On Mon, Oct 12, 2015 at 09:02:42AM +0000, Kaixu Xia wrote:
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -483,6 +483,8 @@ struct perf_event {
> perf_overflow_handler_t overflow_handler;
> void *overflow_handler_context;
>
> + atomic_t *sample_disable;
> +
> #ifdef CONFIG_EVENT_TRACING
> struct trace_event_call *tp_event;
> struct event_filter *filter;
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index b11756f..f6ef45c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6337,6 +6337,9 @@ static int __perf_event_overflow(struct perf_event
> *event,
> irq_work_queue(&event->pending);
> }
>
> + if ((event->sample_disable) && atomic_read(event->sample_disable))
> + return ret;
> +
> if (event->overflow_handler)
> event->overflow_handler(event, data, regs);
> else
Try and guarantee sample_disable lives in the same cacheline as
overflow_handler.
I think we should at the very least replace the kzalloc() currently used
with a cacheline aligned alloc, and check the structure layout to verify
these two do in fact share a cacheline.
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