linux-kernel - Re: [PATCH v7 3/3] perf-stat: enable counting events for BPF programs

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Date:   Tue, 12 Jan 2021 16:35:14 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, kernel-team@...com
Subject: Re: [PATCH v7 3/3] perf-stat: enable counting events for BPF programs

Hi,

On Wed, Dec 30, 2020 at 6:42 AM Song Liu <songliubraving@...com> wrote:
>
> Introduce perf-stat -b option, which counts events for BPF programs, like:
>
> [root@...alhost ~]# ~/perf stat -e ref-cycles,cycles -b 254 -I 1000
>      1.487903822            115,200      ref-cycles
>      1.487903822             86,012      cycles
>      2.489147029             80,560      ref-cycles
>      2.489147029             73,784      cycles
>      3.490341825             60,720      ref-cycles
>      3.490341825             37,797      cycles
>      4.491540887             37,120      ref-cycles
>      4.491540887             31,963      cycles
>
> The example above counts cycles and ref-cycles of BPF program of id 254.
> This is similar to bpftool-prog-profile command, but more flexible.
>
> perf-stat -b creates per-cpu perf_event and loads fentry/fexit BPF
> programs (monitor-progs) to the target BPF program (target-prog). The
> monitor-progs read perf_event before and after the target-prog, and
> aggregate the difference in a BPF map. Then the user space reads data
> from these maps.
>
> A new struct bpf_counter is introduced to provide common interface that
> uses BPF programs/maps to count perf events.

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung