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

[Ilkka Koskinen]

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@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> >  .../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%"
> > +    },
> > +    {