Linux manual pages Section 1: General Commands  

Name

chrt — manipulate the real-time attributes of a process

Synopsis

chrt [options] prio command [arg...]

chrt [options] −p [prio] pid

DESCRIPTION

chrt sets or retrieves the real-time scheduling attributes of an existing pid, or runs command with the given attributes. Both policy (one of SCHED_OTHER, SCHED_FIFO, SCHED_RR, SCHED_BATCH, or SCHED_IDLE) and 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).

−f,−−fifo

Set scheduling policy to SCHED_FIFO.

−i,−−idle

Set scheduling policy to SCHED_IDLE (Linux specific).

−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,−−rr

Set scheduling policy to SCHED_RR. When policy is not defined the SCHED_RR is used as default.

−R,−−reset−on−fork

Add SCHED_RESET_ON_FORK flag to the SCHED_FIFO or SCHED_RR scheduling policy (Linux specific).

−v,−−verbose

Show status information.

−h,−−help

Display help text and exit.

−V,−−version

Display version information and exit.

USAGE

The default behavior is to run a new command:

chrt prio command[arguments]

You can also retrieve the real-time attributes of an existing task:

chrt −p pid

Or set them:

chrt −r −p prio 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.

AUTHOR

Written by Robert M. Love.

COPYRIGHT

Copyright © 2004 Robert M. Love

This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

taskset(1), nice(1), renice(1)

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

AVAILABILITY

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


  chrt(1) manpage

Copyright (C) 2004 Robert Love

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2002-05-11 Robert Love <rmltech9.net>
Initial version