linux-kernel - Re: [PATCH v2 6/8] perf header: Parse non-cpu pmu capabilities

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Date:   Mon, 16 May 2022 19:16:59 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     peterz@...radead.org, rrichter@....com, mingo@...hat.com,
        mark.rutland@....com, jolsa@...nel.org, namhyung@...nel.org,
        tglx@...utronix.de, bp@...en8.de, irogers@...gle.com,
        yao.jin@...ux.intel.com, james.clark@....com, leo.yan@...aro.org,
        kan.liang@...ux.intel.com, ak@...ux.intel.com, eranian@...gle.com,
        like.xu.linux@...il.com, x86@...nel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        sandipan.das@....com, ananth.narayan@....com, kim.phillips@....com,
        santosh.shukla@....com, Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v2 6/8] perf header: Parse non-cpu pmu capabilities


On 16-May-22 6:58 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, May 09, 2022 at 10:19:12AM +0530, Ravi Bangoria escreveu:
>> Pmus advertise their capabilities via sysfs attribute files but
>> perf tool currently parses only core(cpu) pmu capabilities. Add
>> support for parsing non-cpu pmu capabilities.
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
>> ---
>>  .../Documentation/perf.data-file-format.txt   |  18 ++
>>  tools/perf/util/env.c                         |  48 +++-
>>  tools/perf/util/env.h                         |  11 +
>>  tools/perf/util/header.c                      | 211 ++++++++++++++++++
>>  tools/perf/util/header.h                      |   1 +
>>  tools/perf/util/pmu.c                         |  15 +-
>>  tools/perf/util/pmu.h                         |   2 +
>>  7 files changed, 301 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
>> index f56d0e0fbff6..dea3acb36558 100644
>> --- a/tools/perf/Documentation/perf.data-file-format.txt
>> +++ b/tools/perf/Documentation/perf.data-file-format.txt
>> @@ -435,6 +435,24 @@ struct {
>>  	} [nr_pmu];
>>  };
>>  
>> +	HEADER_PMU_CAPS = 32,
>> +
>> +	List of pmu capabilities (except cpu pmu which is already
>> +	covered by HEADER_CPU_PMU_CAPS)
>> +
>> +struct {
>> +	u32 nr_pmus;
>> +	struct {
>> +		u8 core_type;	/* For hybrid topology */
> 
> Humm, I'd say use u32 here and..
> 
>> +		char pmu_name[];
>> +		u16 nr_caps;
> 
> Here, no need to save space here, I guess.

Yeah I know it's not a biggie but fwiw I thoughtfully allocated space.
256 types should be more than enough for core_type. Similarly no real
pmu will have more than 65,536 capabilities :)

Anyway, will convert them to u32.

Thanks,
Ravi