Man Pages

CHRT


NAME
SYNOPSIS
DESCRIPTION
OPTIONS
USAGE
PERMISSIONS
NOTES
SEE ALSO
AUTHOR
COPYRIGHT
AVAILABILITY

NAME

chrt − manipulate the real-time attributes of a process

SYNOPSIS

chrt [options] priority command [argument...]
chrt
[options] −p [prioritypid

DESCRIPTION

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 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 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.

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

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

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.

AVAILABILITY

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

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