You Are Requested To Evaluate The Following Scheduling Algor ✓ Solved

You Are Requested To Evaluate The Following Scheduling Algorithms And

Evaluate the following scheduling algorithms and identify which could lead to starvation. Explain the reasons behind potential starvation by providing specific scenarios that might cause it:

• First-come, first-served
• Shortest job first
• Round robin
• Priority

Additionally, discuss how semaphores can be used by a server to control the number of accepted connections, given that the server can handle only N connections at once. Explain how the acquire() and release() methods facilitate this control.

Finally, analyze the consequences of not executing wait() and signal() semaphore operations atomically in terms of mutual exclusion. Provide an example where multiple processes invoke wait() concurrently without atomic execution, leading to potential issues.

Sample Paper For Above instruction

Introduction

Scheduling algorithms are essential components of operating systems, determining how processes are allocated CPU time. Each algorithm has unique characteristics that influence system performance, fairness, and potential issues like starvation. Moreover, synchronization mechanisms like semaphores are vital for managing shared resources such as server connections. Understanding how these mechanisms function and their pitfalls is critical for system stability.

Evaluation of Scheduling Algorithms and Starvation Scenarios

First-come, first-served (FCFS)

The FCFS scheduling algorithm processes tasks in the order of arrival. While straightforward, it can lead to the problem of starvation for shorter processes, especially if long processes arrive early. For example, if a long process keeps arriving before shorter processes, the shorter processes may wait indefinitely, exemplifying starvation. This scenario is known as the "convoy effect," where short processes are delayed behind longer ones, causing unfairness.

Shortest job first (SJF)

SJF schedules processes based on the estimated execution time, prioritizing shorter tasks. Although efficient in reducing average wait time, it can cause starvation of longer processes if shorter processes continually arrive. For instance, if an constantly arriving stream of short processes prevents longer processes from executing, the longer processes may starve indefinitely, leading to unfairness and potential system bottlenecks.

Round robin (RR)

Round robin scheduling assigns fixed time slices to processes in a cyclic order. Its fairness ensures no process indefinitely monopolizes the CPU. However, starvation can occur if a process consistently receives very short time slices or if processes frequently re-enter the queue without being granted CPU time. For example, in a system with high process priority variability, lower-priority processes may suffer from starvation if higher-priority processes preempt them continuously.

Priority Scheduling

Priority scheduling selects processes based on priority levels. While it improves system responsiveness for high-priority tasks, it can cause starvation of low-priority processes if high-priority processes continually arrive. For example, a low-priority background process might never execute if high-priority processes keep incoming, leading to starvation and system inefficiency for certain processes.

Using Semaphores to Control Server Connections

Semaphores are synchronization tools that can effectively limit the number of active connections a server handles at any given time. Suppose a server has a maximum of N socket connections. A semaphore initialized with the value N can be used to enforce this limit. When an incoming connection is received, the server invokes the acquire() method. If the semaphore's value is greater than zero, acquire() decrements it and allows the connection. If not, the server blocks the incoming connection until an existing connection releases the semaphore by invoking release(). This mechanism ensures that the server never exceeds its connection limit, maintaining resource stability and preventing overload.

Consequences of Non-Atomic Semaphore Operations

If wait() and signal() operations are not executed atomically, race conditions can arise, compromising mutual exclusion. For example, consider multiple processes attempting to enter a critical section protected by a semaphore. If process A executes wait(), but before it decrements the semaphore value, process B also executes wait(), both processes might believe they have acquired the lock simultaneously, leading to interference and inconsistent data states. Such non-atomic execution allows multiple processes to access critical resources concurrently, violating mutual exclusion principles and risking system inconsistency or crashes.

Conclusion

In summary, selecting appropriate scheduling algorithms is crucial to balance efficiency and fairness while avoiding starvation. Understanding how to employ semaphores for resource management is vital for robust system design. Ensuring atomicity in semaphore operations is essential to preserve mutual exclusion and system integrity, especially in concurrent processing environments.

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