rtsched(1)

NAME

rtsched — execute process with real-time priority

SYNOPSIS

rtsched -s scheduler -p priority command [arguments]

rtsched [ -s scheduler ] -p priority -P pid

DESCRIPTION

Rtsched executes command with POSIX or HP-UX real-time priority, or changes the real-time priority of currently executing process pid.

All POSIX real-time priority processes are of greater scheduling importance than processes with HP-UX real-time or HP-UX timeshare priority. All HP-UX real-time priority processes are of greater scheduling importance than HP-UX timeshare priority processes, but are of lesser importance than POSIX real-time processes. Neither POSIX nor HP-UX real-time processes are subject to degradation. POSIX real-time processes may be scheduled with one of three different POSIX real-time schedulers: SCHED_FIFO, SCHED_RR, or SCHED_RR2. See rtsched(2) for details.

Rtsched is a superset of rtprio. See rtprio(1).

Options

-s scheduler

Specify the desired scheduler:

POSIX real-time schedulers:	SCHED_FIFO
	SCHED_RR
	SCHED_RR2
HP-UX real-time scheduler:	SCHED_RTPRIO
HP-UX timeshare scheduler:	SCHED_HPUX
	SCHED_NOAGE

-p priority

Specify priority range; any integer within the inclusive priority range of the corresponding scheduler. -p priority is required for all schedulers except SCHED_HPUX. If scheduler is SCHED_HPUX, the priority argument is ignored. The default priority range of each scheduler is as follows:

scheduler	highest priority	lowest priority
SCHED_FIFO	31	0
SCHED_RR	31	0
SCHED_RR2	31	0
SCHED_RTPRIO	0	127
SCHED_NOAGE	178	255
SCHED_HPUX	N/A	N/A

Note: Higher numerical values for the priority represent higher priorities under POSIX real-time schedulers, whereas lower numerical values for the priority represent higher priorities under HP-UX real-time and timeshare schedulers.

-P

Specify an already executing process ID (pid).

Command is not scheduled, or pid's real-time priority is not changed, if the user is not a member of a group having PRIV_RTSCHED access and is not the user with appropriate privileges. When changing the real-time priority of a currently executing process, the effective user ID of the calling process must be the user with appropriate privileges, or the real or effective user ID must match the real or saved user ID of the process to be modified.

In presence of processor sets (See pset_create(2) for details), the application execution is restricted to processors in the application's processor set. The threads in different processor sets do not compete with one another for processors based on their scheduling policy and priority values. The scheduler looks only at threads assigned to a processor's processor set to choose the next thread to run.

RETURN VALUE

rtsched returns exit status:

0: if command is successfully scheduled or if pid's real-time priority is successfully changed;
1: if command is not executable, pid does not exist, or priority is not within the priority range for the corresponding scheduler;
2: if command (pid) lacks real-time capability, or the invoker's effective user ID is not a user who has appropriate privileges, or the real or effective user or the real or effective user ID does not match the real or saved user ID of the process being changed; or
5: if rtsched encountered an internal error or if rtsched is not supported by this release.

EXAMPLES

Execute file a.out with SCHED_FIFO at a priority of 10:

rtsched -s SCHED_FIFO -p 10 a.out 

Execute file a.out with SCHED_RTPRIO at a priority of 127 (this is synonymous to rtprio 127 a.out):

rtsched -s SCHED_RTPRIO -p 127 a.out 

Execute file a.out with the SCHED_HPUX scheduler:

rtsched -s SCHED_HPUX a.out 

This is useful to spawn a timeshare priority command from a real-time priority shell.

Set the currently running process pid 24217 to execute with SCHED_RR2 at a priority of 20:

rtsched -s SCHED_RR2 -p 20 -P 24217 

Now change its priority to 10 using the same scheduler:

rtsched -p 10 -P 24217 

WARNINGS

Priority values used by rtsched may differ from those used by other commands. For example, ps(1) displays the internal representation of priority values.

AUTHOR

rtsched was developed by HP.

rtsched(1)

Technical documentation

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