2.12 || CPU scheduling Decision || Operating system || #operatingsystem

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CPU Scheduling Decisions in Operating Systems

Description:
CPU scheduling decisions in operating systems involve selecting the most suitable process to allocate CPU time, ensuring efficient utilization of the CPU and fair execution of processes. These decisions are made based on various scheduling algorithms and policies implemented by the operating system.

When making CPU scheduling decisions, the operating system considers factors such as process priority, process state, available resources, and scheduling algorithm characteristics. Here are some commonly used CPU scheduling decisions:

1. Process Selection: The operating system determines which process from the ready queue should be allocated CPU time. It can be based on different criteria, such as process priority, process arrival time, process burst time, or a combination of these factors. The selected process is typically the one with the highest priority or the shortest remaining execution time.

2. Preemptive vs. Non-preemptive: The decision whether to allow preemption, i.e., interrupting a running process and allocating the CPU to a higher-priority process, depends on the scheduling policy. Preemptive scheduling allows for better responsiveness and priority handling but incurs additional overhead due to context switches. Non-preemptive scheduling ensures each process completes its execution or voluntarily yields the CPU before another process is selected.

3. Time Quantum: In time-sliced scheduling algorithms like Round-Robin (RR), the operating system determines the time quantum or time slice assigned to each process. The time quantum represents the maximum amount of time a process can execute before being preempted and moved to the end of the ready queue. The choice of an appropriate time quantum affects the trade-off between fairness and system responsiveness.

4. Aging and Priority Adjustment: Some scheduling policies incorporate aging mechanisms to adjust process priorities over time. Aging increases the priority of long-waiting processes to prevent starvation and ensure fair access to CPU resources. The operating system may dynamically adjust process priorities based on factors like waiting time, resource usage, or feedback from the system state.

5. Scheduling Algorithm Evaluation: The operating system periodically evaluates the performance of the current scheduling algorithm and may decide to switch to a different algorithm based on system metrics, such as average waiting time, throughput, or response time. The choice of a suitable scheduling algorithm depends on the specific requirements of the system and the workload characteristics.

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