Re: [PATCH v5 1/6] perf vendor events arm64: Add topdown L1 metrics for neoverse-n2

[John Garry]

On 05/01/2023 10:05, Jing Zhang wrote:
> > However, for this value of slot, isn't this discoverable from a system register per core? Quoting the sbsa: "The IMPLEMENTATION DEFINED constant SLOTS is discoverable from the system register PMMIR_EL1.SLOTS." Did you consider how this could be used?
>
> This may be a feasible idea. The value of slots comes from the register PMMIR_EL1, which I can read in
> /sys/bus/event_source/device/armv8_pmuv3_*/caps/slots. But how do I replace the slots in MetricExpr with the
> read slots values? Currently I understand that parameters in metricExpr only support events and constants.

Maybe during runtime we could create a pseudo metric/event for SLOT. 
This metric would be created during init, and it always just returns the 
value which was read from PMMIR_EL1.

I'm not sure how well that would play will trying to resolve metrics 
when building generated pmu-events.c, but I don't think it's all too 
difficult to achieve.

Have you actually read this value for the n2 core? Does look correct?

Thanks,
John