What is the goal of a round-robin CPU scheduling algorithm ?

Concept

CPU scheduling algorithms are each designed around a primary objective. Round-robin (RR) is a preemptive, time-sharing algorithm: every ready process is given a fixed time quantum in cyclic order, and a process that does not finish within its quantum is preempted and sent to the back of the ready queue. Its governing design goal is fair CPU sharing among all processes and good response time for interactive jobs.

Application

Because every process is served in turn for an equal slice, no process waits indefinitely and short interactive tasks get the CPU quickly, which keeps response time low. RR deliberately treats all processes uniformly rather than optimizing any single throughput or completion metric.

Contrast

• Minimizing the average waiting time is the defining strength of Shortest Job First (SJF/SRTF), which is provably optimal for that metric; round-robin generally produces a higher average waiting time than SJF because of frequent preemption and context switches.

• Prioritizing long-running processes or favouring I/O-bound versus CPU-bound jobs are properties of priority or specialized schedulers; round-robin gives every process the same quantum regardless of length or I/O behaviour.

• Maximizing CPU utilization and throughput is a general scheduling concern, but RR can lower throughput because each context switch adds overhead; raw utilization/throughput is not RR's distinguishing goal.

Note

None of the four options above states round-robin's actual objective — fair time-sharing with a good response time. The option that sounds closest, minimizing the average waiting time, is in fact Shortest Job First's defining goal, not round-robin's.