timeslicing

Timeslicing, also known as time slicing, is a CPU scheduling technique in which the available processing time is divided into small, fixed-length intervals called time slices or quanta. The operating system’s scheduler allocates each ready process a slice in turn. When a process uses up its slice, a context switch occurs and the CPU is given to the next process, enabling multiple tasks to share CPU time.

This preemptive multitasking approach aims to improve responsiveness in interactive and multi-user systems by preventing any single process from monopolizing the processor. The length of the time slice, or quantum, is a key parameter: short quanta improve system responsiveness and UI feel but increase the overhead from more frequent context switches; longer quanta reduce switching overhead but can lead to longer wait times for other tasks and decreased interactivity.

Implementation typically relies on a timer interrupt to enforce preemption. The system maintains a ready queue of processes and selects the next candidate according to a scheduling policy, commonly round-robin or a priority-based scheme with per-task quanta. Some systems employ aging to prevent starvation, gradually increasing a waiting task’s priority. In real-time environments, time slicing may be minimized or disabled for high-priority tasks to meet timing requirements.

History and scope: timeslicing emerged with early time-sharing and multi-user systems in the 1960s and 1970s and remains a foundational concept in operating system design. Modern general-purpose schedulers often use more sophisticated policies, but the basic idea of dividing CPU time into slices to share compute resources continues to influence contemporary scheduling strategies in desktops, servers, and embedded systems.