CHRT(1) 							   User Commands							   CHRT(1)

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 usage information 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 (C) 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 PARTICU-
       LAR 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/.

util-linux							     June 2010								   CHRT(1)