《操作系统教学资料》2013-CHAP3.pdfVIP

Chapter3 Scheduling(调度) 3.1 Type of Scheduling(调度类型) 3.2 Scheduling Criteria(调度准则) 3.3 Scheduling Strategies(调度策略) 3.4 Terminology(术语) Scheduling (调度) Motivation(调度的动机) Scheduling defines the strategies used to allocate the processor Successful scheduling tries to meet particular objectives such as fast response time, high throughput and high processor efficiency. Scheduling (调度) 3.1 Type of Scheduling(调度类型) Long-term scheduling The long-term scheduler controls the degree of multiprogramming in the system. It determines when a process is allowed to enter the system. Medium-term scheduling The medium-term scheduler is used for process swapping. Short-term scheduling The short-term scheduler of CPU scheduler selects a process from the ready queue and dispatches it. Scheduling (调度) Process State Transitions Scheduling Scheduling (调度) Queuing Diagram for Scheduling Scheduling (调度) 3.2 Scheduling Criteria(调度准则) User Oriented, Performance-Related Criteria: Response time •In an interactive system, this is the time interval between submission of the request (hitting the enter key) and the reception of some response. Turnaround time •For batch jobs, this is the time interval between submission of a process and its completion. Scheduling (调度) 3.2 Scheduling Criteria(调度准则) User Oriented, Performance-Related Criteria: Deadlines •When process deadlines