NAME
rtprio, idprio
— execute, examine or modify a
utility's or process's realtime or idletime scheduling priority
SYNOPSIS
[id|rt]prio |
[id|rt]prio |
[-]pid |
[id|rt]prio |
priority command [args] |
[id|rt]prio |
priority
-pid |
[id|rt]prio |
-t command [args] |
[id|rt]prio |
-t
-pid |
DESCRIPTION
Thertprio utility is used for controlling realtime
process scheduling.
The idprio utility is used for controlling
idletime process scheduling, and can be called with the same options as
rtprio.
A process with a realtime priority is not subject to priority degradation, and will only be preempted by another process of equal or higher realtime priority.
A process with an idle priority will run only when no other process is runnable and then only if its idle priority is equal or greater than all other runnable idle priority processes.
Both rtprio or
idprio when called without arguments will return the
realtime priority of the current process.
If rtprio is called with 1 argument, it
will return the realtime priority of the process with the specified
pid.
If priority is specified, the process or
program is run at that realtime priority. If -t is
specified, the process or program is run as a normal (non-realtime)
process.
If -pid is specified, the process with the process identifier pid will be modified, else if command is specified, that program is run with its arguments.
Priority is an integer between 0 and RTP_PRIO_MAX (usually 31). 0 is the highest priority
Pid of 0 means "the current process".
Only root is allowed to set realtime or idle priority for a process.
EXIT STATUS
If rtprio execute a command, the exit
value is that of the command executed. In all other cases,
rtprio exits 0 on success, and 1 for all other
errors.
EXAMPLES
To see which realtime priority the current process is at:
rtprio
To see which realtime priority of process 1423:
rtprio 1423
To run cron(8) at the lowest realtime priority:
rtprio 31 cron
To change the realtime priority of process 1423 to 16:
rtprio 16 -1423
To run tcpdump(1) without realtime priority:
rtprio -t tcpdump
To change the realtime priority of process 1423
to RTP_PRIO_NORMAL (non-realtime/normal
priority):
rtprio -t -1423
To make depend while not disturbing other machine usage:
SEE ALSO
nice(1), ps(1), rtprio(2), setpriority(2), nice(3), renice(8)
HISTORY
The rtprio utility appeared in
FreeBSD 2.0, but is similar to the HP-UX
version.
AUTHORS
Henrik Vestergaard Draboel <hvd@terry.ping.dk> is the original author. This implementation was substantially rewritten by David Greenman.
CAVEATS
You can lock yourself out of the system by placing a cpu-heavy process in a realtime priority.
BUGS
There is no way to set/view the realtime priority of process 0 (swapper) (see ps(1)).
There is in DragonFly no way to ensure that a process page is present in memory therefore the process may be stopped for pagein (see mprotect(2), madvise(2)).
Under DragonFly system calls are currently never preempted, therefore non-realtime processes can starve realtime processes, or idletime processes can starve normal priority processes.