netmap overrun counters

[bazzoola]

Hi!

Two questions:

(1) Is there a way to know when netmap rx rings overrun? Most NIC
drivers provide MPC (missed packet count) and sysctl for rx_overrun.

I would like to know if my application is not reading as fast, i.e., no
frames are being dropped.

(2) What is the benefit of NETMAP_DO_RX_POLL? I do see the buffers being
updated when I set this flag but 'tail' is not advancing unless I read.

Bazz