     |  59 ++++-
>  tools/perf/util/Build                         |   1 +
>  tools/perf/util/bpf_counter.c                 | 215 ++++++++++++++++++
>  tools/perf/util/bpf_counter.h                 |  71 ++++++
>  tools/perf/util/bpf_skel/.gitignore           |   3 +
>  tools/perf/util/bpf_skel/Makefile             |  71 ++++++
>  .../util/bpf_skel/bpf_prog_profiler.bpf.c     |  96 ++++++++
>  tools/perf/util/bpf_skel/dummy.bpf.c          |  19 ++
>  tools/perf/util/evsel.c                       |  10 +
>  tools/perf/util/evsel.h                       |   5 +
>  tools/perf/util/target.h                      |   6 +
>  14 files changed, 571 insertions(+), 11 deletions(-)
>  create mode 100644 tools/perf/util/bpf_counter.c
>  create mode 100644 tools/perf/util/bpf_counter.h
>  create mode 100644 tools/perf/util/bpf_skel/.gitignore
>  create mode 100644 tools/perf/util/bpf_skel/Makefile
>  create mode 100644 tools/perf/util/bpf_skel/bpf_prog_profiler.bpf.c
>  create mode 100644 tools/perf/util/bpf_skel/dummy.bpf.c
> 
> --
> 2.24.1

-- 

- Arnaldo