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Message-ID: <95506174-546c-9bf7-82af-09058550be6d@arm.com>
Date: Tue, 11 Jul 2023 15:04:54 +0100
From: James Clark <james.clark@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Will Deacon <will@...nel.org>,
Kan Liang <kan.liang@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-perf-users@...r.kernel.org, irogers@...gle.com
Subject: Re: [PATCH 3/4] arm_pmu: Remove unused
PERF_PMU_CAP_HETEROGENEOUS_CPUS capability
On 11/07/2023 13:08, Anshuman Khandual wrote:
>
>
> On 7/10/23 17:51, James Clark wrote:
>> Since commit bd2756811766 ("perf: Rewrite core context handling") the
>> relationship between perf_event_context and PMUs has changed so that
>> the error scenario that PERF_PMU_CAP_HETEROGENEOUS_CPUS originally
>> silenced no longer exists.
>>
>> Remove the capability and associated comment to avoid confusion that it
>> actually influences any perf core behavior. This change should be a
>> no-op.
>>
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>> drivers/perf/arm_pmu.c | 7 ++-----
>> 1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
>> index d8844a9461a2..297906df6628 100644
>> --- a/drivers/perf/arm_pmu.c
>> +++ b/drivers/perf/arm_pmu.c
>> @@ -872,15 +872,12 @@ struct arm_pmu *armpmu_alloc(void)
>> .attr_groups = pmu->attr_groups,
>> /*
>> * This is a CPU PMU potentially in a heterogeneous
>> - * 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).
>> - *
>> + * configuration (e.g. big.LITTLE) so
>> * PERF_PMU_CAP_EXTENDED_HW_TYPE is required to open the legacy
>> * 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_EXTENDED_REGS |
>> PERF_PMU_CAP_EXTENDED_HW_TYPE,
>
> Small nit, the second line could be folded back into the first one.
.clang-format has a column limit of 80 which is why it gets folded. The
kernel coding style guide also still says 80 is a strongly preferred
limit so I'll probably leave it.
>
>> };
>>
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