The current priorities came into FreeBSD with the original SMPng work ~20 years ago. Its not clear that there is a good reason to run network interrupts at a higher priority than anything else on the system. With the current priority scheme, network interrupt handlers on multi-queue NICs can consume all CPU in the system when under heavy receive load (such as during a denial of service attack), preventing things like callouts from running. One example of this behavior is the way lagg LACP links "flap" when a machine is under a DOS attack, due to the lacp_tick() callout not running.
Rather than playing whack-a-mole and reworking important callouts to use different mechanisms and priorities, I propose de-prioritizing network interrupt threads to be below SWIs. This has survived testing and production traffic at Netflix, and (with a second patch) allows LACP links to remain up for a DOS attack lasting over an hour, as it allows callouts to run.
I'm looking for comment and testing, and I'm particularly concerned for services like NFS and ISCSI where disks and network intersect, as this makes disks higher priority than network.