linux-kernel - Re: [PATCH v2] perf vendor events arm64: Add AmpereOne metrics

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Date:   Wed, 30 Aug 2023 11:42:47 -0700 (PDT)
From:   Ilkka Koskinen <ilkka@...amperecomputing.com>
To:     James Clark <james.clark@....com>
cc:     Ilkka Koskinen <ilkka@...amperecomputing.com>,
        John Garry <john.g.garry@...cle.com>,
        Ian Rogers <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] perf vendor events arm64: Add AmpereOne metrics



Hi James,

On Tue, 29 Aug 2023, James Clark wrote:
>
>
> On 26/08/2023 20:23, Ilkka Koskinen wrote:
>> This patch adds AmpereOne metrics. The metrics also work around
>> the issue related to some of the events.
>>
>> Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
>> ---
>>  .../arch/arm64/ampere/ampereone/metrics.json  | 396 ++++++++++++++++++
>>  1 file changed, 396 insertions(+)
>>  create mode 100644 tools/perf/pmu-events/arch/arm64/ampere/ampereone/metrics.json
>>
>> diff --git a/tools/perf/pmu-events/arch/arm64/ampere/ampereone/metrics.json b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/metrics.json
>> new file mode 100644
>> index 000000000000..b623d8a9e3dc
>> --- /dev/null
>> +++ b/tools/perf/pmu-events/arch/arm64/ampere/ampereone/metrics.json
>> @@ -0,0 +1,396 @@
>
> [...]
>
>> +    {
>> +        "MetricExpr": "STALL_SLOT_BACKEND / (CPU_CYCLES * 4)",
>> +        "BriefDescription": "Fraction of slots backend bound",
>> +        "MetricGroup": "Default;TopDownL1",
>> +        "MetricName": "backend_bound",
>> +        "ScaleUnit": "100%"
>> +    },
>
> Hi Ilkaa,
>
> For these topdown metrics, as long as they are the same as the standard
> one you can remove anything that is duplicated. This might make it
> easier to make changes across all the topdown metrics in the future and
> have consistent descriptions across CPUs. For example this backend_bound
> one could look like this:
>
>    {
>        "ArchStdEvent": "backend_bound",
>    }

Nice, basically the same way as architectured events.

>
> This assumes that you have the slots sysfs file available, otherwise you
> could leave only the formula in.
>
> We also decided to make the units for the topdown metrics "percent of
> slots" as we thought more specificity in the units was clearer.

I'll take a look at those and update the patch accordingly.

Cheers, Ilkka

>
> Thanks
> James
>
>> +    {
>> +        "MetricExpr": "1 - (retired_fraction + slots_lost_misspeculation_fraction + backend_bound)",
>> +        "BriefDescription": "Fraction of slots frontend bound",
>> +        "MetricGroup": "Default;TopDownL1",
>> +        "MetricName": "frontend_bound",
>> +        "ScaleUnit": "100%"
>> +    },
>> +    {
>> +        "MetricExpr": "(OP_SPEC - OP_RETIRED) / (CPU_CYCLES * 4)",
>> +        "BriefDescription": "Fraction of slots lost due to misspeculation",
>> +        "MetricGroup": "Default;TopDownL1",
>> +        "MetricName": "slots_lost_misspeculation_fraction",
>> +        "ScaleUnit": "100%"
>> +    },
>> +    {
>> +        "MetricExpr": "OP_RETIRED / (CPU_CYCLES * 4)",
>> +        "BriefDescription": "Fraction of slots retiring, useful work",
>> +        "MetricGroup": "Default;TopDownL1",
>> +        "MetricName": "retired_fraction",
>> +        "ScaleUnit": "100%"
>> +    },
>> +    {
>