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Commit 850bc73f authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Do not throttle single swcounter events 



We can have swcounter events that contribute more than a single
count per event, when used with a non-zero period, those can
generate multiple events, which is when we need throttling.

However, swcounter that contribute only a single count per event
can only come as fast as we can run code, hence don't throttle
them.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0ec04e16

kernel/perf_counter.c

+13 −4
Original line number Original line Diff line number Diff line
@@ -3494,14 +3494,15 @@ static void perf_log_throttle(struct perf_counter *counter, int enable) 
 * Generic counter overflow handling, sampling.

 * Generic counter overflow handling, sampling.

 */

 */





int perf_counter_overflow(struct perf_counter *counter, int nmi,

static int __perf_counter_overflow(struct perf_counter *counter, int nmi,

			  struct perf_sample_data *data)

				   int throttle, struct perf_sample_data *data)

{

{

	int events = atomic_read(&counter->event_limit);

	int events = atomic_read(&counter->event_limit);

	int throttle = counter->pmu->unthrottle != NULL;

	struct hw_perf_counter *hwc = &counter->hw;

	struct hw_perf_counter *hwc = &counter->hw;

	int ret = 0;

	int ret = 0;





	throttle = (throttle && counter->pmu->unthrottle != NULL);



	if (!throttle) {

	if (!throttle) {

		hwc->interrupts++;

		hwc->interrupts++;

	} else {

	} else {
@@ -3554,6 +3555,12 @@ int perf_counter_overflow(struct perf_counter *counter, int nmi, 
	return ret;

	return ret;

}

}





int perf_counter_overflow(struct perf_counter *counter, int nmi,

			  struct perf_sample_data *data)

{

	return __perf_counter_overflow(counter, nmi, 1, data);

}



/*

/*

 * Generic software counter infrastructure

 * Generic software counter infrastructure

 */

 */
@@ -3592,6 +3599,7 @@ static void perf_swcounter_overflow(struct perf_counter *counter, 
				    int nmi, struct perf_sample_data *data)

				    int nmi, struct perf_sample_data *data)

{

{

	struct hw_perf_counter *hwc = &counter->hw;

	struct hw_perf_counter *hwc = &counter->hw;

	int throttle = 0;

	u64 overflow;

	u64 overflow;





	data->period = counter->hw.last_period;

	data->period = counter->hw.last_period;
@@ -3601,13 +3609,14 @@ static void perf_swcounter_overflow(struct perf_counter *counter, 
		return;

		return;





	for (; overflow; overflow--) {

	for (; overflow; overflow--) {

		if (perf_counter_overflow(counter, nmi, data)) {

		if (__perf_counter_overflow(counter, nmi, throttle, data)) {

			/*

			/*

			 * We inhibit the overflow from happening when

			 * We inhibit the overflow from happening when

			 * hwc->interrupts == MAX_INTERRUPTS.

			 * hwc->interrupts == MAX_INTERRUPTS.

			 */

			 */

			break;

			break;

		}

		}

		throttle = 0;

	}

	}

}

}