Messages in this thread | | | Date | Thu, 27 Jan 2022 11:42:27 +0000 | Subject | Re: [RFC PATCH v2 0/5] topdown with metrics | From | Andrew Kilroy <> |
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On 20/01/2022 09:26, John Garry wrote: > On 11/01/2022 15:07, Andrew Kilroy wrote: >> This patch series adds the ability for the --topdown option to use >> metrics (defined in json files in the pmu-events directory) to describe >> how to calculate and determine the output columns for topdown level 1. >> >> For this to work, a number of metrics have to be defined for the >> relevant processor with the MetricGroup name "TopDownL1". perf will >> arrange for the events defined in each metric to be collected, and each >> metric will be displayed in the output, as if >> >> perf stat -M 'TopDownL1' --metric-only -- exampleapp >> >> had been used. >> >> Topdown was already implemented where certain kernel events are defined. >> If these kernel events are defined, the new json metrics behaviour is >> not used. The json metrics approach is only used if the kernel events >> are absent. >> >> The last patch in the series disables the json metrics behaviour on x86. >> This is because of concerns that due to SMT it's not straightforward to >> express the various formulas as json for certain x86 cpus. See > > I suppose this solution is ok. >
Thanks, would you mind giving it a Reviewed-By?
> A concern is that today we only have 1x arm64 platform which actually > supports this in mainline. > > Do you have any more which you plan to support? >
The Neoverse cores, mainly.
> I think that it's the frontend bound and fetch_bubble event which > doesn't have a standard arm solution. > > Note that I do have a series for perf tool which can read arm cpu pmu > sysfs events folder to find events which are implemented (I don't think > all required events are mandated) and match that against the common arch > events JSON, so that we don't need a JSON definition file for each core > implementation from all implementators - this would improve scalability. > However a concern is that some events - like inst_spec - have imp def > meaning, so may not be good to always use by default for all cores metrics. > > Thanks, > John
Thanks, Andrew
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