Messages in this thread | | | Date | Mon, 3 Apr 2023 08:24:13 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v4] arm64: pmuv3: dynamically map PERF_COUNT_HW_BRANCH_INSTRUCTIONS |
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On Mon, Mar 27, 2023 at 02:25:27PM +0200, Peter Newman wrote: > 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>
Thanks for reworking the patch; the patch itself and commit message look good to me.
I'd like to keep my S-o-b here for the code itself; could we please make the tags:
Co-Developed-by: Stephane Eranian <eranian@google.com> Signed-off-by: Stephane Eranian <eranian@google.com> Co-Developed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Co-Developed-by: Peter Newman <peternewman@google.com> Signed-off-by: Peter Newman <peternewman@google.com> Link: https://lore.kernel.org/all/YvunKCJHSXKz%2FkZB@FVFF77S0Q05N
That follow the conventions documented in:
https://www.kernel.org/doc/html/latest/process/submitting-patches.html
Thanks, Mark.
> --- > 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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