"From the command line (Terminal.app or whatever) use nice and renice, just like on other unixes.
Use nice when launching a process:
nice -n <priority> <command> <arguments to command>
The default priority is zero, positive values are ""nicer"" (that is lower priority) and negative values are ""less nice"" (higher priority). Looks like Mac OS runs from +10 to -10.
Use renice to change the priority of a process already running (from the renice man page on 10.5):
renice priority [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]
renice -n increment [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]
The part you're interested in here is the pid bit. That is the process id for the job and you can find it using ps -u <your username> and looking for the process name, but I prefer top -o in this case, because the process you're interested in will be near the top.
Note: Without superuser privileges you can never increase a process's priority. For normal users, nice and renice are one way streets. And small changes in priority can have large effects on running time. So go easy on this until you understand it."
