chrt(1) - man - phpman

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 existing PID, or runs
       command with the given attributes.

POLICIES
       -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.

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-specific).

       -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 processes.

       •   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.

AUTHORS
       Robert Love <rml AT tech9.net>, Karel Zak <kzak AT redhat.com>

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

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

REPORTING BUGS
       For bug reports, use the issue tracker at https://github.com/karelzak/util-linux/issues.

AVAILABILITY
       The chrt command is part of the util-linux package which can be downloaded from Linux Kernel
       Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.



util-linux 2.37.2                            2021-06-02                                      CHRT(1)