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Commit 4defea85 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf, x86: Prefer fixed-purpose counters when scheduling 



This avoids a scheduling failure for cases like:

  cycles, cycles, instructions, instructions (on Core2)

Which would end up being programmed like:

  PMC0, PMC1, FP-instructions, fail

Because all events will have the same weight.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-8tnwb92asqj7xajqqoty4gel@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bc1738f6

arch/x86/kernel/cpu/perf_event.c

+14 −5
Original line number Diff line number Diff line
@@ -574,17 +574,26 @@ static bool __perf_sched_find_counter(struct perf_sched *sched) 


	c = sched->constraints[sched->state.event];



	/* Prefer fixed purpose counters */

	if (x86_pmu.num_counters_fixed) {

		idx = X86_PMC_IDX_FIXED;

		for_each_set_bit_cont(idx, c->idxmsk, X86_PMC_IDX_MAX) {

			if (!__test_and_set_bit(idx, sched->state.used))

				goto done;

		}

	}

	/* Grab the first unused counter starting with idx */

	idx = sched->state.counter;

	for_each_set_bit_cont(idx, c->idxmsk, X86_PMC_IDX_MAX) {

	for_each_set_bit_cont(idx, c->idxmsk, X86_PMC_IDX_FIXED) {

		if (!__test_and_set_bit(idx, sched->state.used))

			break;

			goto done;

	}

	sched->state.counter = idx;



	if (idx >= X86_PMC_IDX_MAX)

	return false;



done:

	sched->state.counter = idx;



	if (c->overlap)

		perf_sched_save_state(sched);