From 1031a1592908ccd3240f4a5731c96c382c932310 Mon Sep 17 00:00:00 2001 From: Pratyush Anand Date: Sat, 1 Jul 2017 12:03:35 +0530 Subject: [PATCH] arm64: perf: Allow more than one cycle counter to be used Currently: $ perf stat -e cycles:u -e cycles:k true Performance counter stats for 'true': 2,24,699 cycles:u 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_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_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 Signed-off-by: Will Deacon --- arch/arm64/kernel/perf_event.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index b5798ba21189..372317667773 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -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)) -- 2.11.0