Multithreaded Programming Guide

Timeshare Scheduling

Timeshare scheduling distributes the processing resource fairly among the LWPs in this scheduling class. Other parts of the kernel can monopolize the processor for short intervals without degrading response time as seen by the user.

The priocntl(2) call sets the nice(2) level of one or more processes. The priocntl() call also affects the nice() level of all the timesharing class LWPs in the process. The nice() level ranges from 0 to +20 normally and from -20 to +20 for processes with superuser privilege. The lower the value, the higher the priority.

The dispatch priority of time shared LWPs is calculated from the instantaneous CPU use rate of the LWP and from its nice() level. The nice() level indicates the relative priority of the LWPs to the timeshare scheduler.

LWPs with a greater nice() value get a smaller, but nonzero, share of the total processing. An LWP that has received a larger amount of processing is given lower priority than one that has received little or no processing.