Enhanced Process Scheduling In Longest Job First Algorithm With Combinational Burst Time

Longest Job First (LJF), the opposite of Shortest Job First, has been an unpopular processscheduling algorithm. The idea of combinational burst time was used to avoid the starvationproblem associated with the LJF algorithm and to make it compete with other schedulingalgorithms with respect to some performance metrics. Although the combinational burst timeproposal led to improved performance, the work suffers from the limitations that the averagewaiting time and the average turnaround time were slightly higher, and the number of contextswitches was a little higher also. The research reported in this dissertation addressed theseshortcomings by proposing a new scheduling algorithm that enhanced the combinationalburst time model by using median as a statistics of central tendency and assigning theprocessors to the CPU in interleave order. The proposed algorithm was implemented andcompared with First Come First Serve (FCFS), Longest Job First (LJF), Longest Job Firstwith combinational model (LJF+CBT) and Shortest Job First (SJF) scheduling algorithmsusing varying number of processes and burst times. Results from the experiments showedthat the enhanced LJF+CBT outperformed the existing LJF+CBT producing 26.69% betteraverage waiting time (AWT), 21.77% better average turnaround time (ATAT) and 14.29%better number of context switches (CS). In Longest Job First (LJF) scheduling this algorithmdrastically reduced the average waiting time by 46.5%, average turnaround time by 39.39%and number of context switching between processes by 33.33% for all the number ofprocesses used. Sequel to these results, a better solution to starvation problem in Longest JobFirst scheduling algorithm was proffered.

Get Full Work

Report copyright infringement or plagiarism