sorry for the delayed response.
Just wanted to check - your second and third test case was really on 80Mbps? That seems really low for drops to occur - especially with such settings (32 workers)… But you mention your CPU cores usage drops to 20 to 40%. That should never happen with DPDK - CPUs are supposed to keep polling on the NIC and have 100% CPU usage all the time (even with no packets coming in). That indicates something is really blocking the CPU cores. I did IPS tests for Suricon 2022 (talks available soon) and in there I had no problem with the performance). I had a full ET Open ruleset enabled with the performance of ~600 Mbps per worker (as usual for my CPU). It was running on 8 workers in total.
Just to be sure - can you try to increase the mempool size, cache size and rx/tx descriptors and see if it helps?
I would try something like this on both interfaces:
mempool-size: 262143
mempool-cache-size: 511
rx-descriptors: 8192
tx-descriptors: 8192
I would try running it on a lower number of cores - say 4 cores per interface.
Also, could you please attach perf top log?
Thanks.
Lukas