util-linux
January 2016
util-linux
Miscellaneous system utilities for Linux
NAME
chrt - manipulate the real-time attributes of a process
SYNOPSIS
chrt [options] priority command [argument...]
chrt [options] -p [priority] pid
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 Love
Karel Zak
Karel 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/.
