| Message ID | 20240906191539.4847-1-ilkka@os.amperecomputing.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] perf: arm_pmuv3: Use BR_RETIRED for HW branch event if enabled | expand |
On Fri, 06 Sep 2024 12:15:39 -0700, Ilkka Koskinen wrote: > The PMU driver attempts to use PC_WRITE_RETIRED for the HW branch event, > if enabled. However, PC_WRITE_RETIRED counts only taken branches, > whereas BR_RETIRED counts also non-taken ones. > > Furthermore, perf uses HW branch event to calculate branch misses ratio, > implying BR_RETIRED is the correct event to count. > > [...] Applied to will (for-next/perf), thanks! [1/1] perf: arm_pmuv3: Use BR_RETIRED for HW branch event if enabled https://git.kernel.org/will/c/5967a19f1c2f Cheers,
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c index d246840797b6..f5ee6e2adb30 100644 --- a/drivers/perf/arm_pmuv3.c +++ b/drivers/perf/arm_pmuv3.c @@ -1089,14 +1089,14 @@ static int __armv8_pmuv3_map_event_id(struct arm_pmu *armpmu, 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; + if (test_bit(ARMV8_PMUV3_PERFCTR_PC_WRITE_RETIRED, + armpmu->pmceid_bitmap)) + return ARMV8_PMUV3_PERFCTR_PC_WRITE_RETIRED; + return HW_OP_UNSUPPORTED; }
The PMU driver attempts to use PC_WRITE_RETIRED for the HW branch event, if enabled. However, PC_WRITE_RETIRED counts only taken branches, whereas BR_RETIRED counts also non-taken ones. Furthermore, perf uses HW branch event to calculate branch misses ratio, implying BR_RETIRED is the correct event to count. We keep PC_WRITE_RETIRED still as an option in case BR_RETIRED isn't implemented. Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com> --- v2: Instead of removing PC_WRITE_RETIRED, keep it as an alternative --- drivers/perf/arm_pmuv3.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)