High CPU USAGE IN 2.7.0-RELEASE

[stephenw10]

em NICs are single queue. Only one CPU core can service the incoming and outgoing traffic queues. That means that on a 4 core CPU like you have it can never load all the cores.

igb NICs are multiqueue and here are attaching with 4 queues. Enough to load all the CPU cores sufficiently to prevent other services running.

You could override that by setting:

dev.igb.0.iflib.override_nrxqs=1
dev.igb.0.iflib.override_ntxqs=1

Or you could try to set a lower max interrupt rate like maybe:
hw.em.max_interrupt_rate=2000

But just swapping the WAN and LAN NIC assignments so LAN in em0 is probably easier. Unless you're not local to the box.