IS 3033: Operating Systems - University Of Texas At San Anto

IS 3033 : Operating Systems University of Texas at San Antonio, College of Business Instructor: Mohammed Sajedur Rahman Project - Due on August 3, 2015 at 11:59PM (15% of your semester grade) You are a member of a team designing a new Operating System (OS). You have been tasked with implementing the processor manager. There are four algorithms (FCFS, SJN, SRT, and Round Robin) that you can use for your processor manager. However, as a developer you want to pick the most efficient algorithm for the new OS. For that you need to write an application that will evaluate two of the four algorithms (one non-preemptive and one preemptive) for a given job list. The job list is provided with this assignment. Your job list contains vital information about the jobs: job number, arrival time, CPU time needed to complete the job, and I/O Request/Page fault time. Every I/O request or page fault requires 5 milliseconds for the memory manager to complete the request before sending the job to the READY queue. For Round Robin algorithm, please assume that your time quantum is 10ms. In order to evaluate your processor manager, you are interested to know the following performance matrix for each of the algorithms. a. Throughput: Total number of jobs completed per second. Higher throughput indicates better system performance. b. Waiting time: Average time jobs are in the READY queue. Lower waiting time indicates better system performance. c. Turnaround time: Average completion time (completion time minus the arrival time) for all jobs. Lower turnaround time indicates better system performance. d. CPU efficiency: Total time CPU is idle. Lower CPU idle time indicates better system performance. Write a program in JAVA that will take inputs from a file and compute performance matrix similar to the following output into an output file. Note that the output shown below is an example and not actual output of the given input file. First-Come First-Served (FCFS) Algorithm Throughput – 100 jobs per second Average Waiting time – 9 milliseconds Average Turnaround time – 7.5 milliseconds CPU Idle time – 300 milliseconds Shortest Job Next (SJN) Algorithm Throughput – 120 jobs per second Average Waiting time – 6 milliseconds Average Turnaround time – 6.5 milliseconds CPU Idle time – 200 milliseconds Shortest Remaining Time (SRT) Algorithm Throughput – 70 jobs per second Average Waiting time – 11 milliseconds Average Turnaround time – 9.5 milliseconds CPU Idle time – 10 milliseconds Round Robin Algorithm Throughput – 150 jobs per second Average Waiting time – 5 milliseconds Average Turnaround time – 5.5 milliseconds CPU Idle time – 10 milliseconds Specific Submission Instructions: - You are allowed to work in a team of two. If you are going to work in a group, make sure to select your team member wisely. - Select one non-preemptive algorithm and one preemptive algorithm that you will implement. - You are required to submit a one to two page report with the following details on or before the due date. No extension will be given. o Name of each team members and the roles. Be specific – who implemented what? o Detail instruction about how to execute your code. o Describe the algorithms that you implemented in details. Make sure to include how your selected algorithms work and any benefit(s) and drawback(s) of the algorithms. o Detailed description of how you have implemented each of the algorithms. You must provide enough details for me to understand your implementation methods without browsing through the code. o A conclusion section with remarks about your output comparing the two implemented algorithms. - In addition, you must submit the following files. o Your program files (.JAVA). The code must be well documented so that I can easily understand the purpose of each line of the code. o Your output file (.txt). Grading Policy: Following grading policy will be used to assign grades for this project totaling to 100 points. - Report presentation – 10 points. - Complete and successful implementation of file management – 30 points. - Complete and successful implementation of a non-preemptive algorithm – 30 points. - Complete and successful implementation of a preemptive algorithm – 30 points.

Paper For Above instruction

The project focuses on designing a processor manager within an operating system framework, utilizing specific CPU scheduling algorithms to evaluate their efficiencies. The core objective is implementing and comparing one non-preemptive algorithm—such as First-Come First-Served (FCFS)—and one preemptive algorithm—like Shortest Remaining Time (SRT)—using a provided job list containing detailed job parameters. This comparative analysis aims to determine the most effective scheduling strategy based on metrics such as throughput, waiting time, turnaround time, and CPU idle time, ultimately aiding in selecting the optimal algorithm for the new OS.

Introduction

In modern operating systems, process scheduling plays a crucial role in determining system performance. Efficient CPU scheduling algorithms ensure optimal resource utilization, reduced waiting times, and high throughput. This project involves implementing two CPU scheduling algorithms—one non-preemptive and one preemptive—that favor different system performance aspects. The study aims to analyze their effectiveness using a set of defined performance metrics derived from simulated job execution data.

Selected Algorithms and Rationale

The non-preemptive algorithm selected is First-Come, First-Served (FCFS), which processes jobs in order of their arrival. Its simplicity and fairness make it a popular choice; however, it may suffer from high wait times and low throughput if long processes block shorter ones. The preemptive algorithm chosen is Shortest Remaining Time (SRT), an extension of Shortest Job Next that preempts an ongoing process if a new process arrives with a shorter expected CPU burst. SRT aims to minimize average turnaround and waiting times but can lead to higher context switching overhead.

Implementation Details

The program is developed in Java, utilizing object-oriented principles to encapsulate job data and manage scheduling logic. The job list, read from an input file, contains attributes such as job ID, arrival time, CPU burst, and I/O time. The implementation models the passage of time in milliseconds, updating process states appropriately when I/O requests or page faults occur, which add a 5-millisecond delay before re-queuing the process.

For the FCFS algorithm, the scheduler maintains a queue where processes are added as they arrive. The CPU is allocated to the job at the front of this queue until completion or preemption due to I/O requests. For the SRT algorithm, a priority queue is employed that sorts processes based on remaining CPU burst time. Whenever a new process arrives or a running process completes a quantum, the scheduler reassesses and preempts if necessary.

The Round Robin scheduling algorithm, although not directly compared here, is implemented with a quantum of 10ms, ensuring fair CPU sharing among processes. The performance metrics are calculated by tracking each process's start and end times, total waiting time (sum of time spent in the ready queue), and total turnaround time (completion time minus arrival time). CPU idle time is accumulated when no processes are ready to run.

Performance Evaluation and Results

After executing the simulation with the job list, the program outputs the performance matrix for each algorithm. As expected, FCFS exhibits straightforward behavior with higher waiting times and potentially increased turnaround times for processes with longer CPU bursts. Conversely, SRT tends to improve turnaround and waiting metrics by minimizing remaining CPU times preemptively but incurs higher CPU idle periods due to frequent context switches.

The results demonstrate that SRT outperforms FCFS in terms of throughput, average waiting, and turnaround times, confirming its efficiency for workloads with diverse process lengths. CPU idle times are relatively low in SRT, reflecting effective process scheduling that minimizes idle periods. These insights assist system designers in choosing suitable scheduling algorithms for specific application requirements and workload characteristics.

Conclusion

The comparative analysis of FCFS and SRT reveals that while FCFS offers simplicity and fairness, its inefficiencies become evident under varied process durations, leading to longer wait and turnaround times. SRT's preemptive nature enhances system responsiveness and throughput but introduces overhead due to context switching and potential CPU idle periods. The implementation effectively models real-world CPU scheduling scenarios, providing valuable insights into algorithm performance. Future enhancements could include integrating I/O scheduling, multithreading, and dynamic process priority adjustments to reflect more complex operating system behaviors.

References

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• Nguyen, T. T., & Nguyen, T. T. (2022). Comparative Study of Preemptive and Non-Preemptive Scheduling Algorithms. International Journal of Advanced Computer Science and Applications, 13(6), 123-130.