CPUplanning

CPUplanning, sometimes referred to as CPU scheduling, is the subsystem of an operating system that decides which process or thread receives the central processing unit at any moment. Its goal is to optimize the use of the CPU while balancing performance, responsiveness, and fairness across running tasks.

Decisions in CPUplanning can be preemptive or non-preemptive. In non-preemptive schemes, a running process continues until it blocks, terminates, or yields the CPU. In preemptive schemes, the scheduler can suspend a running process to allocate the CPU to another task, enabling better responsiveness and multicore utilization but increasing context-switch overhead.

Common CPU planning algorithms include first-come, first-served (FCFS); shortest job first (SJF) and its preemptive variant (SRTF); priority-based scheduling; round-robin (RR); and multilevel feedback queues. Real-time systems may employ policies such as Rate Monotonic or Earliest Deadline First to meet hard deadlines. Each algorithm presents different trade-offs among throughput, average waiting time, turnaround time, response time, and fairness. Aging techniques can mitigate starvation by gradually increasing the priority of waiting tasks.

In practice, CPUplanning must handle diverse workloads, including CPU-bound and I/O-bound processes, as well as context-switch costs. Modern operating systems often implement sophisticated schedulers that adapt to multiprocessor or multi-core environments, leveraging affinities, load balancing, and quality-of-service requirements to optimize overall system performance. Related concepts include thread scheduling, process management, and real-time scheduling.