How to debug *BSD kernel (2)

remote debugger
need two (or more) machines, but very powerful.
you would be able to do almost everything you want:
set breakpoints, run-time variable examination, step-by-step execution...
procedure:
1. connect the target and working machines with a serial cable.
2. build kernel with KGDB support on the working machine.
3. boot the target machine with the KGDB-enabled kernel.
4. invoke gdb on the working machine and control the target machine by the gdb session.
for more details:
(FreeBSD) http://www.freebsd.org/handbook/x18366.html
(NetBSD) http://www.netbsd.org/Documentation/kernel/kgdb.html
(BSD/OS) http://www.v6.wide.ad.jp/Documents/debug.html

statistics
useful to find memory leakage or packet invalidity.
examples
"netstat -m": mbuf statistics
"netstat -s": general network statistics
"vmstat -m": kernel memory statistics