Round robin (RR) is one of the simplest, oldest, fairest and most extensively used algorithms.
• In the round robin scheduling, processes are posted in a FIFO manner but are given a limited amount of CPU time known as a time-slice or a quantum.
• If a process does not complete previous to its CPU-time expires, the CPU is preempted and given to the next process waiting in a queue. The preempted process is then positioned at the back of the ready list.
• Round Robin Scheduling is preemptive (at the end of time-slice) consequently it is effective in time-sharing environments in which the system needs to assurance reasonable response times for interactive users.
• The only interesting matter with round robin scheme is the length of the quantum. Putting the quantum too short causes too many context switches and lower the CPU competence. Conversely, setting the quantum too long may cause poor response time and approximates FCFS.
• In any occurrence, the average waiting time under round robin scheduling is often fairly long.