Empirical Evaluation of Modified Dynamic Time Quantum Round Robin Scheduling

Abstract

There are number of scheduling algorithms used in computer system today. They all have their own characteristics. Thus selection of the particular scheduling algorithm depends upon the need of the system. One of the most widely used scheduling algorithms in multiprogramming operating system is round robin. Round robin scheduling algorithm is most widely used scheduling algorithm in multitasking and real time environment. In RR scheduling the time quantum play a very important role, because if time quantum is very large then RR scheduling algorithm is same as the FCFS scheduling. If the time quantum is extremely too small then the number of context switches is very high. In recent days there is more research in dynamic quantum scheduling policies that can adopt automatically according to nature of incoming jobs. "Dynamic time quantum RR scheduling algorithm" is based on 'Q' which is the quantum for one complete round and 'n' number of jobs in ready queue. This research work modifies the quantum selection strategy in case of fraction (f) of jobs finished in previous round of round robin scheduling algorithm and the value of f is checked with 6.25%. If f is greater than or equal to 6.25% then the quantum value is decreased and if f is less than 6.25% then the quantum value is increased. And at last, experimentally verifies that modified algorithm policy gives better performance than dynamic time quantum RR scheduling policy by reducing number of context switches, average waiting time and average turnaround time. Keywords: RR scheduling, CPU scheduler, Dynamic quantum, Static quantum, context switches, AWT, ATT