Process management

Scheduler commands and function calls

Below is a programmer's view of default LWP priorities. Fixed Class Priorities overlap the default Time-Sharing Priorities.

Process priorities (programmer view)

From a user or programmer's point of view, a process or LWP priority has meaning only in the context of a scheduler class. You specify an LWP priority by specifying a class and a class-specific priority value. The class and class-specific value are mapped by the system into a global priority that the system uses to schedule LWPs.

A system administrator's view of priorities is different from that of a user or programmer. When configuring scheduler classes, an administrator deals directly with global priorities. The system maps priorities supplied by users into these global priorities. See ``Process scheduling''.

The ps -cel command reports global priorities for all active processes and LWPs. The priocntl command reports the class-specific priorities that users and programmers use.

NOTE: Global priorities and user-supplied priorities are in ascending order: numerically higher priorities run first.

The priocntl(1) command and the priocntl(2), priocntllist(2), and priocntlset(2) system calls set or retrieve scheduler parameters for processes and LWPs. Setting priorities is similar for all these functions:

You specify the target processes and LWPs using an ID type and an ID. The ID type tells how to interpret the ID. (This concept of a set of processes and LWPs applies to signals as well as to the scheduler; see sigsend(2)). The following is a list of the valid priocntl ID types that you may specify.

process ID
parent process ID
process group ID
session ID
class ID
effective user ID
effective group ID
all processes

These IDs are basic properties of UNIX processes and LWPs. (See intro(2)). The class ID refers to the scheduler class of the process or LWP. priocntl works only for the time-sharing, fixed class, and the fixed priority classes, not for the system class. Processes in the system class have fixed priorities assigned when they are started by the kernel.

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UnixWare 7 Release 7.1.4 - 27 April 2004