chrt(1) — Linux manual page


CHRT(1)                       User Commands                      CHRT(1)

NAME         top

       chrt - manipulate the real-time attributes of a process

SYNOPSIS         top

       chrt [options] priority command [argument...]
       chrt [options] -p [priority] pid

DESCRIPTION         top

       chrt sets or retrieves the real-time scheduling attributes of an
       existing pid, or runs command with the given attributes.

POLICIES         top

       -o, --other
              Set scheduling policy to SCHED_OTHER (time-sharing
              scheduling).  This is the default Linux scheduling policy.

       -f, --fifo
              Set scheduling policy to SCHED_FIFO (first in-first out).

       -r, --rr
              Set scheduling policy to SCHED_RR (round-robin
              scheduling).  When no policy is defined, the SCHED_RR is
              used as the default.

       -b, --batch
              Set scheduling policy to SCHED_BATCH (scheduling batch
              processes).  Linux-specific, supported since 2.6.16.  The
              priority argument has to be set to zero.

       -i, --idle
              Set scheduling policy to SCHED_IDLE (scheduling very low
              priority jobs).  Linux-specific, supported since 2.6.23.
              The priority argument has to be set to zero.

       -d, --deadline
              Set scheduling policy to SCHED_DEADLINE (sporadic task
              model deadline scheduling).  Linux-specific, supported
              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.


       -T, --sched-runtime nanoseconds
              Specifies runtime parameter for SCHED_DEADLINE policy

       -P, --sched-period nanoseconds
              Specifies period parameter for SCHED_DEADLINE policy

       -D, --sched-deadline nanoseconds
              Specifies deadline parameter for SCHED_DEADLINE policy

       -R, --reset-on-fork
              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 processes.

              *  If the calling process has a negative nice value, the
                 nice value is reset to zero in child processes.

OPTIONS         top

       -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         top

       The default behavior is to run a new command:
              chrt priority command [arguments]

       You can also retrieve the real-time attributes of an existing
              chrt -p pid

       Or set them:
              chrt -r -p priority pid

PERMISSIONS         top

       A user must possess CAP_SYS_NICE to change the scheduling
       attributes of a process.  Any user can retrieve the scheduling

NOTES         top

       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.

AUTHORS         top

       Robert Love ⟨⟩
       Karel Zak ⟨⟩

SEE ALSO         top

       nice(1), renice(1), taskset(1), sched(7)

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

AVAILABILITY         top

       The chrt command is part of the util-linux package and is
       available from

COLOPHON         top

       This page is part of the util-linux (a random collection of Linux
       utilities) project.  Information about the project can be found
       at ⟨⟩.  If you
       have a bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

util-linux                    January 2016                       CHRT(1)

Pages that refer to this page: renice(1)taskset(1)sched_setattr(2)sched_setscheduler(2)sched(7)