mbq_len
nm_prdis("have %d pkts in queue", mbq_len(&q));
n = mbq_len(q);
if (busy + mbq_len(q) >= kring->nkr_num_slots - 1) {
kring->nr_hwcur, kring->nr_hwtail, mbq_len(q));
nm_prdis(2, "%s %d bufs in queue", na->name, mbq_len(q));
nm_prdis("destroy sw mbq with len %d", mbq_len(q));
} else if (unlikely(mbq_len(&kring->rx_queue) > na->num_rx_desc)) {