On 26.11.10 10:04:56, tip-bot for Peter Zijlstra wrote:
> Commit-ID: 963988262c3c8f4234f64a0dde59446a295e07bb
> Gitweb: http://git.kernel.org/tip/963988262c3c8f4234f64a0dde59446a295e07bb
> Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> AuthorDate: Wed, 24 Nov 2010 18:55:29 +0100
> Committer: Ingo Molnar <mingo@xxxxxxx>
> CommitDate: Fri, 26 Nov 2010 15:14:55 +0100
>
> perf: Ignore non-sampling overflows
>
> Some arch implementations call perf_event_overflow() by 'accident',
> ignore this.
>
> Reported-by: Francis Moreau <francis.moro@xxxxxxxxx>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> LKML-Reference: <new-submission>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> ---
> 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;
> +
Peter,
do you remember the background of this change. This check silently
drops data of non-sampling events. I want to use perf_event_overflow()
to write to the buffer and want to modify the check, but don't see
which 'accidentally' interrupts may occur that must be ignored.
I was thinking of modifying the check to something like:
static inline bool is_sampling_event(struct perf_event *event)
{
return event->attr.sample_type != 0;
}
or
if (unlikely(!is_sampling_event(event) && !event->attr.sample_type))
...
Thanks,
-Robert
> if (!throttle) {
> hwc->interrupts++;
> } else {
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