Usage:
 ionice [options] -p <pid>...
 ionice [options] -P <pgid>...
 ionice [options] -u <uid>...
 ionice [options] <command>

Show or change the I/O-scheduling class and priority of a process.

Options:
 -c, --class <class>    name or number of scheduling class,
                          0: none, 1: realtime, 2: best-effort, 3: idle
 -n, --classdata <num>  priority (0..7) in the specified scheduling class,
                          only for the realtime and best-effort classes
 -p, --pid <pid>...     act on these already running processes
 -P, --pgid <pgrp>...   act on already running processes in these groups
 -t, --ignore           ignore failures
 -u, --uid <uid>...     act on already running processes owned by these users

 -h, --help             display this help
 -V, --version          display version

For more details see ionice(1).