macrumors 65816
Original poster
May 6, 2005
Bay Area
Question! Is there a way to set the priority of a certain process in OSX? Whenever i'm rendering something in Final Cut Pro or any other program, it slows down the whole system (duh), but whenever i'm doing something under windows (rendering 3D or whatever) I can turn down the the priority in the task manager (where would windows be without CTRL+ALT+DELETE) so the whole system doesent slow down to a crawl and I can contunue to do other things while the system is busy rendering. I know it will take a little longer to render depending on whatever else im doing, but i hate slowdowns so much (especially a slow dock).

Sometimes render times go on for hours and it wouldn't seem as painful if I was able to do other things without the WHOLE system being so slow.


macrumors 68020
Jun 18, 2003
Use activity monitor to find the ProcessID of the process of interest, then use the 'renice' command in Terminal.

"man renice":

RENICE(8) BSD System Manager's Manual RENICE(8)

renice -- alter priority of running processes

renice priority [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]
renice -n increment [[-p] pid ...] [[-g] pgrp ...] [[-u] user ...]

The renice utility alters the scheduling priority of one or more running
processes. The following who parameters are interpreted as process ID's,
process group ID's, user ID's or user names. The renice'ing of a process
group causes all processes in the process group to have their scheduling
priority altered. The renice'ing of a user causes all processes owned by
the user to have their scheduling priority altered. By default, the pro-
cesses to be affected are specified by their process ID's.

The following options are available:

-g Force who parameters to be interpreted as process group ID's.

-n Instead of changing the specified processes to the given prior-
ity, interpret the following argument as an increment to be
applied to the current priority of each process.

-u Force the who parameters to be interpreted as user names or user

-p Reset the who interpretation to be (the default) process ID's.

For example,

renice +1 987 -u daemon root -p 32

would change the priority of process ID's 987 and 32, and all processes
owned by users daemon and root.

Users other than the super-user may only alter the priority of processes
they own, and can only monotonically increase their ``nice value'' within
the range 0 to PRIO_MAX (20). (This prevents overriding administrative
fiats.) The super-user may alter the priority of any process and set the
priority to any value in the range PRIO_MIN (-20) to PRIO_MAX. Useful
priorities are: 20 (the affected processes will run only when nothing
else in the system wants to), 0 (the ``base'' scheduling priority), any-
thing negative (to make things go very fast).


macrumors 65816
Apr 15, 2004
So pretty much from the description above, their is no easy way like bringing up the task manager, right clicking and setting the priority.

I read that ^ up their and am 100x more confused than I was before I read it.

So I dont know what to do either.


macrumors 68020
Jun 18, 2003
Basically, you find the process ID you're interested in via Activity Monitor or by running "ps Ac" in Terminal. I'm assuming that you want to change the priority of a process that's already running. Once you have the PID, then run "sudo renice -20 PID" from the Terminal. You have to have admin privileges to run this command, and you will have to enter your password. The "-20" sets the process priority to its highest value; you would use a priority of "20" to set it to its lowest value. I know this sounds backwards, but it's not.

If you are starting a process from Terminal, use the "nice" command.

You might want to look at "man setpriority" for additional information, although this is *not* a command, it's a system call, i.e. you would use it from within a program you are coding.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.