Programming Interfaces Guide

Utilities That Control Scheduling

The administrative utilities that control process scheduling are dispadmin(1M) and priocntl(1). Both of these utilities support the priocntl(2) system call with compatible options and loadable modules. These utilities provide system administration functions that control real-time process scheduling during runtime.


The priocntl(1) command sets and retrieves scheduler parameters for processes.


The dispadmin(1M) utility displays all current process scheduling classes by including the -l command line option during runtime. Process scheduling can also be changed for the class specified after the -c option, using RT as the argument for the real-time class.

The class options for dispadmin(1M) are in the following list:


Lists scheduler classes currently configured


Specifies the class with parameters to be displayed or to be changed


Gets the dispatch parameters for the specified class


Used with -g, specifies time quantum resolution


Specifies a file where values can be located

A class-specific file that contains the dispatch parameters can also be loaded during runtime. Use this file to establish a new set of priorities that replace the default values that were established during boot time. This class-specific file must assert the arguments in the format used by the -g option. Parameters for the RT class are found in the rt_dptbl(4), and are listed in Example 12–1.

To add an RT class file to the system, the following modules must be present:

The following steps install a RT class dispatch table:

  1. Load the class-specific module with the following command, where module_name is the class-specific module.

    # modload /kernel/sched/module_name
  2. Invoke the dispadmin command.

    # dispadmin -c RT -s file_name

    The file must describe a table with the same number of entries as the table that is being overwritten.