linux-kernel - Re: [PATCH 3/5] perf/core: Account dropped samples from BPF

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Message-ID: <CAP045Arcn_zrQvzv+4ihCXOPgcsuMVe_VdgR-cny63POaT5g-w@mail.gmail.com>
Date: Wed, 4 Sep 2024 21:17:21 -0700
From: Kyle Huey <me@...ehuey.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	Kan Liang <kan.liang@...ux.intel.com>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Stephane Eranian <eranian@...gle.com>, Ravi Bangoria <ravi.bangoria@....com>, 
	Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, Song Liu <song@...nel.org>, 
	bpf@...r.kernel.org
Subject: Re: [PATCH 3/5] perf/core: Account dropped samples from BPF

On Wed, Sep 4, 2024 at 8:10 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Like in the software events, the BPF overflow handler can drop samples
> by returning 0.  Let's count the dropped samples here too.
>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Andrii Nakryiko <andrii@...nel.org>
> Cc: Song Liu <song@...nel.org>
> Cc: Kyle Huey <me@...ehuey.com>
> Cc: bpf@...r.kernel.org
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  kernel/events/core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 8250e76f63358689..ba1f6b51ea26db5b 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9808,8 +9808,10 @@ static int __perf_event_overflow(struct perf_event *event,
>
>         ret = __perf_event_account_interrupt(event, throttle);
>
> -       if (event->prog && !bpf_overflow_handler(event, data, regs))
> +       if (event->prog && !bpf_overflow_handler(event, data, regs)) {
> +               atomic64_inc(&event->dropped_samples);
>                 return ret;
> +       }
>
>         /*
>          * XXX event_limit might not quite work as expected on inherited
> --
> 2.46.0.469.g59c65b2a67-goog
>

lgtm

- Kyle