On 2015/10/12 20:02, Peter Zijlstra wrote:
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); elseTry and guarantee sample_disable lives in the same cacheline as overflow_handler.
Could you please explain why we need them to be in a same cacheline? Thank you.
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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