William Stallings Computer Organization and Architecture

1. William Stallings Computer Organization and Architecture Chapter 7 Operating System Support 操作系统支持 Original Author:Adrian J Pullin Adapted by: Yanru Bao, Tianjin University

2. Topics • Overview 概述 • Scheduling 调度 • Memory Management 内存管理 • Pentium II and PowerPC Memory Management Pentium II 和 PowerPC 的内存管理

3. Overview • What is an OS? The operating system is a program that manages the computer’s resources, provides services for programmers, and schedules the execution of other programs.操作系统是负责管理计算机资源、为程序员提供服务、对其他程序的执行进行调度的软件

4. Overview • Objectives and Functions (OS的目标和功能) • Convenience 方便性 • Making the computer easier to use 使计算机更加容易使用 • Efficiency 有效性 • Allowing better use of computer resources 使计算机资源得到更加有效的利用

5. The Operating System as a User/Computer Interface Layers and Views of a Computer System

6. Operating System Services (1) • Program creation 程序的建立 • provides a variety of facilities and services to assist in creating programs, such as editors and debuggers • 为用户进行编程时提供各种工具和服务， 如：编辑程序、调试程序 • Program execution 程序执行 • a number of tasks need to be performed to execute a program • 执行一个程序需要完成许多任务

7. Operating System Services (2) • Access to I/O devices 访问I/O设备 • each I/O device requires its own peculiar set of instructions or control signals for operation • 每一个I/O设备都需要自己特有的指令集以及控制信号以进行操作 • Controll access to files 控制文件存取 • control include an understanding the nature of the I/O device and the file format • 控制包括对I/O设备的性质以及文件格式的理解

8. Operating System Services (3) • System access 系统访问 • OS control access to the system as a whole and to specific system resources • OS对系统整体以及特殊的系统资源进行访问控制 • resolve conflicts for resource contention • 解决资源竞争冲突

9. Operating System Services (4) • Error detection and response 错误检查和响应 • OS make response OS对错误能够作出响应 • ending the program, retrying the operation, reporting the error • OS能够终止出错程序、重试操作、报告错误 • Accounting 统计 • Collect usage statistics for various resources • 能够对各种资源的使用情况进行统计

10. O/S as a Resource Manager(1) • A computer is a set of resources for the movement, storage, and processing of data and for the control of these functions. The operating system is responsible for managing these resources • 计算机就是一组用于传送、存储和处理数据，并对这些功能进行控制的资源的集合。 而O/S则负责管理这些资源

11. O/S as a Resource Manager(2) • O/S, as a control mechamism, is unusual in two respects:O/S作为控制机制有两个特殊的方面： • The O/S functions in the same way as ordinary computer software; that is, it is a program executed by the processor. O/S以与其它计算机软件相同的方法起作用，即它也是由处理器执行的程序 • The O/S frequently relinquishes control and must depend on the processor to allow it to regain control. O/S经常放弃控制权，并可以依靠处理器重新获得控制权

12. O/S as a Resource Manager(3)

13. Types of Operating System(1) • Interactive 交互式O/S • user/programmer interacts directly with the computer, to request the execution of a job • 用户/程序员直接同计算机进行交互，请求执行作业 • Batch 批处理O/S • some programs are batched and submitted by a computer operator • 多个程序由程序员成批的提交处理

14. Types of Operating System(2) • Single program (Uni-programming): works only one program at a time 单道程序设计：一次只执行一个程序 • Multi-programming (Multi-tasking): work on more than one program at a time 多道程序设计：处理器一次运行多个程序

15. Early Systems(1) • Late 1940s to mid 1950s, No Operating System 40年代末～50年代中, 没有操作系统 • Programmers interacted directly with hardware 程序员直接同硬件交互

16. Early Systems(2) • Two main problems: 早期O/S的两个主要问题 • Scheduling 调度 • used a sign-up sheet to reserve processor time 使用预约单预约机时 • sign-up time < ? > really used time 预约时间 不一定等于真实使用时间 • Setup time 安装时间 • loading compiler and high-level language program 一个作业涉及到把编译程序和高级语言程序装入内存 • saving compiled program 保存已经编译的程序 • linking together the object program 连接目标程序

17. Simple Batch Systems(Monitor) • Resident Monitor program（常驻监督程序） • Users submit jobs to operator 用户向计算机操作员提交作业 • Operator batches jobs and places them on an I device 操作员把作业成批的放到输入设备上 • Monitor controls sequence of events to be processed 监控程序对成批作业的处理顺序进行控制 • When one job is finished, control returns to Monitor which reads next job 一个作业结束后，控制权返回监控程序，读下一个作业 • Monitor handles scheduling 监控程序负责处理调度

18. Memory Layout for Resident Monitor

19. Job Control Language作业控制语言 • This is a special type of programming language used to provide instructions to the monitor.用来向监控程序提供指令的一种特殊类型的程序设计语言 • Usually denoted by $ 通常以$开头 • e.g. • $JOB • $FTN • ... Some Fortran instructions • $LOAD • $RUN • ... Some data • $END

20. Desirable Hardware Features(1) • Memory protection 存储器保护 • To protect the Monitor 为了保护监控程序 • Timer 定时器 • To prevent a job monopolizing the system 为了避免单个作业独占系统 • Privileged instructions 特权指令 • Only executed by Monitor 只能有监控程序执行 • e.g. I/O • Interrupts 中断 • Allows for relinquishing and regaining control 允许监控程序放弃并重新获得控制权

21. Desirable Hardware Features(2) • Processor time = user programs time + monitor time 处理器时间 ＝ 用户程序时间＋监控程序时间

22. Multi-programmed Batch Systems • Problem of simple batch systems 单道批处理系统的缺陷 • Process = CPU burst + I/O burst + CPU burst + I/O burst + … • I/O devices very slow (输入设备慢) • Processor often idle waiting for I/O 处理器经常等待I/O • Low CPU utilization (CPU利用率低) read one record 0.0015 seconds execute 100 instructions 0.0001 seconds write one record 0.0015 seconds total 0.0031 seconds CPU utilization = 3.2%

23. Multi-programmed Batch Systems

24. Multi-programmed Batch Systems • Multiprogramming (multitasking) 多任务 • More than one process in memory 内存中同时处理多个任务 • When one process is waiting for I/O, another can use the CPU 当一个在等待I/O时，另一个可以使用CPU

25. Multi-Programming with Two Programs

26. Multi-Programming with Three Programs

27. Utilization P238table7.2

28. Time Sharing Systems 分时系统 • Allow users to interact directly with the computer 所有用户都直接与计算机交互 • Multi-programming allows a number of users to interact with the computer 多道程序设计允许多个用户同时与计算机交互 • Execute each user program in a short time slot 用户程序按照时间片轮流执行 • n user at one time, each user see 1/n computer speed 若n个用户请求服务，一个用户只能看到计算机有效速度的1/n user1 user2 user3 user1 user2 user3 user1 user2 user3

29. Time Sharing Systems • The key differences between batch multiprogramming and time sharing 批处理和时分的区别