CHRT(1) - man page online | user commands

Manipulate the real-time attributes of a process.

August 2014
CHRT(1)                                   User Commands                                   CHRT(1)


chrt - manipulate the real-time attributes of a process


chrt [options] priority command [argument...] chrt [options] -p [priority] pid


chrt sets or retrieves the real-time scheduling attributes of an existing pid, or runs command with the given attributes. Both the policy (one of SCHED_OTHER, SCHED_FIFO, SCHED_RR, SCHED_BATCH, or SCHED_IDLE) and the priority can be set and retrieved. The SCHED_BATCH policy is supported since Linux 2.6.16. The SCHED_IDLE policy is sup‐ ported since Linux 2.6.23. The SCHED_RESET_ON_FORK flag for policies SCHED_RR and SCHED_FIFO is supported since Linux 2.6.31.


-a, --all-tasks Set or retrieve the scheduling attributes of all the tasks (threads) for a given PID. -b, --batch Set scheduling policy to SCHED_BATCH (Linux-specific). The priority argument has to be set to zero. -f, --fifo Set scheduling policy to SCHED_FIFO. -i, --idle Set scheduling policy to SCHED_IDLE (Linux-specific). The priority argument has to be set to zero. -m, --max Show minimum and maximum valid priorities, then exit. -o, --other Set policy scheduling policy to SCHED_OTHER. -p, --pid Operate on an existing PID and do not launch a new task. -R, --reset-on-fork Add SCHED_RESET_ON_FORK flag to the SCHED_FIFO or SCHED_RR scheduling policy (Linux-specific). -r, --rr Set scheduling policy to SCHED_RR. When policy is not defined the SCHED_RR is used as default. -v, --verbose Show status information. -V, --version Display version information and exit. -h, --help Display help text and exit.


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


A user must possess CAP_SYS_NICE to change the scheduling attributes of a process. Any user can retrieve the scheduling information.


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.


taskset(1), nice(1), renice(1) See sched_setscheduler(2) for a description of the Linux scheduling scheme.


Written by Robert M. Love.
Copyright © 2004 Robert M. Love. This is free software; see the source for copying condi‐ tions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


The chrt command is part of the util-linux package and is available from ftp://ftp.ker‐
util-linux August 2014 CHRT(1)
This manual Reference Other manuals
chrt(1) referred by cset(1) | cset-proc(1) | cset-set(1) | cset-shield(1) | sched(7) | sched_setattr(2) | sched_setscheduler(2) | taskset(1) | xboxdrv(1)
refer to nice(1) | renice(1) | sched_setscheduler(2) | taskset(1)