chrt Man page

CHRT(1) User Commands CHRT(1)

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 exist‐
ing 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 supported 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.

OPTIONS

-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 pri‐
ority 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 prior‐
ity 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.

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

taskset, nice, renice

See sched_setscheduler(2) for a description of the Linux scheduling
scheme.

AUTHOR

Written by Robert M. Love.

COPRYRIGHT

Copyright © 2004 Robert M. Love. This is free software; see the source
for copying conditions. There is NO warranty; not even for MER‐
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

AVAILABILITY
The chrt command is part of the util-linux package and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux August 2014 CHRT(1)