Tunable Parameters

This section describes the tunable parameters that control scheduler configuration. To change any of these kernel parameters, enter a line in the /etc/system file with the format:

set parameter=value

See system(4) for more information.

The parameters described in this section control aspects of process scheduling, timesharing policy, and real-time policy.

The initial priority of a real-time process is determined when the process is put into the real-time scheduling class.

The priocntl -p command is used to specify the relative priority within the real-time class.

This is added to the base priority of the real-time class, which by default is 100. For example:

priocntl -e -c RT -p 20 command

This command would put the command into execution at a real-time priority of 120.

Process Scheduling Parameters

The following kernel parameters control aspects of process scheduling:

• maxclsyspri

  maxclsyspri is the maximum global priority of processes in the system class. When the kernel starts system processes, it assigns their priorities using the value of maxclsyspri as a reference point. maxclsyspri must have a value of 39 or greater, because the kernel assumes that the total range of system class priorities is at least 40.

  If you change this parameter, you must rebuild the scheduling class tables with values that correspond to the maximum priorities that you assign.

• sys_name

  sys_name is the character string name of the system scheduler class. The default value of sys_name is SYS.

Timesharing Policy

The following parameter is specified in the TS loadable module, which controls the timesharing policy:

• ts_maxupri

  ts_maxupri specifies the range within which users may adjust the priority of a timesharing process, using the priocntl(l) command or the priocntl(2) system call. The valid range for the user-supplied priority in the timesharing class is from +ts_maxupri to -ts_maxupri. The default value of ts_maxupri is 20 (which sets the range between +20 and -20, emulating the behavior of the older, less general scheduler interfaces, nice and setpriority.)

  The value of ts_maxupri is independent of the configured number of global timesharing priorities. In the default configuration, there are 0-59 timesharing priorities, but users may adjust their priorities only within a range of -20 to +20, relative to the system-calculated priority of the process. See "How to Designate a Process Priority" for more information.

  To change the value of this parameter, enter a line in /etc/system with the format:

  set TS:ts_maxupri=value
  

Real-Time Policy

The following parameter is specified in the RT loadable module, which controls the real-time policy:

• rt_maxpri

  rt_maxpri specifies the maximum priority to assign to real-time processes. The default value of rt_maxpri is 159.

  If you change this parameter, you must rebuild the scheduling class tables with values that correspond to the maximum priorities that you assign.

  To change the value of this parameter, enter a line in the /etc/system file with the format:

  set RT:rt_maxupri=value