Configuring Scheduling

Associated with both scheduling classes is a parameter table, rt_dptbl(4), and ts_dptbl(4). These tables are configurable by using a loadable module at boot time, or with dispadmin(1M) during runtime.

Dispatcher Parameter Table

The in-core table for real-time establishes the properties for RT scheduling. The rt_dptbl(4) structure consists of an array of parameters, struct rt_dpent_t. Each of the n priority levels has one parameter. The properties of a given priority level are specified by the ith parameter structure in the array, rt_dptbl[i].

A parameter structure consists of the following members, which are also described in the /usr/include/sys/rt.h header file.

rt_globpri

The global scheduling priority associated with this priority level. The rt_globpri values cannot be changed with dispadmin(1M).

rt_quantum

The length of the time quantum allocated to processes at this level in ticks. For more information, see Timestamp Interfaces. The time quantum value is only a default or starting value for processes at a particular level. The time quantum of a real-time process can be changed by using the priocntl(1) command or the priocntl(2) system call.

Reconfiguring config_rt_dptbl

A real-time administrator can change the behavior of the real-time portion of the scheduler by reconfiguring the config_rt_dptbl at any time. One method is described in the rt_dptbl(4) man page, in the section titled “Replacing the rt_dptbl Loadable Module.”

A second method for examining or modifying the real-time parameter table on a running system is through the dispadmin(1M) command. Invoking dispadmin(1M) for the real-time class enables retrieval of the current rt_quantum values in the current config_rt_dptbl configuration from the kernel's in-core table. When overwriting the current in-core table, the configuration file used for input to dispadmin(1M) must conform to the specific format described in the rt_dptbl(4) man page.

Following is an example of prioritized processes rtdpent_t with their associated time quantum config_rt_dptbl[] value as the processes might appear in config_rt_dptbl[].

Example 9–1 RT Class Dispatch Parameters

rtdpent_t  rt_dptbl[] = { 			129,    60,
	 /* prilevel Time quantum */							130,    40,
		100,    100,											131,    40,
		101,    100,											132,    40,
		102,    100,											133,    40,
		103,    100,											134,    40,
		104,    100,											135,    40,
		105,    100,											136,    40,
		106,    100,											137,    40,
		107,    100,											138,    40
		108,    100,											139,    40,
		109,    100,											140,    20,
		110,    80,											 141,    20,
		111,    80,											 142,    20,
		112,    80,											 143,    20,
		113,    80,											 144,    20,
		114,    80,											 145,    20,
		115,    80,											 146,    20,
		116,    80,											 147,    20,
		117,    80,											 148,    20,
		118,    80,											 149,    20,
		119,    80,											 150,    10,
		120,    60,											 151,    10,
		121,    60,											 152,    10,
		122,    60,											 153,    10,
		123,    60,											 154,    10,
		124,    60,											 155,    10,
		125,    60,											 156,    10,
		126,    60,											 157,    10,
		126,    60,											 158,    10,
		127,    60,											 159,    10,
		128,    60,										}