Re: Feedback requested: Exposing NVDIMM performance statistics in a generic way

["Michal Suchánek" <msuchanek@suse.de>]

Hello,

On Thu, May 28, 2020 at 11:59 AM Vaibhav Jain <vaibhav@linux.ibm.com> wrote:
>
> Thanks for this taking time to look into this Dan,
>
> Agree with the points you have made earlier that I am summarizing below:
>
> * This is better done in ndctl rather than ipmctl.
> * Should only expose general performance metrics and not performance
>   counters. Performance counter should be exposed via perf
> * Vendor specific metrics to be separated from generic performance
>   metrics.
>
> One way to split generic and vendor specific metrics might be to report
> generic performance metrics together with dimm health metrics such as
> "temprature_celsius" or "spares_percentage" that are already reported in
> by dimm health output.
>
> Vendor specific performance metrics can be reported as a seperate object
> in the json output. Something similar to output below:
>
> # ndctl list -DH --stats --vendor-stats
> [
>   {
>     "dev":"nmem0",
>     "health":{
>       "health_state":"ok",
>       "shutdown_state":"clean",
>       "temperature_celsius":48.00,
>       "spares_percentage":10,
>
>       /* Generic performance metrics/stats */
>       "TotalMediaReads": 18929,
>       "TotalMediaWrites": 0,
>       ....
>     }
>
>     /* Vendor specific stats for the dimm */
>     "vendor-stats": {
>     "Controller Reset Count":10
>     "Controller Reset Elapsed Time": 3600
>     "Power-on Seconds": 3600

How do you tell generic from vendor-specific stats, though?

Controller reset count and power-on time may not be reported by some
controllers but sound pretty generic.

Even if you declare that the stats reported by all controllers
available at this moment are generic a later one may not report some of
these 'generic' statistics, or report them in different way/units, or
may simply not report anything at all for some technical reason.

Kernels that do not have this feature will not report anything at all
either.

Thanks

Michal
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