linux-kernel - Re: [tip:perf/core] perf: Ignore non-sampling overflows

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Date:	Fri, 26 Nov 2010 20:20:29 +0100
From:	Francis Moreau <francis.moro@...il.com>
To:	mingo@...hat.com
Cc:	hpa@...or.com, linux-kernel@...r.kernel.org,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf: Ignore non-sampling overflows

Peter,

tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl> writes:
>
> perf: Ignore non-sampling overflows
>
> Some arch implementations call perf_event_overflow() by 'accident',
> ignore this.
>
> Reported-by: Francis Moreau <francis.moro@...il.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> LKML-Reference: <new-submission>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  kernel/perf_event.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index 98c5549..af1e63f 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -4240,6 +4240,13 @@ static int __perf_event_overflow(struct perf_event *event, int nmi,
>  	struct hw_perf_event *hwc = &event->hw;
>  	int ret = 0;
>  
> +	/*
> +	 * Non-sampling counters might still use the PMI to fold short
> +	 * hardware counters, ignore those.
> +	 */
> +	if (unlikely(!is_sampling_event(event)))
> +		return 0;
> +
>  	if (!throttle) {
>  		hwc->interrupts++;
>  	} else {

Couldn't we place this in perf_event_overflow() instead, like the
following ?

--8<---------------cut here---------------start------------->8---

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index df27fd8..1dabb54 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4267,7 +4267,9 @@ int perf_event_overflow(struct perf_event *event,
int nmi,
                  struct perf_sample_data *data,
                                            struct pt_regs *regs)
 {
-       return __perf_event_overflow(event, nmi, 1, data, regs);
+       if (is_sampling_event(event))
+          return __perf_event_overflow(event, nmi, 1, data, regs);
+          return 0;
 }
 
 /*

--8<---------------cut here---------------end--------------->8---

thanks,
-- 
Francis
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