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perf_counter: Do not throttle single swcounter events

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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: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-09-17 18:47:11 +02:00 committed by Ingo Molnar
parent 0ec04e16d0
commit 850bc73ffc
1 changed files with 13 additions and 4 deletions
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17
kernel/perf_counter.c
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@ -3494,14 +3494,15 @@ static void perf_log_throttle(struct perf_counter *counter, int enable)
* Generic counter overflow handling, sampling.
*/
int perf_counter_overflow(struct perf_counter *counter, int nmi,
struct perf_sample_data *data)
static int __perf_counter_overflow(struct perf_counter *counter, int nmi,
int throttle, struct perf_sample_data *data)
{
int events = atomic_read(&counter->event_limit);
int throttle = counter->pmu->unthrottle != NULL;
struct hw_perf_counter *hwc = &counter->hw;
int ret = 0;
throttle = (throttle && counter->pmu->unthrottle != NULL);
if (!throttle) {
hwc->interrupts++;
} else {
@ -3554,6 +3555,12 @@ int perf_counter_overflow(struct perf_counter *counter, int nmi,
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
*/
@ -3592,6 +3599,7 @@ static void perf_swcounter_overflow(struct perf_counter *counter,
int nmi, struct perf_sample_data *data)
{
struct hw_perf_counter *hwc = &counter->hw;
int throttle = 0;
u64 overflow;
data->period = counter->hw.last_period;
@ -3601,13 +3609,14 @@ static void perf_swcounter_overflow(struct perf_counter *counter,
return;
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
* hwc->interrupts == MAX_INTERRUPTS.
*/
break;
}
throttle = 0;
}
}