Sorry to barge in late, but IMO the timer should be on the host, which
is cheaper than on the guest (well, a 100ms timer is likely zero cost,
but I still don't like it).
the host should fire a tx completion interrupt whenever the completion
queue has "enough" entries, where we can define "enough" now as the
halfway mark or a timer expiry, whichever comes earlier.
We can later improve "enough" to be "just enough so the timer never
triggers" and adjust it dynamically. It probably doesn't matter for
Linux, but I don't want to punish guests that can do true async
networking and depend on timely completion notification.
This implies that we should not be supressing notifications in the guest at all (unless we're sure there are more packets to come, which currently we never are: that needs new net infrastructure).
But that means we'd get a notification on every xmit at the moment. Benchmarks anyone?