renice - alter priority of running processes
renice -n priority [options] <pid> [...]
Renice alters the scheduling priority of one or more running processes. The following who parameters are inter-preted as process ID's, process group ID's, or user names. Renice'ing a process group causes all processes in the process group to have their scheduling priority altered.
Renice'ing a user causes all processes owned by the user to have their scheduling priority altered.
By default, the processes to be affected are specified by their process ID's.
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'' (for security reasons) within the range 0 to PRIO_MAX (20), unless a nice resource limit is set (Linux 2.6.12 and higher).
The super-user may alter the priority of any process and set the prior‐ity 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), anything negative (to make things go very fast)