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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.
POLICIES
       -o, --other
              Set scheduling policy to SCHED_OTHER.  This is the default Linux
              scheduling policy.
       -f, --fifo
              Set scheduling policy to SCHED_FIFO.
       -r, --rr
              Set  scheduling  policy to SCHED_RR.  When no policy is defined,
              the SCHED_RR is used as the default.
       -b, --batch
              Set scheduling policy to SCHED_BATCH (Linux-specific,  supported
              since 2.6.16).  The priority argument has to be set to zero.
       -i, --idle
              Set  scheduling  policy to SCHED_IDLE (Linux-specific, supported
              since 2.6.23).  The priority argument has to be set to zero.
       -d, --deadline
              Set scheduling policy to  SCHED_DEADLINE  (Linux-specific,  sup-
              ported  since  3.14).   The  priority  argument has to be set to
              zero.    See   also   --sched-runtime,   --sched-deadline    and
              --sched-period.   The  relation  between the options required by
              the kernel is runtime <= deadline <= period.  chrt copies period
              to deadline if --sched-deadline is not specified and deadline to
              runtime if --sched-runtime is not specified.  It means  that  at
              least --sched-period has to be specified.  See sched(7) for more
              details.
SCHEDULING OPTIONS
       -T, --sched-runtime nanoseconds
              Specifies runtime parameter for  SCHED_DEADLINE  policy  (Linux-
              specific).
       -P, --sched-period nanoseconds
              Specifies period parameter for SCHED_DEADLINE policy (Linux-spe-
              cific).
       -D, --sched-deadline nanoseconds
              Specifies deadline parameter for SCHED_DEADLINE  policy  (Linux-
              specific).
       -R, --reset-on-fork
              Use   SCHED_RESET_ON_FORK   or   SCHED_FLAG_RESET_ON_FORK  flag.
              Linux-specific, supported since 2.6.31.
              Each thread has a reset-on-fork scheduling flag.  When this flag
              is  set,  children  created by fork(2) do not inherit privileged
              scheduling policies.  After  the  reset-on-fork  flag  has  been
              enabled, it can be reset only if the thread has the CAP_SYS_NICE
              capability.  This flag is disabled in child processes created by
              fork(2).
              More  precisely, if the reset-on-fork flag is set, the following
              rules apply for subsequently created children:
              *  If the calling thread has a scheduling policy  of  SCHED_FIFO
                 or SCHED_RR, the policy is reset to SCHED_OTHER in child pro-
                 cesses.
              *  If the calling process has a negative nice  value,  the  nice
                 value is reset to zero in child processes.
OPTIONS
       -a, --all-tasks
              Set  or  retrieve  the  scheduling  attributes  of all the tasks
              (threads) for a given PID.
       -m, --max
              Show minimum and maximum valid priorities, then exit.
       -p, --pid
              Operate on an existing PID and do not launch a new task.
       -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
       nice(1), renice(1), taskset(1), sched(7)
       See  sched_setscheduler(2)  for  a  description of the Linux scheduling
       scheme.
AUTHORS
       Robert Love <rml AT tech9.net>
       Karel Zak <kzak AT redhat.com>
AVAILABILITY
       The chrt command is part of the util-linux  package  and  is  available
       from https://www.kernel.org/pub/linux/utils/util-linux/.
util-linux                       January 2016                          CHRT(1)