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

[John Garry]

On 04/01/2023 05:05, Jing Zhang wrote:
> 在 2023/1/3 下午7:52, John Garry 写道:
> > On 03/01/2023 11:39, Jing Zhang wrote:
> > > The formula of topdown L1 on neoverse-n2 is from ARM sbsa7.0 platform
> > > design document [0], D37-38.
> >
> > I think that I mentioned this before - if the these metrics are coming from an sbsa doc, then they are standard. As such, we can make them "arch std events" and put them in a common json such as sbsa.json, so that other cores may reuse.
> >
> > You don't strictly have to do do this now, but it would be better.
>
> Hi John,

Hi Jing,

> I would really like to do this, but as discussed earlier, slot is different on each architectures.
> If I do not specify the value of the slot in sbsa.json, then in the json file of n2/v1, I need to
> overwrite each topdown "MetricExpr". In other words, the metrics placed in the sbsa.json file only
> reuse "BriefDescription", "MetricGroup" and "ScaleUnit". So I'm not sure if it's acceptable?

I don't see a lot of value in that really.

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?

> In addition, James mentioned that if the units and names and group names of different architectures
> are not unified, it will become complicated.

Thanks,
John