You can change the default priority that an application runs with by starting it with the nice command, but if you want to change the priority of a process that is already running, the command to use is renice.
Renice can be used to change the priority of a single process, or of all the processes owned by a specified user. As with the nice command, the priority values range from -20 to +19 and negative numbers raise the priority of a task while positive numbers lower it. Yes, that seems a little backwards, but the higher the priority the less resources are devoted to it. Only the superuser can specify negative numbers (thus raising the priority of a process).
renice 5 some_process
This command will change the priority of some_process to 5.
renice -5 -u erik
will change the priority of all processes owned by user erik to -5.
renice -5 -u erik -p 699
will chance the priority of all processes owned by erik and process with PID 699 to -5.Tweet