Messages in this thread Patch in this message | | | Date | Mon, 27 Mar 2023 14:25:27 +0200 | Subject | [PATCH v4] arm64: pmuv3: dynamically map PERF_COUNT_HW_BRANCH_INSTRUCTIONS | From | Peter Newman <> |
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From: Stephane Eranian <eranian@google.com>
The mapping of perf_events generic hardware events to actual PMU events on ARM PMUv3 may not always be correct. This is in particular true for the PERF_COUNT_HW_BRANCH_INSTRUCTIONS event. Although the mapping points to an architected event, it may not always be available. This can be seen with a simple:
$ perf stat -e branches sleep 0 Performance counter stats for 'sleep 0':
<not supported> branches
0.001401081 seconds time elapsed
Yet the hardware does have an event that could be used for branches.
Dynamically check for a supported hardware event which can be used for PERF_COUNT_HW_BRANCH_INSTRUCTIONS at mapping time.
And with that:
$ perf stat -e branches sleep 0
Performance counter stats for 'sleep 0':
166,739 branches
0.000832163 seconds time elapsed
Based-on: https://lore.kernel.org/all/YvunKCJHSXKz%2FkZB@FVFF77S0Q05N Based-on-patch-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Newman <peternewman@google.com> --- v3->v4: - splice Mark's patch with Stephane's problem statement v2->v3: - removed prints per Will's suggestion [v3] https://lore.kernel.org/all/20220816130221.885920-1-peternewman@google.com/ [v2] https://lore.kernel.org/lkml/20220324181458.3216262-1-eranian@google.com/
arch/arm64/kernel/perf_event.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index dde06c0f97f3..ee63f8e719ea 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -45,7 +45,6 @@ static const unsigned armv8_pmuv3_perf_map[PERF_COUNT_HW_MAX] = { [PERF_COUNT_HW_INSTRUCTIONS] = ARMV8_PMUV3_PERFCTR_INST_RETIRED, [PERF_COUNT_HW_CACHE_REFERENCES] = ARMV8_PMUV3_PERFCTR_L1D_CACHE, [PERF_COUNT_HW_CACHE_MISSES] = ARMV8_PMUV3_PERFCTR_L1D_CACHE_REFILL, - [PERF_COUNT_HW_BRANCH_INSTRUCTIONS] = ARMV8_PMUV3_PERFCTR_PC_WRITE_RETIRED, [PERF_COUNT_HW_BRANCH_MISSES] = ARMV8_PMUV3_PERFCTR_BR_MIS_PRED, [PERF_COUNT_HW_BUS_CYCLES] = ARMV8_PMUV3_PERFCTR_BUS_CYCLES, [PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] = ARMV8_PMUV3_PERFCTR_STALL_FRONTEND, @@ -1048,6 +1047,28 @@ static void armv8pmu_reset(void *info) armv8pmu_pmcr_write(pmcr); } +static int __armv8_pmuv3_map_event_id(struct arm_pmu *armpmu, + struct perf_event *event) +{ + if (event->attr.type == PERF_TYPE_HARDWARE && + event->attr.config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) { + + if (test_bit(ARMV8_PMUV3_PERFCTR_PC_WRITE_RETIRED, + armpmu->pmceid_bitmap)) + return ARMV8_PMUV3_PERFCTR_PC_WRITE_RETIRED; + + if (test_bit(ARMV8_PMUV3_PERFCTR_BR_RETIRED, + armpmu->pmceid_bitmap)) + return ARMV8_PMUV3_PERFCTR_BR_RETIRED; + + return HW_OP_UNSUPPORTED; + } + + return armpmu_map_event(event, &armv8_pmuv3_perf_map, + &armv8_pmuv3_perf_cache_map, + ARMV8_PMU_EVTYPE_EVENT); +} + static int __armv8_pmuv3_map_event(struct perf_event *event, const unsigned (*extra_event_map) [PERF_COUNT_HW_MAX], @@ -1059,9 +1080,7 @@ static int __armv8_pmuv3_map_event(struct perf_event *event, int hw_event_id; struct arm_pmu *armpmu = to_arm_pmu(event->pmu); - hw_event_id = armpmu_map_event(event, &armv8_pmuv3_perf_map, - &armv8_pmuv3_perf_cache_map, - ARMV8_PMU_EVTYPE_EVENT); + hw_event_id = __armv8_pmuv3_map_event_id(armpmu, event); /* * CHAIN events only work when paired with an adjacent counter, and it -- 2.40.0.348.gf938b09366-goog
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