Name
ionice — get/set program io scheduling class and
priority
Synopsis
ionice [−c] [−n] [−p] [ COMMAND [ ARG... ] ]
DESCRIPTION
This program sets the io scheduling class and priority for
a program. As of this writing, Linux supports 3 scheduling
classes:
Idle. A program
running with idle io priority will only get disk time when no
other program has asked for disk io for a defined grace
period. The impact of idle io processes on normal system
activity should be zero. This scheduling class does not take
a priority argument.
Best effort. This
is the default scheduling class for any process that hasn't
asked for a specific io priority. Programs inherit the CPU
nice setting for io priorities. This class takes a priority
argument from 0-7,
with lower number being higher priority. Programs running at
the same best effort priority are served in a round-robin
fashion.
Real time. The RT
scheduling class is given first access to the disk,
regardless of what else is going on in the system. Thus the
RT class needs to be used with some care, as it can starve
other processes. As with the best effort class, 8 priority
levels are defined denoting how big a time slice a given
process will receive on each scheduling window.
If no arguments or just −p is given,
ionice will
query the current io scheduling class and priority for that
process.
OPTIONS
−c-
The scheduling class. 1 for real time, 2 for
best-effort, 3 for idle.
−n-
The scheduling class data. This defines the class
data, if the class accepts an argument. For real time
and best-effort, 0-7 is valid data.
−p-
Pass in a process pid to change an already running
process. If this argument is not given,
ionice
will run the listed program with the given
parameters.
EXAMPLES
- # ionice -c3 -p89
- Sets process with PID 89 as an
idle io process.
- # ionice -c2 -n0 bash
- Runs 'bash' as a best-effort
program with highest priority.
- # ionice -p89
- Returns the class and priority of
the process with PID 89.
NOTES
Linux supports io scheduling priorities and classes since
2.6.13 with the CFQ io scheduler.
AUTHORS
Jens Axboe <axboe@suse.de>
