mlx5: imissed versus prio0_buf_discards

[Tony Hart]

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?

many thanks,
tony

fyi: this is using DPKD 24.07 and the HWS RTE FLOW Api to setup the RSS
flow.  Firmware is 28.41
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