chrt

manipulate the real-time attributes of a process

SYNOPSIS

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

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, 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 Add SCHED_RESET_ON_FORK flag to the SCHED_FIFO or SCHED_RR scheduling policy (Linux-specific, supported since 2.6.31).

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

rml@tech9.net Robert Love
kzak@redhat.com Karel Zak

AVAILABILITY

The chrt command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.

DESCRIPTION

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

SEE ALSO

nice(1), renice(1), taskset(1), sched(7) See sched_setscheduler(2) for a description of the Linux scheduling scheme.

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