Consider The Mix Of Jobs With Parameters Described In Table

consider the mix of jobs with parameters described in Table 1

Consider the mix of jobs with parameters described in Table 1. Assume that ties (if any) are broken by scheduling jobs with lower ID first.

Compute the following: a) The schedule produced by SRT. Try to use the same notation as in the lecture notes. b) The schedule produced by HSN. Try to use the same notation as in the lecture notes. c) The schedule produced by SJN. Try to use the same notation as in the lecture notes. d) Which algorithm achieves better performance in terms of average response time? Motivate your answer. e) Which algorithm achieves better fairness? Motivate your answer.

Paper For Above instruction

In the realm of operating systems, job scheduling algorithms are pivotal in ensuring efficiency and fairness in process execution. This paper delves into three specific algorithms—Shortest Remaining Time (SRT), Highest Seniority (HSN), and Shortest Job Next (SJN)—analyzing their scheduling sequences, performance metrics, and fairness levels based on a given set of job parameters.

Analysis of Job Scheduling Algorithms

The given scenario involves a set of jobs with specific attributes such as Job ID, Job Length, and Arrival Time. Although the exact parameters are not provided here, typical scheduling sequence analysis involves understanding how each algorithm prioritizes jobs based on their attributes.

Schedule Produced by SRT

The Shortest Remaining Time (SRT) algorithm, a preemptive version of Shortest Job First, always picks the process with the minimal remaining processing time. This approach minimizes average response and turnaround time by promptly executing shorter jobs, preempting longer jobs if necessary. Given the job parameters, the schedule generated by SRT would dynamically switch between jobs, always selecting the job with the least remaining execution time at each moment. The notation used in lecture notes typically includes a Gantt chart illustrating job execution intervals, with preemptions marked explicitly. For example, if Job 2 arrives while Job 1 is executing but has a shorter remaining time, the CPU would preempt Job 1 to process Job 2. Repeated preemptions result in a schedule skewed toward shorter jobs, enhancing efficiency but potentially affecting fairness.

Schedule Produced by HSN

The Highest Seniority or HSN scheduling policy favors jobs with lower Job IDs, breaking ties by order of arrival or other criteria as outlined in the lecture notes. This non-preemptive algorithm processes jobs based on their static priority or seniority. Under HSN, once a job starts executing, it runs to completion unless explicitly interrupted by higher priority criteria (if preemption is permitted). The schedule would sequentially process jobs starting from the one with the lowest Job ID that has arrived, emphasizing fairness based on job age or identifier rather than dynamic metrics like remaining time. The resulting schedule might favor longer jobs with higher IDs if they arrived earlier, leading to potentially longer response times for short jobs arriving later.

Schedule Produced by SJN

The Shortest Job Next (SJN), also known as Shortest Job First (SJF), is a non-preemptive policy that always selects the job with the shortest total processing time among all waiting jobs. This policy aims to minimize average turnaround time but can cause longer jobs to experience starvation if shorter jobs continually arrive. The schedule under SJN is constructed by selecting the shortest available job at each step, ensuring that the shortest jobs are executed first. The notation in lecture notes includes a series of execution intervals ordered by increasing job length, with waiting times depending on the order of arrival and job lengths.

Comparison of Performance and Fairness

In terms of performance, specifically average response time, SRT typically outperforms the others by preemptively executing the shortest remaining processes, minimizing waiting times for short jobs. SJN also yields a low average response time in theory but can suffer from starvation issues without mechanisms like aging. HSN, prioritizing job ID or seniority, may have higher average response times but ensures fairness based on job age. Regarding fairness, HSN is generally more equitable because it processes jobs in a fixed order based on their identifiers or seniority, preventing starvation. SRT and SJN, due to their focus on minimizing average response time, can disproportionately favor short jobs, leading to potential starvation of longer jobs and thus less fairness.

Conclusion

In conclusion, the selection among these algorithms depends on the desired balance between efficiency and fairness. SRT excels in reducing average response time but may lead to starvation and unfairness toward longer jobs. HSN emphasizes fairness, giving priority based on static job attributes, at the expense of higher average response time. SJN offers a compromise, often yielding low response times but requiring mechanisms to prevent starvation. The detailed analysis underscores the importance of context and workload characteristics in selecting an appropriate scheduling policy.

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