CHRT
Section: User Commands (1)
Updated: January 2016
Page Index
NAME
chrt - manipulate the real-time attributes of a process
SYNOPSIS
chrt
[options]
priority command [
argument...]
chrt
[options]
-p
[
priority]
pid
DESCRIPTION
chrt
sets or retrieves the real-time scheduling attributes of an existing
pid,
or runs
command with the given attributes.
POLICIES
- -o, --other
-
Set scheduling policy to
SCHED_OTHER.
This is the default Linux scheduling policy.
- -f, --fifo
-
Set scheduling policy to SCHED_FIFO.
- -r, --rr
-
Set scheduling policy to
SCHED_RR.
When no policy is defined, the
SCHED_RR
is used as the default.
- -b, --batch
-
Set scheduling policy to
SCHED_BATCH
(Linux-specific, supported since 2.6.16). The priority argument has to be set to zero.
- -i, --idle
-
Set scheduling policy to
SCHED_IDLE
(Linux-specific, supported since 2.6.23). The priority argument has to be set to zero.
- -d, --deadline
-
Set scheduling policy to
SCHED_DEADLINE
(Linux-specific, supported since 3.14). The priority argument has to be set to zero.
See also --sched-runtime, --sched-deadline and
--sched-period. The relation between the options required by the kernel is
runtime <= deadline <= period.
chrt
copies period to deadline if --sched-deadline is not specified and
deadline to runtime if --sched-runtime is not specified.
It means that at least --sched-period has to be specified. See
sched(7)
for more details.
SCHEDULING OPTIONS
- -T, --sched-runtime nanoseconds
-
Specifies runtime parameter for SCHED_DEADLINE policy (Linux-specific).
- -P, --sched-period nanoseconds
-
Specifies period parameter for SCHED_DEADLINE policy (Linux-specific).
- -D, --sched-deadline nanoseconds
-
Specifies deadline parameter for SCHED_DEADLINE policy (Linux-specific).
- -R, --reset-on-fork
-
Add
SCHED_RESET_ON_FORK
flag to the
SCHED_FIFO
or
SCHED_RR
scheduling policy (Linux-specific, supported since 2.6.31).
OPTIONS
- -a, --all-tasks
-
Set or retrieve the scheduling attributes of all the tasks (threads) for a
given PID.
- -m, --max
-
Show minimum and maximum valid priorities, then exit.
- -p, --pid
-
Operate on an existing PID and do not launch a new task.
- -v, --verbose
-
Show status information.
- -V, --version
-
Display version information and exit.
- -h, --help
-
Display help text and exit.
USAGE
- The default behavior is to run a new command:
-
chrt
priority
command [arguments]
- You can also retrieve the real-time attributes of an existing task:
-
chrt -p
pid
- Or set them:
-
chrt -r -p
priority pid
PERMISSIONS
A user must possess
CAP_SYS_NICE
to change the scheduling attributes of a process. Any user can retrieve the
scheduling information.
NOTES
Only
SCHED_FIFO,
SCHED_OTHER
and
SCHED_RR
are part of POSIX 1003.1b Process Scheduling. The other scheduling attributes
may be ignored on some systems.
Linux' default scheduling policy is
SCHED_OTHER.
AUTHORS
Robert Love
Karel Zak
SEE ALSO
nice(1),
renice(1),
taskset(1),
sched(7)
See
sched_setscheduler(2)
for a description of the Linux scheduling scheme.
AVAILABILITY
The chrt command is part of the util-linux package and is available from
https://www.kernel.org/pub/linux/utils/util-linux/.