chrt - manipulate the real-time attributes of a process
priority command argument ...
chrt [options] -p [
chrt sets or retrieves the real-time scheduling attributes of an existing
PID, or runs
command with the given attributes.
Set scheduling policy to SCHED_OTHER (time-sharing scheduling). This is the default Linux scheduling policy.
Set scheduling policy to SCHED_FIFO (first in-first out).
Set scheduling policy to SCHED_RR (round-robin scheduling). When no policy is defined, the SCHED_RR is used as the default.
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.
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.
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
deadlineif --sched-deadline is not specified and
runtimeif --sched-runtime is not specified. It means that at least --sched-period has to be specified. See sched(7) for more details.
Specifies runtime parameter for SCHED_DEADLINE policy (Linux-specific).
Specifies period parameter for SCHED_DEADLINE policy (Linux-specific).
Specifies deadline parameter for SCHED_DEADLINE policy (Linux-specific).
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.
Set or retrieve the scheduling attributes of all the tasks (threads) for a given PID.
Show minimum and maximum valid priorities, then exit.
Operate on an existing PID and do not launch a new task.
Show status information.
Display version information and exit.
Display help text and exit.
The default behavior is to run a new command:
You can also retrieve the real-time attributes of an existing task:
Or set them:
chrt -r -p
A user must possess CAP_SYS_NICE to change the scheduling attributes of a process. Any user can retrieve the scheduling information.
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.