An Improved and Performance Evaluation of a New Shortest Round First (SRF) based Scheduling Algorithm Considering with Quantum Time

: CPU scheduling is the most primary and basic function of computer’s operating system. This is very essential for execution of every program. CPU scheduling is a mechanism by which the CPU of a computer is kept busy. According to CPU scheduling our paper focuses about the shortest round first based scheduling algorithm with quantum time which compare to First come first serve(FCFS), Shortest job first,(SJF), Round Robin(RR). According to our new scheduling algorithm gives us better result than the others scheduling.


INTRODUCTION:
The operating system is the most important program that runs on a computer to run other programs and applications. For the management of handling multiple applications of a PC. The CPU must have a useful way of using CPU scheduling. Mainly Operating system is to provide as a good environment where user can execute program with efficient manner.

CPU
scheduling: CPU scheduling operates this multiprogramming task by switching one after another. There must be a way for the operating system and application processes to share the CPU.
CPU scheduler: It means amount of the time the CPU is takes for executing instruction of processes. Scheduler can select a process among the processes that are ready to execute and allocates CPU to one of them.
Dispatcher: Dispatcher function is essential for CPU scheduling because it controls the process by short term scheduler. The dispatcher should be as fast as possible so that it can switch programs.
Scheduling criteria: The criteria include with the following topics. CPU utilization: Generally the CPU should keep busy 100% of time so that CPU cycle does not get wasted. But actually CPU usage range is 40 percent for light load and 90 percent for heavy load.
Throughput: Throughput is known for number of process that takes to finish of execution per unit time. May range from 10/second to 1/hour depending on the special task. 4. Proposed methodology: Operating system provides CPU scheduling to give a scheduling for every process in ready queue. According to the CPU scheduling algorithm its allows minimizing of waiting time, turnaround time and response time and optimum consentient high throughput. There are different type of scheduling algorithms are available in operating system such as First come first served(FCFS), Shortest job first(SJF), priority scheduling, Round robin(RR). The FCFS is the simplest CPU algorithm and it is easy to implement. It does not provide the best service. SJF (Shortest job first) scheduling provides the shortest process priority. RR (Round Robin) is one of the most popular scheduling results in average turnaround time and average waiting time. Our paper gives batter result then others scheduling algorithms.
Proposed SRF CPU scheduling algorithm: Step 1: Taking processes.
Step 2: Enter the arrival time and burst time of processes in ready queue.
Step 3: If any process arrival time comes then enter the process in the ready queue and do step 4.
Step 4: Present all the processes in the ready queue in ascending order by using their burst time. Step 5: If the process available in the ready queue then taking first ascending order shortest process from the ready queue and do step 6 otherwise do step 7.
Step 6: Process burst time> quantum time if the condition is true then allocate the CPU to it for a time interval of up to quantum and set => process burst time=remaining burst time and do step 3, 4 and 5. If the condition is false then allocates the CPU to the currently running process and removed it from the ready queue and do step 3, 4,5.
Step 7: If the ready queue is empty then finish. Shortest job first (SJF) Scheduling: The SJF algorithm is essential to pick the fastest small job that needs to be done as quickly as possible and then pick the next smallest fastest job to do next. This algorithm picks a process depending on the next shortest CPU burst. Paper Analysis: If we see the following chart than we can understand the compare of our scheduling with others scheduling algorithm. Here, the ( Fig.1) shown that average waiting time of SRF is 3 and average turnaround time is 7. The average waiting time of RR is 4.5 and average turnaround time is 8.5. The average waiting time of SJF is 4 and average turnaround time is 8. The average waiting time of PS is 4 and average turnaround time is 8. The average waiting time of FCFS is 4.75 and average turnaround time is 8.75. So, our scheduling algorithm gives better result than others scheduling algorithms.

CONCLUSION
In this study we proposed an improved and performance evaluation of a new Shortest Round First (SRF) based scheduling algorithm considering with quantum time for operating system. SRF scheduling algorithm shows that better performance and effectiveness compare with another scheduling. According to Shortest Round First gives better Average Waiting Time and Average Turnaround Time.