Also, one other note: if we use sysfs, the directory structure will
be different depending on our chosen sysfs strategy. If we augment
netdev_rx_queue, the new attributes will be found in the standard
'rx-<N>' netdev subdirectory, e.g.,
/sys/class/net/eth0/queues/rx-0/mergeable_rx_buffer_size

Whereas if we use per-netdev attributes, our attributes would be in
/sys/class/net/eth0/<group name>/<attribute name>, which may be
less intuitive as AFAICT we'd have to indicate both the queue # and
type of value being reported using the attribute name. E.g.,
/sys/class/net/eth0/virtio-net/rx-0_mergeable_buffer_size.
That's somewhat less elegant.

I don't see an easy way to add new attributes to the 'rx-<N>'
subdirectories without directly modifying struct netdev_rx_queue,
so I think this is another tradeoff between the two sysfs approaches.

Best,

Mike