I have a simple DPDK app that receives packets via RSS from a CX7 (400G).  The app uses 16 queues across 16 cores.  What I see is dropped packets even at only 50Mpps.

Looking at rte_eth_port_xstats() I see  rx_prio0_buf_discard_packets matches the number of packets dropped however the imissed counter (from rte_eth_port_stats) is 0.  Indeed when I look at the rx_queue depths from each thread in the app they barely reach 30 entries (I'm using the default number of queue descs).

What is the difference between rx_prio0_buf_discards and imissed counters, why would rx_prio0_buf_discards increase but not imissed?