sysctl kern.ipc.shm* description ?

[bruno schwander]

Is there a good explanation of what those variables are and the
dangers/advantages of changing them ?

I ask because I determined one port (multimedia/nuppelvideo) needs more
shared memory to run (on my system). But when I changed some of the
kern.ipc.shm* sysctl, the program ran for 15 sec and then the system froze
and rebooted after a couple seconds.

bruno