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
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
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.