I installed OS X Tiger in an emulator, to learn more about how OS X's UI has evolved over the years.

I noticed that Activity Monitor measures the percentage of CPU that is "Nice", in addition to the percentages which come from system processes, which come from user processes, and which are idle.

Tiger Activity Montior

What does "Nice" CPU usage represent? Are these system processes or user processes, and is there an equivalent in more modern OS X?

  • 1
    Did you see this question on serverfault? What does 'nice' mean on CPU utilization graphs?
    – lx07
    Jun 14, 2020 at 18:43
  • @lx07 No I had not! Thanks, that answers the question! So "Nice priority" processes can only run at the user level. Jun 14, 2020 at 23:35
  • It would appear so. Paraphrasing the serverfault answer it shows lowered priority (positive niceness) user processes. Perhaps this is of more interest on a server - idk. Looks like it was dropped by the time of 10.6 Snow Leopard - I couldn't find an Activity Monitor picture from 10.5 Leopard so perhaps it was still there at that time.
    – lx07
    Jun 15, 2020 at 7:40

1 Answer 1


Nice and renice are Unix commands where one can change the priority level of a process.

I used them on workstations many years ago to prioritize my job over other processes.

Will be found on man pages and most Unix books.

  • 1
    Thanks, but, what does that mean in the context of Activity Monitor? If they're merely lower-priority processes, shouldn't they still belong to either User or System? Jun 14, 2020 at 1:19

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