CPU scheduling is the basis of multiprogrammed operating system. By switching among various processes OS makes thesystem more productive CPU scheduling algorithm have various properties forchoice of particular algorithm that which algorithm to use in which situation.Many criteria have been suggested for comparing these algorithms. Certaincharacteristics are used for comparison can make substantial difference inwhich algorithm is judged to be best.
In this term report a newly proposed CPUScheduling algorithm named Shortest Job Round Robin with existing algorithms isreviewed, analysed and observed that which scheduling properties are satisfiedby this algorithm. It is quite optimal in scheduling than all other CPUscheduling algorithms in case of AWT and TAT but still have context switchingoverhead but fair in scheduling. Keywords— ShortestJob First, Shortest Remaining Time Next, Highest Response Ratio Next,Throughput, Dispatch Time, Arrival Time.I. Introduction Operating system performs variety oftasks in which scheduling is one of the basic task. All the resources of thecomputer are scheduled before use; as CPU is one of the major computerresources therefore scheduling is vital for operating system 4. Scheduling isa technique which involves complex set of policies and mechanisms working atback of processor, instructing it the order in which it should execute a givenset of processes 5.
CPU scheduling is the basis of multi programmed operatingsystems. By switching the CPU among processes, the operating system can makethe computer more productive 2. When a computer is multi programmed, itfrequently has multiple processes competing for the CPU at the same time. Thissituation occurs whenever two or more processes are simultaneously in the readystate. If only one CPU is available, a choice has to make which process to runnext. The part of the operating system that makes the choice is calledscheduler and the algorithm it uses is called scheduling algorithm 3.In a single processor system, only oneprocess can run at a time; any others must wait until the CPU is free and canbe rescheduled 2. The success of CPU scheduling depends on an observedproperty of processes: process execution consists of a cycle of CPU executionand I/O wait.
Processes alternate between these two states. Processor executionbegins with a CPU burst. That is followed by an I/O burst, Which is followed byanother CPU burst, then another I/O burst and so on2. This articleconstitutes the following sections. Section 2 have an overview of somescheduling criteria on the basis of these algorithm is evaluated in rest of thesections. Section 3 introduces existing scheduling algorithms. Section 4 has aquick overview of SJRR its working logic and review of related sections ofpaper.
Section 5 contains analysis based on experimental results followed byconclusion.