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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-8tnwb92asqj7xajqqoty4gel@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index fa6fdec..66f8ba9 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -574,16 +574,25 @@
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;
+ return false;
+
+done:
+ sched->state.counter = idx;
if (c->overlap)
perf_sched_save_state(sched);
