Re: [PATCH 1/4] arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability

[Ian Rogers]

On Tue, Jul 11, 2023 at 7:12 AM James Clark <james.clark@xxxxxxx> wrote:
>
>
>
> On 11/07/2023 13:01, Anshuman Khandual wrote:
> >
> >
> > On 7/10/23 17:51, 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@xxxxxxxxxx>
> >> Signed-off-by: James Clark <james.clark@xxxxxxx>

Hi ARM Linux and ARM Linux PMU people,

Could this patch be picked up for Linux 6.5? I don't see it in the
tree and it seems a shame to have to wait for it. The other patches do
cleanup and so waiting for 6.6 seems okay.

Thanks,
Ian

> >> ---
> >>  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 277e29fbd504..d8844a9461a2 100644
> >> --- a/drivers/perf/arm_pmu.c
> >> +++ b/drivers/perf/arm_pmu.c
> >> @@ -875,8 +875,13 @@ 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 the legacy
> >
> > s/legacy/generic ? These hardware events are still around.
>
> True, I thought I saw it mentioned that way somewhere, but I can
> probably just remove it altogether. PERF_TYPE_HARDWARE and
> PERF_TYPE_HW_CACHE is enough.
>
>
> >
> >> +             * 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] =