linux-kernel - Re: [PATCH v2 2/2] perf test: Add event group test

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Message-ID: <b47c4bc7-aed3-e1a0-c791-818af091d976@amd.com>
Date:   Thu, 1 Dec 2022 21:59:44 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     irogers@...gle.com, acme@...nel.org, jolsa@...hat.com,
        namhyung@...nel.org, peterz@...radead.org, mark.rutland@....com,
        adrian.hunter@...el.com, alexander.shishkin@...ux.intel.com,
        carsten.haitzler@....com, leo.yan@...aro.org, maddy@...ux.ibm.com,
        kjain@...ux.ibm.com, atrajeev@...ux.vnet.ibm.com,
        tmricht@...ux.ibm.com, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, sandipan.das@....com,
        ananth.narayan@....com, santosh.shukla@....com,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v2 2/2] perf test: Add event group test

On 01-Dec-22 9:17 PM, Liang, Kan wrote:
> 
> 
> On 2022-12-01 10:29 a.m., Ravi Bangoria wrote:
>>>>   /* Uncore pmus that support more than 3 counters */
>>>>   static struct uncore_pmus {
>>>>       char *name;
>>>>       unsigned long config;
>>>>   } uncore_pmus[] = {
>>>>       { "amd_l3",         0x0  },
>>>>       { "amd_df",         0x0  },
>>>>       { "uncore_imc_xxx", 0xff },   /* Intel */
>>>
>>> IMC seems a safe choice. AFAIK, we should have at least uncore_imc_0 for
>>> all the existing Intel platforms. { "uncore_imc_0", 0x1 }
>>
>> Ok. Ian said he don't see uncore_imc_0 on his tigerlake machine. Are you
>> sure uncore_imc_0 should be present on all existing Intel platforms?
> 
> For TGL and older client platforms, there is only free running IMC
> counters. For other uncore PMUs on the old client platforms, I cannot
> guarantee that then always have more then 2 counters. I think you can
> skip the uncore test for these old platforms if you need at least 3
> counters.
> 
> 
>>
>>>>       { "intel_xxx_pmu2", 0xff },   /* Intel */
>>>
>>> Intel doesn't have such uncore PMUs.
>>
>> Yeah this was just for example purpose.
>>
>>>>       { "abc_pmu1",       0x0  },   /* Arm */
>>>>       { "hv_24x7",        0xa  },   /* PowerPC */
>>>>       { ...                    },
>>>>   };
>>>>
>>>>   perf_pmus__for_each_pmu(pmu) {
>>>>       if (pmu present in uncore_pmus[])
>>>>           type[2] = pmu->type;
>>>>           config[2] = pmu->config;>   }
>>>
>>>
>>> Not sure the uncore_pmus[] can cover all possible names for all
>>> architectures.
>>
>> It doesn't need to cover _all_ possible names. It just needs to cover
>> minimal set of names which can cover all platforms for that architecture.
>>>> Maybe we should fall back to the first uncore PMU and try again if
>>> nothing match the uncore_pmus[].
>>
>> That's a good point. However, this can endup with the same problem you
>> mentioned: it may trigger false alarm on some platform. So better to
>> skip the test(and let someone add proper pmu in this list) rather than
>> proving false negative result?
> 
> OK. Skipping the test for this case sounds good to me.

Thanks. Will respin with this change.

Ravi