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arm64: perf: Allow more than one cycle counter to be used

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Currently:
$ perf stat -e cycles:u -e cycles:k  true

 Performance counter stats for 'true':

          2,24,699      cycles:u
     <not counted>      cycles:k	(0.00%)

       0.000788087 seconds time elapsed

We can not count more than one cycle counter in one instance,because we
allow to map cycle counter into PMCCNTR_EL0 only. However, if I did not
miss anything then specification do not prohibit to use PMEVCNTR<n>_EL0
for cycle count as well.

Modify the code so that it still prefers to use PMCCNTR_EL0 for cycle
counter, however allow to use PMEVCNTR<n>_EL0 if PMCCNTR_EL0 is already
in use.

After this patch:

$ perf stat -e cycles:u -e cycles:k   true

 Performance counter stats for 'true':

          2,17,310      cycles:u
          7,40,009      cycles:k

       0.000764149 seconds time elapsed

Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Pratyush Anand 2017-07-01 12:03:35 +05:30 committed by Will Deacon
parent aae4e7a8bc
commit 1031a15929
1 changed files with 4 additions and 7 deletions
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11
arch/arm64/kernel/perf_event.c
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@ -846,17 +846,14 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
struct hw_perf_event *hwc = &event->hw;
unsigned long evtype = hwc->config_base & ARMV8_PMU_EVTYPE_EVENT;
/* Always place a cycle counter into the cycle counter. */
/* Always prefer to place a cycle counter into the cycle counter. */
if (evtype == ARMV8_PMUV3_PERFCTR_CPU_CYCLES) {
if (test_and_set_bit(ARMV8_IDX_CYCLE_COUNTER, cpuc->used_mask))
return -EAGAIN;
return ARMV8_IDX_CYCLE_COUNTER;
if (!test_and_set_bit(ARMV8_IDX_CYCLE_COUNTER, cpuc->used_mask))
return ARMV8_IDX_CYCLE_COUNTER;
}
/*
* For anything other than a cycle counter, try and use
* the events counters
* Otherwise use events counters
*/
for (idx = ARMV8_IDX_COUNTER0; idx < cpu_pmu->num_events; ++idx) {
if (!test_and_set_bit(idx, cpuc->used_mask))