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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | EXAMPLES | AUTHORS | SEE ALSO | AVAILABILITY | COLOPHON |
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IONICE(1) User Commands IONICE(1)
ionice - set or get process I/O scheduling class and priority
ionice [-c class] [-n level] [-t] -p PID...
ionice [-c class] [-n level] [-t] -P PGID...
ionice [-c class] [-n level] [-t] -u UID...
ionice [-c class] [-n level] [-t] command [argument...]
This program sets or gets the I/O scheduling class and priority
for a program. If no arguments or just -p is given, ionice will
query the current I/O scheduling class and priority for that
process.
When command is given, ionice will run this command with the
given arguments. If no class is specified, then command will be
executed with the "best-effort" scheduling class. The default
priority level is 4.
As of this writing, a process can be in one of three scheduling
classes:
Idle A program running with idle I/O priority will only get
disk time when no other program has asked for disk I/O for
a defined grace period. The impact of an idle I/O process
on normal system activity should be zero. This scheduling
class does not take a priority argument. Presently, this
scheduling class is permitted for an ordinary user (since
kernel 2.6.25).
Best-effort
This is the effective scheduling class for any process
that has not asked for a specific I/O priority. This
class takes a priority argument from 0-7, with a lower
number being higher priority. Programs running at the
same best-effort priority are served in a round-robin
fashion.
Note that before kernel 2.6.26 a process that has not
asked for an I/O priority formally uses "none" as
scheduling class, but the I/O scheduler will treat such
processes as if it were in the best-effort class. The
priority within the best-effort class will be dynamically
derived from the CPU nice level of the process:
io_priority = (cpu_nice + 20) / 5.
For kernels after 2.6.26 with the CFQ I/O scheduler, a
process that has not asked for an I/O priority inherits
its CPU scheduling class. The I/O priority is derived
from the CPU nice level of the process (same as before
kernel 2.6.26).
Realtime
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.
This scheduling class is not permitted for an ordinary
(i.e., non-root) user.
-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 realtime and
best-effort, 0-7 are valid data (priority levels), and 0
represents the highest priority level.
-p, --pid PID...
Specify the process IDs of running processes for which to
get or set the scheduling parameters.
-P, --pgid PGID...
Specify the process group IDs of running processes for
which to get or set the scheduling parameters.
-t, --ignore
Ignore failure to set the requested priority. If command
was specified, run it even in case it was not possible to
set the desired scheduling priority, which can happen due
to insufficient privileges or an old kernel version.
-h, --help
Display help text and exit.
-u, --uid UID...
Specify the user IDs of running processes for which to get
or set the scheduling parameters.
-V, --version
Display version information and exit.
Linux supports I/O scheduling priorities and classes since 2.6.13
with the CFQ I/O scheduler.
# ionice -c 3 -p 89
Sets process with PID 89 as an idle I/O process.
# ionice -c 2 -n 0 bash
Runs 'bash' as a best-effort program with highest priority.
# ionice -p 89 91
Prints the class and priority of the processes with PID 89 and
91.
Jens Axboe <jens@axboe.dk>
Karel Zak <kzak@redhat.com>
ioprio_set(2)
The ionice command is part of the util-linux package and is
available from
https://www.kernel.org/pub/linux/utils/util-linux/.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found
at ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you
have a bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-12-17.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
util-linux July 2011 IONICE(1)
Pages that refer to this page: ioprio_set(2), btrfs-scrub(8), iotop(8)
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