Uniprocessor Scheduling
Chapter 9
CS 431 -- Operating Systems
Dr. Tim McGuire
Sam Houston State University


CPU Scheduling

Classification of Scheduling Activity Queuing Diagram for Scheduling
        Figure 9.3

Long-Term Scheduling

Medium-Term Scheduling Short-Term Scheduling Short-Tem Scheduling Criteria Priorities Characterization of Scheduling Policies The CPU-I/O Cycle Our running example to discuss various scheduling policies
 
Process
Arrival Time
Service Time
1
0
3
2
2
6
3
4
4
4
6
5
5
8
2
Service time = total processor time needed in one (CPU-I/O) cycle
Jobs with long service time are CPU-bound jobs and are referred to as “long jobs”


First Come First Served (FCFS)

FCFS drawbacks Round-Robin Time Quantum for Round Robin Round Robin: critique Queuing for Virtual Round Robin
            Figure 9.7

Shortest Process Next (SPN)

Estimating the required CPU burst Exponentially Decreasing Coefficients
            Figure 9.8
            Figure 9.9a Shortest Process Next: critique Multilevel Feedback Scheduling Multiple Feedback Queues Time Quantum for Feedback Scheduling Algorithm Comparison Fair Share Scheduling The Fair Share Scheduler (FSS)