CPU scheduling algorithm

1. Types of Scheduling

1.1. Long-Term Scheduling

1.2. Medium-Term Scheduling

1.3. Short-Term Scheduling

2. Scheduling Algorithms

2.1. FCFS (First Come First Serve)

2.1.1. Non-preemptive Simple queue-based Convoy effect

2.2. SJF (Shortest Job First)

2.2.1. Non-preemptive & Preemptive (SRTF)

2.2.2. Minimum average waiting time

2.2.3. Problem: Starvation

2.3. Priority Scheduling

2.3.1. Preemptive & Non-preemptive Issue: Starvation → Solution: Aging

2.4. Round Robin (RR)

2.4.1. Preemptive Time quantum (TQ) Fair for all processes High context switching

2.5. Multilevel Queue (MLQ)

2.5.1. Fixed queue assignment Different algorithm per queue No process movement

2.6. Multilevel Feedback Queue (MLFQ)

2.6.1. Dynamic queue shifting Prevents starvation Ideal for mixed workloads

3. Scheduling Criteria

3.1. CPU Utilization

3.2. Throughput

3.3. Turnaround Time = Completion – Arrival

3.4. Waiting Time = Turnaround – Burst

3.5. Response Time = First CPU allocation – Arrival