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SubjectRe: [PATCH v2 1/4] arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability
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On 7/24/23 19:14, James Clark wrote:
> This capability gives us the ability to open PERF_TYPE_HARDWARE and
> PERF_TYPE_HW_CACHE events on a specific PMU for free. All the
> implementation is contained in the Perf core and tool code so no change
> to the Arm PMU driver is needed.
>
> The following basic use case now results in Perf opening the event on
> all PMUs rather than picking only one in an unpredictable way:
>
> $ perf stat -e cycles -- taskset --cpu-list 0,1 stress -c 2
>
> Performance counter stats for 'taskset --cpu-list 0,1 stress -c 2':
>
> 963279620 armv8_cortex_a57/cycles/ (99.19%)
> 752745657 armv8_cortex_a53/cycles/ (94.80%)
>
> Fixes: 55bcf6ef314a ("perf: Extend PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE")
> Suggested-by: Ian Rogers <irogers@google.com>
> Acked-by: Ian Rogers <irogers@google.com>
> Signed-off-by: James Clark <james.clark@arm.com>

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

> ---
> drivers/perf/arm_pmu.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index f6ccb2cd4dfc..2e79201daa4a 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -880,8 +880,13 @@ struct arm_pmu *armpmu_alloc(void)
> * configuration (e.g. big.LITTLE). This is not an uncore PMU,
> * and we have taken ctx sharing into account (e.g. with our
> * pmu::filter callback and pmu::event_init group validation).
> + *
> + * PERF_PMU_CAP_EXTENDED_HW_TYPE is required to open
> + * PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE events on a
> + * specific PMU.
> */
> - .capabilities = PERF_PMU_CAP_HETEROGENEOUS_CPUS | PERF_PMU_CAP_EXTENDED_REGS,
> + .capabilities = PERF_PMU_CAP_HETEROGENEOUS_CPUS | PERF_PMU_CAP_EXTENDED_REGS |
> + PERF_PMU_CAP_EXTENDED_HW_TYPE,
> };
>
> pmu->attr_groups[ARMPMU_ATTR_GROUP_COMMON] =

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