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/.