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 exist-
       ing 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 (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 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/.



util-linux                         June 2010                           CHRT(1)
