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Message-ID: <597f53e0-5a5b-75a1-4054-253630a941f2@arm.com>
Date: Tue, 11 Jul 2023 15:12:44 +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 1/4] arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability
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@...gle.com>
>> Signed-off-by: James Clark <james.clark@....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 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] =
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