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rtprio.2freebsd

BSD mandoc

NAME

rtprio - examine or modify a process realtime or idle priority

LIBRARY

Lb libc

SYNOPSIS

In sys/types.h In sys/rtprio.h Ft int Fn rtprio int function pid_t pid struct rtprio *rtp

DESCRIPTION

The Fn rtprio system call is used to lookup or change the realtime or idle priority of a process.

The Fa function argument specifies the operation to be performed. RTP_LOOKUP to lookup the current priority, and RTP_SET to set the priority. The Fa pid argument specifies the process to be used, 0 for the current process.

The Fa *rtp argument is a pointer to a struct rtprio which is used to specify the priority and priority type. This structure has the following form:

 struct rtprio {
         u_short type;
         u_short prio;
 };
 

The value of the type field may be RTP_PRIO_REALTIME for realtime priorities, RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities. The priority specified by the prio field ranges between 0 and RTP_PRIO_MAX (usually 31) 0 is the highest possible priority.

Realtime and idle priority is inherited through fork() and exec().

A realtime process can only be preempted by a process of equal or higher priority, or by an interrupt; idle priority processes will run only when no other real/normal priority process is runnable. Higher real/idle priority processes preempt lower real/idle priority processes. Processes of equal real/idle priority are run round-robin.

RETURN VALUES

Rv -std rtprio

ERRORS

The Fn rtprio system call will fail if

Bq Er EINVAL

The specified Fa prio was out of range.

Bq Er EPERM

The calling process is not allowed to set the realtime priority. Only root is allowed to change the realtime priority of any process, and non-root may only change the idle priority of the current process.

Bq Er ESRCH

The specified process was not found.

SEE ALSO

nice(1), ps(1), rtprio(1), setpriority(2), nice(3), renice(8)

AUTHORS

An -nosplit The original author was An Henrik Vestergaard Draboel Aq hvd@terry.ping.dk . This implementation in Fx was substantially rewritten by An David Greenman .