CPU scheduling algorithms Criteria in Operating System

What is CPU Scheduling?

CPU scheduling criteria are the rules and performance factors used by an operating system to select the best scheduling algorithm. These criteria help improve how efficiently the CPU executes processes. In other words, they guide the system to make smart decisions about which process should run next. As a result, the system achieves better speed, fairness, and overall performance.

For example, Consider a computer lab where many students use the same system. When multiple programs run at once, the operating system must decide which task gets CPU time first. For example, if one student opens a browser while another runs a program, the system uses scheduling criteria to manage both tasks efficiently. As a result, both users experience smooth performance without major delays. This clearly shows how CPU scheduling criteria improve real-world system efficiency.

CPU scheduling algorithms Criteria

There are different criteria for the CPU scheduling algorithm as follows:-

• CPU utilization: The main purpose of every scheduling algorithm is to keep the CPU busy. The utilization of the CPU can range from 0 to 100. CPU utilization is the percentage of the time interval in which the processor is busy in CPU usage. 
• Throughput: Throughput means the work completed within an interval of time. Based on the duration of processes, throughput may change. It is defined as the number of processes that can be executed per unit of time. For best efficiency, performance should be high. 
• Turnaround time: For an individual process, the main criteria is how long it takes to compute that process. The period from the time of the submission to the time of termination of a process is known as the turnaround time. 
• Waiting time: Once a process initiates execution, the CPU scheduling algorithm does not pretend the time needed to terminate the process. The time spent in the process is waiting to arrive in the ready queue is said to be waiting time.
• Response time: Turnaround time is not the best criteria in the interactive system. A process can generate few outputs fairly quickly and can carry on executing new outcomes during earlier outcomes are being output to the client. Hence, another measure is the duration from the submission of a request till the initial response is generated. 

Diagram of CPU Scheduling Criteria

Figure: CPU Scheduling Criteria

Applications of CPU Scheduling Criteria

1. Operating Systems (Multitasking)

CPU scheduling criteria are widely used in modern operating systems like Windows OS and Linux. These systems handle multiple processes at the same time. Therefore, scheduling criteria ensure smooth multitasking. As a result, users can run multiple applications without delay.

2. Real-Time Systems

In real-time systems, tasks must complete within strict deadlines. CPU scheduling criteria help prioritize critical tasks. This ensures timely execution without failure. Hence, it is essential for systems like medical devices and traffic control.

3. Cloud Computing Systems

Cloud platforms use scheduling criteria to manage multiple users and workloads. Efficient scheduling improves performance and reduces latency. It also ensures fair resource allocation. Therefore, it enhances overall service quality.

4. Batch Processing Systems

In batch systems, large numbers of jobs are processed together. Scheduling criteria help reduce turnaround and waiting time. This improves efficiency and output. As a result, tasks like payroll and report generation run smoothly.

Conclusion

CPU scheduling criteria play a vital role in improving system performance and efficiency. They help balance multiple factors like CPU utilization, waiting time, and fairness. While it may be challenging to satisfy all criteria at once, a well-designed scheduling algorithm ensures optimal results. Therefore, these criteria are essential for building fast, reliable, and user-friendly operating systems.