OPTIONS
-c, --class class
Specify the name or number of the scheduling class to use;
0 for none, 1 for realtime, 2 for best-effort, 3 for idle.
-n, --classdata level
Specify the scheduling class data. This only has an effect if the class accepts an argument.
For real-time and best-effort, 0-7 are valid data (priority levels).
# nice -n 19 ionice -c 2 -n 7 COMMAND
# ionice -p 27367
unknown: prio 4
# ionice -c 3 -p 27367
# ionice -p 27367
idle
#
# ionice -c 2 -p 27367
# ionice -p 27367
best-effort: prio 4
#