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CPU scheduling is the basis of multi
programmed operating system. By switching among various processes OS makes the
system more productive CPU scheduling algorithm have various properties for
choice of particular algorithm that which algorithm to use in which situation.
Many criteria have been suggested for comparing these algorithms. Certain
characteristics are used for comparison can make substantial difference in
which algorithm is judged to be best. In this term report a newly proposed CPU
Scheduling algorithm named Shortest Job Round Robin with existing algorithms is
reviewed, analysed and observed that which scheduling properties are satisfied
by this algorithm. It is quite optimal in scheduling than all other CPU
scheduling algorithms in case of AWT and TAT but still have context switching
overhead but fair in scheduling.

 

Keywords— Shortest
Job First, Shortest Remaining Time Next, Highest Response Ratio Next,
Throughput, Dispatch Time, Arrival Time.

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I.     
Introduction

 

Operating system performs variety of
tasks in which scheduling is one of the basic task. All the resources of the
computer are scheduled before use; as CPU is one of the major computer
resources therefore scheduling is vital for operating system 4. Scheduling is
a technique which involves complex set of policies and mechanisms working at
back of processor, instructing it the order in which it should execute a given
set of processes 5. CPU scheduling is the basis of multi programmed operating
systems. By switching the CPU among processes, the operating system can make
the computer more productive 2.

 

When a computer is multi programmed, it
frequently has multiple processes competing for the CPU at the same time. This
situation occurs whenever two or more processes are simultaneously in the ready
state. If only one CPU is available, a choice has to make which process to run
next. The part of the operating system that makes the choice is called
scheduler and the algorithm it uses is called scheduling algorithm 3.

In a single processor system, only one
process can run at a time; any others must wait until the CPU is free and can
be rescheduled 2. The success of CPU scheduling depends on an observed
property of processes: process execution consists of a cycle of CPU execution
and I/O wait. Processes alternate between these two states. Processor execution
begins with a CPU burst. That is followed by an I/O burst, Which is followed by
another CPU burst, then another I/O burst and so on2. This article
constitutes the following sections. Section 2 have an overview of some
scheduling criteria on the basis of these algorithm is evaluated in rest of the
sections. Section 3 introduces existing scheduling algorithms. Section 4 has a
quick overview of SJRR its working logic and review of related sections of
paper. Section 5 contains analysis based on experimental results followed by
conclusion.

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