linux-kernel - Re: [PATCH 1/2] perf/x86/amd/core: Update stalled-cycles-* events for Zen 2 and later

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Date: Tue, 26 Mar 2024 11:32:38 +0530
From: Sandipan Das <sandipan.das@....com>
To: Ian Rogers <irogers@...gle.com>, mingo@...nel.org
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 x86@...nel.org, peterz@...radead.org, acme@...nel.org, namhyung@...nel.org,
 mark.rutland@....com, alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
 adrian.hunter@...el.com, tglx@...utronix.de, bp@...en8.de,
 eranian@...gle.com, ravi.bangoria@....com, ananth.narayan@....com
Subject: Re: [PATCH 1/2] perf/x86/amd/core: Update stalled-cycles-* events for
 Zen 2 and later

On 3/25/2024 8:04 PM, Ian Rogers wrote:
> On Mon, Mar 25, 2024 at 12:48 AM Sandipan Das <sandipan.das@....com> wrote:
>>
>> AMD processors based on Zen 2 and later microarchitectures do not
>> support PMCx087 (instruction pipe stalls) which is used as the backing
>> event for "stalled-cycles-frontend" and "stalled-cycles-backend". Use
>> PMCx0A9 (cycles where micro-op queue is empty) instead to count frontend
>> stalls and remove the entry for backend stalls since there is no direct
>> replacement.
>>
>> Signed-off-by: Sandipan Das <sandipan.das@....com>
> 
> This looks good to me. Should there be a Fixes tag for the sake of backports?
> 

My bad. Yes, there should a fixes tag.

Fixes: 3fe3331bb285 ("perf/x86/amd: Add event map for AMD Family 17h")

Ingo, I see that you have already pushed this to the perf/urgent branch.
Should I send a v2?

> Reviewed-by: Ian Rogers <irogers@...gle.com>
> 
> Thanks,
> Ian
> 
>> ---
>>  arch/x86/events/amd/core.c | 20 +++++++++++++++++---
>>  1 file changed, 17 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
>> index aec16e581f5b..afe4a809f2ed 100644
>> --- a/arch/x86/events/amd/core.c
>> +++ b/arch/x86/events/amd/core.c
>> @@ -250,7 +250,7 @@ static const u64 amd_perfmon_event_map[PERF_COUNT_HW_MAX] =
>>  /*
>>   * AMD Performance Monitor Family 17h and later:
>>   */
>> -static const u64 amd_f17h_perfmon_event_map[PERF_COUNT_HW_MAX] =
>> +static const u64 amd_zen1_perfmon_event_map[PERF_COUNT_HW_MAX] =
>>  {
>>         [PERF_COUNT_HW_CPU_CYCLES]              = 0x0076,
>>         [PERF_COUNT_HW_INSTRUCTIONS]            = 0x00c0,
>> @@ -262,10 +262,24 @@ static const u64 amd_f17h_perfmon_event_map[PERF_COUNT_HW_MAX] =
>>         [PERF_COUNT_HW_STALLED_CYCLES_BACKEND]  = 0x0187,
>>  };
>>
>> +static const u64 amd_zen2_perfmon_event_map[PERF_COUNT_HW_MAX] =
>> +{
>> +       [PERF_COUNT_HW_CPU_CYCLES]              = 0x0076,
>> +       [PERF_COUNT_HW_INSTRUCTIONS]            = 0x00c0,
>> +       [PERF_COUNT_HW_CACHE_REFERENCES]        = 0xff60,
>> +       [PERF_COUNT_HW_CACHE_MISSES]            = 0x0964,
>> +       [PERF_COUNT_HW_BRANCH_INSTRUCTIONS]     = 0x00c2,
>> +       [PERF_COUNT_HW_BRANCH_MISSES]           = 0x00c3,
>> +       [PERF_COUNT_HW_STALLED_CYCLES_FRONTEND] = 0x00a9,
>> +};
>> +
>>  static u64 amd_pmu_event_map(int hw_event)
>>  {
>> -       if (boot_cpu_data.x86 >= 0x17)
>> -               return amd_f17h_perfmon_event_map[hw_event];
>> +       if (cpu_feature_enabled(X86_FEATURE_ZEN2) || boot_cpu_data.x86 >= 0x19)
>> +               return amd_zen2_perfmon_event_map[hw_event];
>> +
>> +       if (cpu_feature_enabled(X86_FEATURE_ZEN1))
>> +               return amd_zen1_perfmon_event_map[hw_event];
>>
>>         return amd_perfmon_event_map[hw_event];
>>  }
>> --
>> 2.34.1
>>