On Mon, 10 Feb 2025 15:28:19 +0000 Arinzon, David wrote:

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.