Chapter 1 Operating System Overview OPERATING SYSTEM OVERVIEW Contents Operating System Objectives and Functions The Evolution of Operating System.

Chapter 1 Chapter 1

Operating System OverviewOperating System Overview

OPERATING SYSTEM OVERVIEW

ContentsContents

Operating System Objectives and FunctionsOperating System Objectives and Functions

The Evolution of Operating SystemThe Evolution of Operating System

Major AchievementsMajor Achievements

Characteristics of Modern OSCharacteristics of Modern OS

ExamplesExamples （（ NTNT 、、 UNIXUNIX ））


1.1 Objectives and Functions (p45)1.1 Objectives and Functions (p45)

1.1.1 Overview1.1.1 Overview

1.1.2 The Operating System as a User/Computer Interface1.1.2 The Operating System as a User/Computer Interface

1.1.3 The Operating System as Resource Manager1.1.3 The Operating System as Resource Manager

1.1.4 Ease of Evolution of an Operating System1.1.4 Ease of Evolution of an Operating System


An operating system is a An operating system is a programprogram that manages the that manages the computer, controls the execution of application progcomputer, controls the execution of application programs and acts as an rams and acts as an interfaceinterface(( 接口接口 ) between the us) between the user of a computer and the computer hardware.er of a computer and the computer hardware.

ObjectivesObjectives٭ ConvenienceConvenience （方便）（方便）٭ EfficiencyEfficiency （有效）（有效）٭ Ability to evolveAbility to evolve （易扩展）（易扩展）

1.1.1 Overview1.1.1 Overview


1.1.2 OS as a User/Computer Interface (I)1.1.2 OS as a User/Computer Interface (I)

Figure 2.1 Layers and Views of a Computer System

Computer Hardware

Operating System

Utilities (Compiler, Database…)

Applications Programs

OperatingSystem Designer

Programmers

End User


The operating system The operating system masksmasks （隐藏）（隐藏） the details of the details of the hardware from the programmerthe hardware from the programmer ，， and provideand provides the programmer with a convenient interface for uss the programmer with a convenient interface for using the system.ing the system.

The types of system interfaceThe types of system interface٭ Command interface: system command (internalCommand interface: system command (internal 、、

external)external)٭ Graphics interface: windowsGraphics interface: windows٭ Programmer interface: system call, c-libProgrammer interface: system call, c-lib

OS as a User/Computer Interface (II)OS as a User/Computer Interface (II)


Services of the Operating System (I)Services of the Operating System (I)

Program creationProgram creation٭ Such as: fork (unix)Such as: fork (unix) 、、 CreateProcess (wiCreateProcess (wi

n)n)

Program executionProgram execution٭ Such as: execl, execpSuch as: execl, execp

Access to I/O devicesAccess to I/O devices٭ Such as: read/writeSuch as: read/write

Controlled access to filesControlled access to files٭ Such as: read/writeSuch as: read/write


Services of the Operating System (II)Services of the Operating System (II)

System accessSystem access٭ Provide protection and authorizedProvide protection and authorized

Error detection and responseError detection and response٭ Such as: errorSuch as: error

AccountingAccounting


1.1.3 OS as Resource Manager (I)1.1.3 OS as Resource Manager (I) （（ p47p47 ））

Types of Resource: CPUTypes of Resource: CPU 、、 MemoryMemory 、、 DevicesDevices

CPU: chapter 3.4.5.6.9.10CPU: chapter 3.4.5.6.9.10

Memory: chapter 7.8Memory: chapter 7.8

I/O Devices: chapter 11.12I/O Devices: chapter 11.12


OS as Resource Manager (II)OS as Resource Manager (II)

As a control mechanism is unusual in two respectsAs a control mechanism is unusual in two respects

٭ The OS functions in the same way as ordinary coThe OS functions in the same way as ordinary co

mputer software; that is, it is a program executed mputer software; that is, it is a program executed

by the processor.by the processor.

٭ The OS frequently The OS frequently relinquishes controlrelinquishes control ( ( 释放控释放控制制 )and must depend on the processor to allow it t)and must depend on the processor to allow it t

o o regain controlregain control （获取控制）（获取控制） ..


OS as Resource Manager (III Figure 2.2)OS as Resource Manager (III Figure 2.2)

Management of CPUManagement of CPU

Management of I/O DeviceManagement of I/O Device

Management of MemoryManagement of Memory

Management of FilesManagement of Files

Concept:Concept:

٭ KernelKernel 、、 NucleusNucleus(( 内核内核 ): Always in main memo): Always in main memo

ry, contains the most-frequently-used functionsry, contains the most-frequently-used functions


1.1.4 Ease of Evolution1.1.4 Ease of Evolution （（ p49p49 ））

Reasons for evolutionReasons for evolution٭ hardware upgradeshardware upgrades

▪ Exp: support pagingExp: support paging٭ new servicesnew services٭ fixesfixes

ImplementsImplements٭ software engineering: modulessoftware engineering: modules 、、 layerlayer 、、 obob

ject designject design


1.2 The Evolution of Operating Systems1.2 The Evolution of Operating Systems

1.2.1 Serial Processing1.2.1 Serial Processing

1.2.2 Simple 1.2.2 Simple BatchBatch Systems Systems

1.2.3 1.2.3 MultiprogrammedMultiprogrammed （多道）（多道） Batch SystemsBatch Systems

1.2.4 1.2.4 Time-SharingTime-Sharing Systems Systems


1.2.1 Serial Processing(p501.2.1 Serial Processing(p50 串行处理串行处理 ))

ExampleExample٭ Input Input Calculate Calculate Print Print

ProblemsProblems٭ SchedulingScheduling: The estimated time is not accurate: The estimated time is not accurate٭ Setup timeSetup time: Between the setup procedure, if an : Between the setup procedure, if an

error occurred, then must go back to the error occurred, then must go back to the beginning of the setup sequencebeginning of the setup sequence

٭ Contradiction between human and machineContradiction between human and machine


1.2.2 Simple Batch System1.2.2 Simple Batch System

ObjectivesObjectives ：： Solution contradiction between humaSolution contradiction between huma

n and machinen and machine

٭ User submits the job on cards or tape to a computUser submits the job on cards or tape to a comput

er operator (use JCLer operator (use JCL （（ job control language))job control language))

Implement: MonitorImplement: Monitor


From the Point of View of the Monitor (p51)From the Point of View of the Monitor (p51)

MonitorMonitor is responsible for the ru is responsible for the running of every jobnning of every job

Controls are transferred between Controls are transferred between monitor and other user programsmonitor and other user programs

Interrupt processing

Device Drivers

Job Sequencing

Control Language Interpreter

User Program Area

monitor

Memory layout for a resident(驻留 ) monitor


From the Point of View of the ProcessorFrom the Point of View of the Processor

When CPU runs command of monitor, the monitor When CPU runs command of monitor, the monitor

gains the control.gains the control.

When CPU runs command of user program, the useWhen CPU runs command of user program, the use

r program gains the control.r program gains the control.

Transfer the control:Transfer the control: First monitor gains the control, First monitor gains the control,

when user program load in, it gains the control, wh when user program load in, it gains the control, wh

en the user program finish or error, the monitor regen the user program finish or error, the monitor reg

ainsains （重获）（重获） the control.the control.


JCL (Job Control Language)JCL (Job Control Language)

$JOB //begin$JOB //begin

$FTN //using Fortran compile and link$FTN //using Fortran compile and link

……Fortran //instructionsFortran //instructions

$LOAD //load in runable modules$LOAD //load in runable modules

$RUN //running.$RUN //running.

$END //finish do the job$END //finish do the job


Other Hardware Feature Desirable(p53)Other Hardware Feature Desirable(p53)

Memory protectionMemory protection （内存保护）（内存保护） :: User space and system s User space and system space are independent.pace are independent.

٭ E.g. Hardware can detect outside accessing error.E.g. Hardware can detect outside accessing error.

Timer interruptTimer interrupt （时钟中断）（时钟中断） :: When the timer expires, an When the timer expires, an interrupt occurs.interrupt occurs.

Privileged instructionsPrivileged instructions （特权指令）（特权指令） :: Can be executed only Can be executed only by the monitor.by the monitor.

Interrupts:Interrupts:

٭ Improvement efficiencyImprovement efficiency

٭ Easy for relinquishingEasy for relinquishing （释放）（释放） and regaining controland regaining control


1.2.3 Multiprogrammed Batch Systems1.2.3 Multiprogrammed Batch Systems

Read one record 0.0015 seconds

Execute 100 instructions 0.0001 seconds

Write one record 0.0015 seconds

TOTAL 0.0031 seconds

Percent CPU Utilization = 0.0001/0.0031=3.2%

Figure 2.4 System Utilization Example

UniprogrammingUniprogramming （单道）（单道） has low efficiencyhas low efficiency （效率）（效率） : : ٭ CPU---I/O contradictionCPU---I/O contradiction


Multiprogramming/MultitaskingMultiprogramming/Multitasking

There are many user programs in the There are many user programs in the memory.memory.

Hardware need for Multiprogramming.Hardware need for Multiprogramming.٭ InterruptionInterruption

For example: p55 Fig2.5For example: p55 Fig2.5


Example of MultiprogrammingExample of Multiprogramming

256k available memory Notes: not consider the resource competitionNotes: not consider the resource competition

JOB1 JOB2 JOB3

Type of JOB Heavy Computer Heavy I/O Heavy I/O

Duration 5min 15min 10min

Memory required 50k 100k 80k

Need disk No No Yes

Need terminal No Yes No

Need printer No No Yes

Table 2.1 Sample Program Execution Attributes


AnalysisAnalysis


AnalysisAnalysis

Single

٭ Processor use ＝ 5/(5+15+10)=17%

٭ Memory use=[(50*5+100*15+80*10)/256/30] =33%

٭ Disk use=10/30=33%

٭ Printer use ＝ 10/30=33%

٭ Total time ＝ 5+15+10 ＝ 30

٭ Throughput ＝ 6 job/hour

٭ Mean response time ＝（ 5+20+30 ） /3=18


AnalysisAnalysis

MultiprogrammingMultiprogramming

٭ Processor use ＝ 5/15=33%

٭ Memory use=[(50+100+80)*5+(100+80)*5+100*5]/256/15 =65%

٭ Disk use=10/15=67%

٭ Printer use ＝ 10/15=67%

٭ Total time ＝ 15

٭ Throughout ＝ 12job/hour

٭ Mean response time ＝（ 5+10+15 ） /3=10


Sophisticated(Sophisticated( 复杂性复杂性 ) of Multiprogramming (p57)) of Multiprogramming (p57)

Memory managementMemory management

Scheduling Scheduling

٭ AlgorithmAlgorithm （算法）（算法） : The processor: The processor （处理器）（处理器） must decide which one to run.must decide which one to run.


1.2.4 T1.2.4 Time-Sharing Systemsime-Sharing Systems

Multiple users simultaneouslyMultiple users simultaneously （同时）（同时） access the system thaccess the system th

rough terminals(rough terminals( 终端终端 ))

Concepts: Concepts:

٭ time slicetime slice （时间片）（时间片） : q: q

٭ user numuser num （用户数）（用户数） : n: n

٭ response timeresponse time （响应时间）（响应时间） : t: t

٭ t=n×qt=n×q

Mode: multi-terminalsMode: multi-terminals 、、 multi-windowsmulti-windows


Batch Multiprogramming vs Timer SharingBatch Multiprogramming vs Timer Sharing

Batch Multiprogramming

Time Sharing

Principal objecPrincipal objectivetive

Maximize processor Maximize processor useuse

Minimize response Minimize response timetime

Source of instrSource of instruction to operauction to operating systemting system

Job control language Job control language commands provided commands provided with the jobwith the job

Commands entered Commands entered at the terminalat the terminal


Reducing the Swapping Loads by Partial SwappingReducing the Swapping Loads by Partial Swapping （（ p59p59 ））

Reducing the spending for accessing disk


1.3 Major Achievements1.3 Major Achievements （（ p60p60 ））

1.3.1 Processes(1.3.1 Processes( 进程进程 ))

1.3.2 Memory management1.3.2 Memory management

1.3.3 Information protection and security1.3.3 Information protection and security

1.3.4 Scheduling and resource management1.3.4 Scheduling and resource management

1.3.5 System structure1.3.5 System structure


1.3.1 Processes1.3.1 Processes

A program in executionA program in execution

The animated spiritThe animated spirit （活动精灵）（活动精灵） of a programof a program

The entityThe entity （实体）（实体） that can be assignedthat can be assigned （分派）（分派） to and eto and e

xecuted on a processorxecuted on a processor

Three major types of computer systemThree major types of computer system

٭ Multiprogramming batch operationMultiprogramming batch operation

٭ Time sharingTime sharing

٭ Real-time transactionReal-time transaction （处理）（处理） systemssystems


Errors May Happen in MultiprogrammingErrors May Happen in Multiprogramming

Improper synchronizationImproper synchronization （同步）（同步） : Signals being : Signals being

lost or duplicatelost or duplicate （重复）（重复） signals being received.signals being received.

Failed mutual exclusionFailed mutual exclusion(( 失败的互斥失败的互斥 ))

NondeterminateNondeterminate （不确定）（不确定） program operationprogram operation: T: T

he result is not uniquehe result is not unique

DeadlocksDeadlocks （死锁）（死锁）To solute these problems, introduce process conceptTo solute these problems, introduce process concept


Process entity(Process entity( 实体实体 ))

An executable programAn executable program

The associated data needed by the programThe associated data needed by the program

The execution context(The execution context( 上下文上下文 ) of the program) of the program


Process Image and Process SwitchProcess Image and Process Switch （切换）（切换） (p63)(p63)


1.3.2 Memory Management1.3.2 Memory Management

Process isolationProcess isolation （隔离）（隔离）Automatic allocation and managementAutomatic allocation and management

Support of modularSupport of modular （模块化）（模块化） programmingprogramming

Virtually memoryVirtually memory

Long-term storageLong-term storage

Protection and access controlProtection and access control （访问控制）（访问控制）


Fig 2.10 Two Views of a Storage System

Virtual Processor

Real Processor

Mapper (AddressTranslate)

Main Memory

AuxiliaryMemory

VirtualMemory

Files

(a) User’s View

(b) Operating System Designer’s View

VirtualAddress

MemoryAddress Swapping

Read, Write Copy

Long-term Store


1.3.3 Information Protection and Security1.3.3 Information Protection and Security

Access controlAccess control: for various resources in the system: for various resources in the system

Information flow controlInformation flow control （信息流控）（信息流控） : to guarant: to guarant

ee the data to send to destinationee the data to send to destination

CertificationCertification （认证）（认证）


1.3.4 Scheduling and Resource Management1.3.4 Scheduling and Resource Management （（ p66p66 ））

Three factors must be considerThree factors must be consider

٭ FairnessFairness

٭ Differential responsivenessDifferential responsiveness(( 区分服务区分服务 ): ): e.g.e.g. If a process i If a process is waiting for the use of an I/O device, the operating systes waiting for the use of an I/O device, the operating system may wish to schedule that process for execution as soon m may wish to schedule that process for execution as soon as possible in order to free up the device for later demandas possible in order to free up the device for later demands from other processes.s from other processes.

٭ EfficiencyEfficiency: Maximize throughput(: Maximize throughput( 吞吐量吞吐量 ), minimize res), minimize response time, accommodateponse time, accommodate （容纳）（容纳） as many users as posas many users as possiblesible


ShortShort －－ term queueterm queue

٭ Algorithm used to use: round robinAlgorithm used to use: round robin （轮转）（轮转） LongLong －－ term queueterm queue

٭ Algorithm used to use: FIFOAlgorithm used to use: FIFO

Interrupt handler: the method for get the controlInterrupt handler: the method for get the control

Service call handlerService call handler （系统服务处理）（系统服务处理） : the entry point into : the entry point into

the operating systemthe operating system

Some ConceptsSome Concepts （（ p67p67 ））


Fig 2.11 Key elements of an Operating System for Multiprogramming

Service CallHandler

InterruptHandler

Long-term Queue

Short-term Queue

Short-Term Scheduler

I/O queue

OS


ModulesModules （模块化）（模块化） structure: only suitable for smstructure: only suitable for sm

all system; for complex system, difficult for debugall system; for complex system, difficult for debug

HierarchicalHierarchical （层）（层） structurestructure

٭ Level n provides service for level n+1Level n provides service for level n+1

System Structure(p68System Structure(p68 系统结构系统结构 ))


Hierarchy (Table 2.4)Hierarchy (Table 2.4)

LevelLevel NameName ObjectsObjects Example OperationsExample Operations

1313 ShellShell User programmingUser programming Statements in shell languageStatements in shell languageenvironmentenvironment

1212 User processesUser processes User processesUser processes Quit, kill, suspend, resumeQuit, kill, suspend, resume

1111 DirectoriesDirectories DirectoriesDirectories Create, destroy, attach, detach,Create, destroy, attach, detach,search, listsearch, list

1010 DevicesDevices External devicesExternal devices Open, close,Open, close,as printer, displaysas printer, displays read, writeread, writeand keyboardsand keyboards

99 File systemFile system FilesFiles Create, destroy, open, closeCreate, destroy, open, closeread, writeread, write

88 CommunicationsCommunications PipesPipes Create, destroy, open, close,Create, destroy, open, close,read, writeread, write


HierarchyHierarchy

LevelLevel NameName ObjectsObjects Example Operations Example Operations

77 Virtual MemoryVirtual Memory Segments, pagesSegments, pages Read, write, fetch Read, write, fetch

66 Local secondaryLocal secondary Blocks of data, deviceBlocks of data, device Read, write, allocate, freeRead, write, allocate, freestorestore channelschannels

55 Primitive processes Primitive process,Primitive processes Primitive process, Suspend, resume, wait, Suspend, resume, wait, semaphores, readysemaphores, ready signalsignal listlist


Hierarchy (Hardware)Hierarchy (Hardware)

LevelLevel NameName ObjectsObjects Example Operations Example Operations

44 InterruptsInterrupts Interrupt-handlingInterrupt-handling Invoke, mask, unmask, Invoke, mask, unmask, retryretry

programsprograms

33 ProceduresProcedures Procedures, call stack, Procedures, call stack, Mark stack, call, Mark stack, call, returnreturn

displaydisplay

22 Instruction SetInstruction Set Evaluation stack, micro-Evaluation stack, micro- Load, store, add, Load, store, add, subtractsubtract

program interpreter,program interpreter, branch branchscalar and array datascalar and array data

11 Electronic circuitsElectronic circuits Registers, gates, buses,Registers, gates, buses, Clear, transfer, Clear, transfer, activate,activate,

etc.etc. complement complement


1.4.1 Microkernel architecture1.4.1 Microkernel architecture （微内核结构）（微内核结构）

1.4.2 Multithreading1.4.2 Multithreading （多线程）（多线程）

1.4.3 Symmetric multiprocess1.4.3 Symmetric multiprocess （对称多处理）（对称多处理）

1.4.4 Distributed operating systems1.4.4 Distributed operating systems （分布式系统）（分布式系统）

1.4.5 Object-oriented design1.4.5 Object-oriented design （对象设计）（对象设计）

1.4 Characteristics of Modern OS (p71)1.4 Characteristics of Modern OS (p71)


Assigns only a few essentialAssigns only a few essential （必要的）（必要的） functions to functions to

the kernel, including address spaces, interprocess cthe kernel, including address spaces, interprocess c

ommunication(IPC)ommunication(IPC) （进程间通信）（进程间通信） , and basic sch, and basic sch

eduling.eduling.

Simplifies implementation, provides flexibilitySimplifies implementation, provides flexibility （伸（伸缩性）缩性） and well suited to a distributed environment.and well suited to a distributed environment.

1.4.1 Microkernel 1.4.1 Microkernel


1.4.2 Multithreading1.4.2 Multithreading

ThreadThread ：： a dispatchablea dispatchable （分派）（分派） unit of workunit of work

ProcessProcess ：： a collection of one or more threads and aa collection of one or more threads and a

ssociatedssociated （相关）（相关） system resourcessystem resources

Introduce thread for improve the concurrence degreIntroduce thread for improve the concurrence degre

ee （并发度）（并发度）E.g.E.g. ：： a database server accept many connection rea database server accept many connection re

quest and use multithread for processquest and use multithread for process


1.4.3 Symmetric Multiprocessing (SMP p73)1.4.3 Symmetric Multiprocessing (SMP p73)

A computer hardware architecture and also to the operating A computer hardware architecture and also to the operating system behavior that reflects that architecture.system behavior that reflects that architecture.

٭ Multiple processorsMultiple processors

٭ These processors share the same main memory and I/O faThese processors share the same main memory and I/O fa

cilities, interconnected by a bus or other internal connecticilities, interconnected by a bus or other internal connecti

on scheme.on scheme.

٭ All processors can perform the same functionsAll processors can perform the same functions （（ hence thence t

he term symmetriche term symmetric ））


SMP vs Single ProcessorSMP vs Single Processor

Performance: parallel and concurrencePerformance: parallel and concurrence （并行与并（并行与并发）发）

Reliability/AvailabilityReliability/Availability （可靠性（可靠性 // 可用性）可用性）Incremental growthIncremental growth （可伸展性）（可伸展性） : enhance the per: enhance the per

formance of a system by adding an additional proceformance of a system by adding an additional proce

ssorssor


SMP vs Single Processor (Figure 2.12)SMP vs Single Processor (Figure 2.12)


1.4.4 Distributed Operating System1.4.4 Distributed Operating System

Data distributedData distributed

Task distributedTask distributed

TransparentTransparent （透明）（透明） : a multi-processor with a : a multi-processor with a

single processor charactersingle processor character

High throughout and reliabilityHigh throughout and reliability


1.4.5 Object Design1.4.5 Object Design

Encapsulation and inheritEncapsulation and inherit （封装和继承）（封装和继承）

Good scalabilityGood scalability （尺度特征）（尺度特征）

Chapter 1 Operating System Overview OPERATING SYSTEM OVERVIEW Contents Operating System Objectives and Functions The Evolution of Operating System.

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