Round-robin scheduling

Updated: May 06, 2022

In round-robin scheduling, a thread selected to run continues executing until it:

As the following diagram shows, Thread A ran until it consumed its timeslice; the next READY thread (Thread B) now runs:

Figure 1. Round-robin scheduling.

A timeslice is the unit of time assigned to every process. Once it consumes its timeslice, a thread is preempted and the next READY thread at the same priority level is given control. A timeslice is 4 × the clock period. (For more information, see the entry for ClockPeriod() in the QNX Neutrino C Library Reference.)

Note: Apart from time slicing, round-robin scheduling is identical to FIFO scheduling.