linux-kernel - Re: [PATCH v5 2/8] perf tool: Parse pmu caps sysfs only once

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Date:   Wed, 1 Jun 2022 19:21:58 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, irogers@...gle.com,
        peterz@...radead.org, rrichter@....com, mingo@...hat.com,
        mark.rutland@....com, namhyung@...nel.org, tglx@...utronix.de,
        bp@...en8.de, james.clark@....com, leo.yan@...aro.org,
        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 v5 2/8] perf tool: Parse pmu caps sysfs only once

Hi Kan,

[...]

>> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
>> index 541889fa9f9c..4b45fd8da5a3 100644
>> --- a/tools/perf/util/pmu.h
>> +++ b/tools/perf/util/pmu.h
>> @@ -46,6 +46,8 @@ struct perf_pmu {
>>       struct perf_cpu_map *cpus;
>>       struct list_head format;  /* HEAD struct perf_pmu_format -> list */
>>       struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
>> +    bool caps_initialized;
>> +    u32 nr_caps;
> 
> If they are just used for the cache purpose, I don't think we need to add the variables in the struct perf_pmu.
> 
> A static variable should be good enough. See sysctl__nmi_watchdog_enabled().

These fields are per pmu. Static variable won't help :) And they are
used in subsequent patches as well.

Thanks,
Ravi