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System Interface Guide

Function Calls That Control Scheduling

priocntl(2)

Control over scheduling of active classes is done with priocntl(2). Class attributes are inherited through fork(2) and exec(2), along with scheduling parameters and permissions required for priority control. This is true for both the RT and the TS classes.

The priocntl(2) function is the interface for specifying a real-time process, a set of processes, or a class to which the system call applies. priocntlset(2) also provides the more general interface for specifying an entire set of processes to which the system call applies.

The command arguments of priocntl(2) can be one of: PC_GETCID, PC_GETCLINFO, PC_GETPARMS, or PC_SETPARMS. The real or effective ID of the calling process must match that of the affected processes, or must have super-user privilege.

PC_GETCID

This command takes the name field of a structure that contains a recognizable class name (RT for real-time and TS for time-sharing). The class ID and an array of class attribute data are returned.  

PC_GETCLINFO

This command takes the ID field of a structure that contains a recognizable class identifier. The class name and an array of class attribute data are returned.  

PC_GETPARMS

This command returns the scheduling class identifier and/or the class specific scheduling parameters of one of the specified processes. Even though idtype & id might specify a big set, PC_GETPARMS returns the parameter of only one process. It is up to the class to select which one.

PC_SETPARMS

This command sets the scheduling class and/or the class specific scheduling parameters of the specified process or processes.  

sched_get_priority_max(3RT)

Returns the maximum values for the specified policy.

sched_get_priority_min(3RT)

Returns the minimum values for the specified policy (see sched_get_priority_max(3R)).

sched_rr_get_interval(3RT)

Updates the specified timespec structure to the current execution time limit (see sched_get_priority_max(3RT)).

sched_setparam(3RT), sched_getparam(3RT)

Sets or gets the scheduling parameters of the specified process.

sched_yield(3RT)

Blocks the calling process until it returns to the head of the process list.