System Interface Guide

Utilities That Control Scheduling

The administrative utilities that control process scheduling are dispadmin(1M) and priocntl(1). Both 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 options shown in Table 8-2 are also available.

Table 8-2 Class Options for the dispadmin(1M) Utility




Lists scheduler classes currently configured 


Specifies the class whose parameters are to be displayed or 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 containing the dispatch parameters can also be loaded during runtime. Use this file to establish a new set of priorities replacing the default values 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 the example at the end of this section.

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

  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(1M) 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.