CONTAP-777838: ONTAP cluster node reboots unexpectedly

An ONTAP cluster node reboots unexpectedly:
PANIC: Process <process_name> unresponsive for <seconds> seconds ... in process nodewatchdog

The process name can be mgwd, secd, or bcomd, the process can be unresponsive for varying durations (in seconds) and it does not recover.
A generic node watchdog signature is not sufficient to match this issue. The disruption event must also have the FreeBSD memory-exhaustion signature:

• FreeBSD wired memory consumes nearly all of the BSD memory partition.
  All known incidents show approximately 94% or more of wired memory.
• Available BSD memory is reduced to a few hundred MB or less.
• Systemshell top -bS output shows high Wired and low free memory usage.

Use the systemshell command with NetApp Support guidance to determine the current mhost memory usage by running the top command. For example:
cluster::> set -privilege diagnostic
cluster::*> systemshell -node <node_name> -command "top -bS | head -n 5"
last pid: 78952; load averages: 29.70, 28.44, 26.02 up 138+18:44:26
3339 processes:72 running, 282 sleeping, 2 zombie, 2983 waiting
CPU: 2.3% user, 0.0% nice, 36.9% system, 0.1% interrupt, 60.7% idle
Mem: 62M Active, 1132K Inact, 3532K Laundry, 15G Wired, 905M Buf, 253M Free
Swap: 8192M Total, 1400M Used, 6792M Free, 17% Inuse