RE: [PATCH v6 net-next 3/4] net: ena: Add PHC documentation

["Arinzon, David" <darinzon@amazon.com>]

> > You are right in the regard that it is not a network specific functionality.
> > Having said that, PHC is a network card capability, making it a network-
> related component rather than purely a timekeeping feature.
> > Moreover we failed to find an existing tool which would allow users to get
> valuable feedback of the system's overall health.
> >
> > Researching its existing support in the kernel we noted that:
> > - PHC is embedded in network NIC and is supported by multiple NIC
> > vendors in the kernel
> > - PHC information is visible through ethtool -T
> > - The Linux networking stack uses PHC for timekeeping as well as for packet
> timestamping (via SO_TIMESTAMPING).
> >   Packet timestamping statistics are available through ethtool
> > get_ts_stats hook
> >
> > We have found `ethtool -S` as a suitable location for exposing these
> statistics, which are unique to the ENA NIC.
> >
> > We'd appreciate your thoughts on the matter, is there an alternative tool
> you can recommend?
> 
> We try to steer folks towards read-only debugfs files for stuff that's not
> strictly networking related. You also add a custom sysfs file in patch 4, I
> reckon adding stats there may also be a natural place for the user?
> 
> Patch 4 FWIW is lacking slightly in the justification, would be good to clarify
> why it's disabled by default. Single sentence of "why" would be great.

Hi Jakub,

Thank you for the feedback and the recommendations, we will incorporate them in v7.