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

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Date:   Wed, 1 Jun 2022 09:55:31 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ravi Bangoria <ravi.bangoria@....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
Subject: Re: [PATCH v5 2/8] perf tool: Parse pmu caps sysfs only once



On 6/1/2022 9:51 AM, Ravi Bangoria wrote:
> 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.
> 

Ah, I see. Then the patch looks good to me.

Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Thanks,
Kan