CPU Scheduling Policies: FIFO, SJF, and Round Robin

This lecture discusses various CPU scheduling policies, focusing on First In, First Out (FIFO), Shortest Job First (SJF), and Round Robin (RR). It begins by outlining simplifying assumptions for scheduling, such as jobs running for the same duration and arriving simultaneously. The instructor illustrates FIFO with examples, highlighting its average turnaround time and the convoy effect, where long jobs delay shorter ones. The lecture then introduces SJF, demonstrating its efficiency in reducing turnaround time compared to FIFO. The discussion progresses to Shortest Time to Completion First (STCF), which allows preemption, improving turnaround times further. The importance of response time is emphasized, particularly in interactive systems, contrasting it with turnaround time. Finally, the lecture covers Round Robin scheduling, explaining its time-slicing approach and the trade-offs between response time and turnaround time. The instructor concludes by noting the practical applications of these scheduling policies in modern operating systems, setting the stage for future discussions on incorporating I/O into scheduling.