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Commit 6a24ed6c authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Fix frequency adjustment for < HZ 



Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 689802b2

include/linux/perf_counter.h

+3 −0
Original line number Diff line number Diff line
@@ -373,6 +373,9 @@ struct hw_perf_counter { 
	u64				sample_period;

	atomic64_t			period_left;

	u64				interrupts;



	u64				freq_count;

	u64				freq_interrupts;

#endif

};

kernel/perf_counter.c

+25 −7
Original line number Diff line number Diff line
@@ -1187,8 +1187,9 @@ static void perf_log_period(struct perf_counter *counter, u64 period); 
static void perf_adjust_freq(struct perf_counter_context *ctx)

{

	struct perf_counter *counter;

	struct hw_perf_counter *hwc;

	u64 interrupts, sample_period;

	u64 events, period;

	u64 events, period, freq;

	s64 delta;



	spin_lock(&ctx->lock);
@@ -1196,8 +1197,10 @@ static void perf_adjust_freq(struct perf_counter_context *ctx) 
		if (counter->state != PERF_COUNTER_STATE_ACTIVE)

			continue;



		interrupts = counter->hw.interrupts;

		counter->hw.interrupts = 0;

		hwc = &counter->hw;



		interrupts = hwc->interrupts;

		hwc->interrupts = 0;



		if (interrupts == MAX_INTERRUPTS) {

			perf_log_throttle(counter, 1);
@@ -1208,20 +1211,35 @@ static void perf_adjust_freq(struct perf_counter_context *ctx) 
		if (!counter->attr.freq || !counter->attr.sample_freq)

			continue;



		events = HZ * interrupts * counter->hw.sample_period;

		if (counter->attr.sample_freq < HZ) {

			freq = counter->attr.sample_freq;



			hwc->freq_count += freq;

			hwc->freq_interrupts += interrupts;



			if (hwc->freq_count < HZ)

				continue;



			interrupts = hwc->freq_interrupts;

			hwc->freq_interrupts = 0;

			hwc->freq_count -= HZ;

		} else

			freq = HZ;



		events = freq * interrupts * hwc->sample_period;

		period = div64_u64(events, counter->attr.sample_freq);



		delta = (s64)(1 + period - counter->hw.sample_period);

		delta = (s64)(1 + period - hwc->sample_period);

		delta >>= 1;



		sample_period = counter->hw.sample_period + delta;

		sample_period = hwc->sample_period + delta;



		if (!sample_period)

			sample_period = 1;



		perf_log_period(counter, sample_period);



		counter->hw.sample_period = sample_period;

		hwc->sample_period = sample_period;

	}

	spin_unlock(&ctx->lock);

}