www.LinuxHowtos.org
CHRT
Section: User Commands (1)Updated: January 2016
Index Return to Main Contents
NAME
chrt - manipulate the real-time attributes of a processSYNOPSIS
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.SEE ALSO
nice(1), renice(1), taskset(1), sched(7)See sched_setscheduler(2) for a description of the Linux scheduling scheme.
AUTHORS
Robert LoveKarel Zak
AVAILABILITY
The chrt command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.