tailieunhanh - Lecture Operating system concepts - Module 5

In this chapter, you will learn to: To describe the basic organization of computer systems, to provide a grand tour of the major components of operating systems, to give an overview of the many types of computing environments, to explore several open-source operating systems. | Module 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Algorithm Evaluation Operating System Concepts Basic Concepts Maximum CPU utilization obtained with multiprogramming CPU–I/O Burst Cycle – Process execution consists of a cycle of CPU execution and I/O wait. CPU burst distribution Operating System Concepts Alternating Sequence of CPU And I/O Bursts Operating System Concepts Histogram of CPU-burst Times Operating System Concepts CPU Scheduler Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1. Switches from running to waiting state. 2. Switches from running to ready state. 3. Switches from waiting to ready. 4. Terminates. Scheduling under 1 and 4 is nonpreemptive. All other scheduling is preemptive. Operating System Concepts Dispatcher Dispatcher module gives control of the CPU to the process | Module 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Algorithm Evaluation Operating System Concepts Basic Concepts Maximum CPU utilization obtained with multiprogramming CPU–I/O Burst Cycle – Process execution consists of a cycle of CPU execution and I/O wait. CPU burst distribution Operating System Concepts Alternating Sequence of CPU And I/O Bursts Operating System Concepts Histogram of CPU-burst Times Operating System Concepts CPU Scheduler Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1. Switches from running to waiting state. 2. Switches from running to ready state. 3. Switches from waiting to ready. 4. Terminates. Scheduling under 1 and 4 is nonpreemptive. All other scheduling is preemptive. Operating System Concepts Dispatcher Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: switching context switching to user mode jumping to the proper location in the user program to restart that program Dispatch latency – time it takes for the dispatcher to stop one process and start another running. Operating System Concepts Scheduling Criteria CPU utilization – keep the CPU as busy as possible Throughput – # of processes that complete their execution per time unit Turnaround time – amount of time to execute a particular process Waiting time – amount of time a process has been waiting in the ready queue Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment) Operating System Concepts Optimization Criteria Max CPU utilization Max throughput Min turnaround time Min waiting time Min response time Operating System Concepts First-Come, First-Served (FCFS) Scheduling Example: Process Burst Time P1 24 P2 3 P3 3 Suppose that the