计算机操作系统OperatingSystemOverview

计算机操作系统OperatingSystemOverviewContentsOperatingSystemObjectivesandFunctionsTheEvolutionofOperatingSystemMajorAchievementsCharacteristicsofModernOSExamples（NT、UNIX）1.1ObjectivesandFunctions(p45)1.1.1Overview1.1.2TheOperatingSystemasaUser/ComputerInterface1.1.3TheOperatingSystemasResourceManager1.1.4EaseofEvolutionofanOperatingSystemAnoperatingsystemisaprogramthatmanagesthecomputer,controlstheexecutionofapplicationprogramsandactsasaninterface(接口)betweentheuserofacomputerandthecomputerhardware.ObjectivesConvenience（方便）Efficiency（有效）Abilitytoevolve（易扩展）1.1.1Overview1.1.2OSasaUser/ComputerInterface(I)Figure2.1LayersandViewsofaComputerSystemComputerHardwareOperatingSystemUtilities(Compiler,Database…)ApplicationsProgramsOperatingSystemDesignerProgrammersEndUserTheoperatingsystemmasks（隐藏）thedetailsofthehardwarefromtheprogrammer，andprovidestheprogrammerwithaconvenientinterfaceforusingthesystem.ThetypesofsysteminterfaceCommandinterface:systemcommand(internal、external)Graphicsinterface:windowsProgrammerinterface:systemcall,c-libOSasaUser/ComputerInterface(II)ServicesoftheOperatingSystem(I)ProgramcreationSuchas:fork(unix)、CreateProcess(win)ProgramexecutionSuchas:execl,execpAccesstoI/OdevicesSuchas:read/writeControlledaccesstofilesSuchas:read/writeServicesoftheOperatingSystem(II)SystemaccessProvideprotectionandauthorizedErrordetectionandresponseSuchas:errorAccounting1.1.3OSasResourceManager(I)（p47）TypesofResource:CPU、Memory、DevicesOSasResourceManager(II)AsacontrolmechanismisunusualintworespectsTheOSfunctionsinthesamewayasordinarycomputersoftware;thatis,itisaprogramexecutedbytheprocessor.TheOSfrequentlyrelinquishescontrol(释放控制)andmustdependontheprocessortoallowittoregaincontrol（获取控制）.OSasResourceManager(IIIFigure2.2)ManagementofCPUManagementofI/ODeviceManagementofMemoryManagementofFilesConcept:Kernel、Nucleus(内核):Alwaysinmainmemory,containsthemost-frequently-usedfunctions1.1.4EaseofEvolution（p49）ReasonsforevolutionhardwareupgradesExp:supportpagingnewservicesfixesImplementssoftwareengineering:modules、layer、objectdesign1.2TheEvolutionofOperatingSystems1.2.1SerialProcessing1.2.2SimpleBatchSystems1.2.3Multiprogrammed（多道）BatchSystems1.2.4Time-SharingSystems1.2.1SerialProcessing(p50串行处理)ExampleInputCalculatePrintProblemsScheduling:TheestimatedtimeisnotaccurateSetuptime:Betweenthesetupprocedure,ifanerroroccurred,thenmustgobacktothebeginningofthesetupsequenceContradictionbetweenhumanandmachine1.2.2SimpleBatchSystemObjectives：SolutioncontradictionbetweenhumanandmachineUsersubmitsthejoboncardsortapetoacomputeroperator(useJCL（jobcontrollanguage))Implement:MonitorFromthePointofViewoftheMonitor(p51)MonitorisresponsiblefortherunningofeveryjobControlsaretransferredbetweenmonitorandotheruserprogramsInterruptprocessingDeviceDriversJobSequencingControlLanguageInterpreterUserProgramAreamonitorMemorylayoutforaresident(驻留)monitorFromthePointofViewoftheProcessorWhenCPUrunscommandofmonitor,themonitorgainsthecontrol.WhenCPUrunscommandofuserprogram,theuserprogramgainsthecontrol.Transferthecontrol:Firstmonitorgainsthecontrol,whenuserprogramloadin,itgainsthecontrol,whentheuserprogramfinishorerror,themonitorregains（重获）thecontrol.JCL(JobControlLanguage)$JOB//begin$FTN//usingFortrancompileandlink…Fortran//instructions$LOAD//loadinrunablemodules$RUN//running.$END//finishdothejobOtherHardwareFeatureDesirable(p53)Memoryprotection（内存保护）:Userspaceandsystemspaceareindependent.E.g.Hardwarecandetectoutsideaccessingerror.Timerinterrupt（时钟中断）:Whenthetimerexpires,aninterruptoccurs.Privilegedinstructions（特权指令）:Canbeexecutedonlybythemonitor.Interrupts:ImprovementefficiencyEasyforrelinquishing（释放）andregainingcontrol1.2.3MultiprogrammedBatchSystemsReadonerecord 0.0015secondsExecute100instructions 0.0001secondsWriteonerecord 0.0015secondsTOTAL 0.0031secondsFigure2.4SystemUtilizationExampleUniprogramming（单道）haslowefficiency（效率）:CPUI/OcontradictionMultiprogramming/MultitaskingTherearemanyuserprogramsinthememory.HardwareneedforMultiprogramming.InterruptionExampleofMultiprogramming256kavailablememoryNotes:notconsidertheresourcecompetitionJOB1JOB2JOB3TypeofJOBHeavyComputerHeavyI/OHeavyI/ODuration5min15min10minMemoryrequired50k100k80kNeeddiskNoNoYesNeedterminalNoYesNoNeedprinterNoNoYesTable2.1SampleProgramExecutionAttributesAnalysisAnalysisSingleProcessoruse＝5/(5+15+10)=17%Memoryuse=[(50*5+100*15+80*10)/256/30]=33%Diskuse=10/30=33%Printeruse＝10/30=33%Totaltime＝5+15+10＝30Throughput＝6job/hourMeanresponsetime＝（5+20+30）/3=18AnalysisMultiprogrammingProcessoruse＝5/15=33%Memoryuse=[(50+100+80)*5+(100+80)*5+100*5]/256/15=65%Diskuse=10/15=67%Printeruse＝10/15=67%Totaltime＝15Throughout＝12job/hourMeanresponsetime＝（5+10+15）/3=10Sophisticated(复杂性)ofMultiprogramming(p57)MemorymanagementSchedulingAlgorithm（算法）:Theprocessor（处理器）mustdecidewhichonetorun.1.2.4Time-SharingSystemsMultipleuserssimultaneously（同时）accessthesystemthroughterminals(终端)Concepts:timeslice（时间片）:qusernum（用户数）:nresponsetime（响应时间）:tt=n×qMode:multi-terminals、multi-windowsBatchMultiprogrammingvsTimerSharingBatchMultiprogramming

TimeSharing

Principalobjective

Maximizeprocessoruse

Minimizeresponsetime

Sourceofinstructiontooperatingsystem

Jobcontrollanguagecommandsprovidedwiththejob

Commandsenteredattheterminal

ReducingtheSwappingLoadsbyPartialSwapping（p59）Reducingthespendingforaccessingdisk1.3MajorAchievements（p60）1.3.1Processes(进程)1.3.2Memorymanagement1.3.3Informationprotectionandsecurity1.3.4Schedulingandresourcemanagement1.3.5Systemstructure1.3.1ProcessesAprograminexecutionTheanimatedspirit（活动精灵）ofaprogramTheentity（实体）thatcanbeassigned（分派）toandexecutedonaprocessorThreemajortypesofcomputersystemMultiprogrammingbatchoperationTimesharingReal-timetransaction（处理）systemsErrorsMayHappeninMultiprogrammingImpropersynchronization（同步）:Signalsbeinglostorduplicate（重复）signalsbeingreceived.Failedmutualexclusion(失败的互斥)Nondeterminate（不确定）programoperation:TheresultisnotuniqueDeadlocks（死锁）Tosolutetheseproblems,introduceprocessconcept

Processentity(实体)AnexecutableprogramTheassociateddataneededbytheprogramTheexecutioncontext(上下文)oftheprogramProcessImageandProcessSwitch（切换）(p63)1.3.2MemoryManagementProcessisolation（隔离）AutomaticallocationandmanagementSupportofmodular（模块化）programmingVirtuallymemoryLong-termstorageProtectionandaccesscontrol（访问控制）Fig2.10TwoViewsofaStorageSystemVirtualProcessorRealProcessorMapper(AddressTranslate)MainMemoryAuxiliaryMemoryVirtualMemoryFiles(a)User’sView(b)OperatingSystemDesigner’sViewVirtualAddressMemoryAddressSwappingRead,WriteCopyLong-termStore1.3.3InformationProtectionandSecurityAccesscontrol:forvariousresourcesinthesystemInformationflowcontrol（信息流控）:toguaranteethedatatosendtodestinationCertification（认证）1.3.4SchedulingandResourceManagement（p66）ThreefactorsmustbeconsiderFairnessDifferentialresponsiveness(区分服务):e.g.IfaprocessiswaitingfortheuseofanI/Odevice,theoperatingsystemmaywishtoschedulethatprocessforexecutionassoonaspossibleinordertofreeupthedeviceforlaterdemandsfromotherprocesses.Efficiency:Maximizethroughput(吞吐量),minimizeresponsetime,accommodate（容纳）asmanyusersaspossibleShort－termqueueAlgorithmusedtouse:roundrobin（轮转）Long－termqueueAlgorithmusedtouse:FIFOInterrupthandler:themethodforgetthecontrolServicecallhandler（系统服务处理）:theentrypointintotheoperatingsystemSomeConcepts（p67）Fig2.11KeyelementsofanOperatingSystemforMultiprogrammingServiceCallHandlerInterruptHandlerLong-termQueueShort-termQueueShort-TermSchedulerI/OqueueOSModules（模块化）structure:onlysuitableforsmallsystem;forcomplexsystem,difficultfordebugHierarchical（层）structureLevelnprovidesserviceforleveln+1SystemStructure(p68系统结构)Hierarchy(Table2.4)Level Name Objects ExampleOperations13 Shell Userprogramming Statementsinshelllanguage environment12 Userprocesses Userprocesses Quit,kill,suspend,resume11 Directories Directories Create,destroy,attach,detach, search,list10 Devices Externaldevices Open,close, asprinter,displays read,write

andkeyboards9 Filesystem Files Create,destroy,open,close

read,write8 Communications Pipes Create,destroy,open,close,

read,writeHierarchyLevel Name Objects ExampleOperations7 VirtualMemory Segments,pages Read,write,fetch6 Localsecondary Blocksofdata,device Read,write,allocate,free

store channels5 PrimitiveprocessesPrimitiveprocess, Suspend,resume,wait, semaphores,ready

signal list

Hierarchy(Hardware)Level Name Objects ExampleOperations4 Interrupts Interrupt-handling Invoke,mask,unmask,retry programs

Procedures Procedures,callstack, Markstack,call,return display2 InstructionSet Evaluationstack,micro- Load,store,add,subtract programinterpreter, branch scalarandarraydata1 Electroniccircuits Registers,gates,buses, Clear,transfer,activate, etc. complement1.4.1Microkernelarchitecture（微内核结构）1.4.2Multithreading（多线程）1.4.3Symmetricmultiprocess（对称多处理）1.4.4Distributedoperatingsystems（分布式系统）1.4.5Object-orienteddesign（对象设计）1.4CharacteristicsofModernOS(p71)Assignsonlyafewessential（必要的）functionstothekernel,includingaddressspaces,interprocesscommunication(IPC)（进程间通信）,andbasicscheduling.Simplifiesimpl