Comparison of Different Approaches to Scheduling
The Role of Scheduling in Operating Systems
Definition
Scheduling
Scheduling is the process of allocating CPU time to various processes to optimize system performance.
It ensures that critical tasks are completed efficiently while maintaining fairness among all processes.Note
Scheduling is essential for managing multitasking environments, where multiple processes compete for limited resources.
Key Metrics for Evaluating Scheduling Algorithms
- Throughput: The number of processes completed in a given time period.
- Turnaround Time: The total time taken for a process to complete, from arrival to termination.
- Waiting Time: The time a process spends in the ready queue before execution.
- CPU Utilization: The percentage of time the CPU is actively executing processes.
Ineffective scheduling can lead to issues like high latency, low throughput, and poor CPU utilization.
First-Come, First-Served (FCFS)
Definition
First-Come, First-Served (FCFS)
Processes are executed in the order they arrive, with no pre-emption.
Characteristics:
- Non-Preemptive: Once a process starts, it runs to completion.
- Simple: Easy to implement and understand.
FCFS can lead to the convoy effect, where short processes are delayed by long ones, reducing overall efficiency.
Round Robin
Definition
Round Robin
Each process receives a fixed time slice (quantum) in a cyclic order.
Characteristics:
- Preemptive: Processes are interrupted if they exceed their time quantum.
- Fair: Ensures all processes receive equal CPU time.
- Choosing the right time quantum is critical.
- Too short a quantum increases context switching overhead, while too long makes it resemble FCFS.
