Algoritma Penjadwalan Sistem Operasi - FCFS & SJF

Introduction

This tutorial provides a comprehensive overview of CPU scheduling algorithms, specifically focusing on First Come, First Served (FCFS) and Shortest Job First (SJF). Understanding these algorithms is crucial for optimizing process management in operating systems, as they determine how processes are allocated CPU time.

Step 1: Understanding CPU Scheduling

• CPU scheduling is the method by which processes are assigned to the CPU.
• It involves selecting which process from the ready queue will be executed next.
• Effective scheduling is vital for maximizing CPU utilization and minimizing waiting time.

Step 2: First Come, First Served Algorithm

• FCFS is the simplest CPU scheduling algorithm.
• Processes are executed in the order they arrive in the ready queue.

Characteristics of FCFS

• Non-preemptive: Once a process starts executing, it cannot be interrupted until completion.
• Fairness: Each process gets a chance to execute based on arrival time.

Advantages of FCFS

• Simple to understand and implement.
• No starvation occurs; every process will eventually be executed.

Disadvantages of FCFS

• Can lead to the "convoy effect," where shorter processes wait for longer ones, increasing overall waiting time.

Step 3: Shortest Job First Algorithm

• SJF selects the process with the smallest execution time from the ready queue.

Characteristics of SJF

• Can be either preemptive or non-preemptive.
• It aims to minimize the average waiting time for processes.

Advantages of SJF

• Generally provides better average waiting time and turnaround time compared to FCFS.

Disadvantages of SJF

• Difficult to predict execution time for processes.
• Potential for starvation, where longer processes may wait indefinitely if shorter ones keep arriving.

Step 4: Comparing FCFS and SJF

• FCFS is simpler and fairer but can be inefficient for process execution time.
• SJF optimizes waiting time but may lead to unfairness if not managed properly.

Practical Application

• Use FCFS for simple systems where processes have similar execution times.
• Consider SJF for environments with a mix of short and long processes, but implement measures to prevent starvation.

Conclusion

In summary, FCFS and SJF are fundamental CPU scheduling algorithms with distinct advantages and disadvantages. FCFS is straightforward and fair, while SJF is efficient but requires careful management to avoid starvation. Understanding these algorithms will help in making informed decisions about process scheduling in operating systems. For further exploration, consider experimenting with these algorithms through simulations or practical implementations in programming environments.