計算機操作系統(tǒng)OperatingSystemOverview

計算機操作系統(tǒng)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（易擴展）1.1.1Overview1.1.2OSasaUser/ComputerInterface(I)Figure2.1LayersandViewsofaComputerSystemComputerHardwareOperatingSystemUtilities(Compiler,Database…)ApplicationsProgramsOperatingSystemDesignerProgrammersEndUserTheoperatingsystemmasks（隱藏）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(釋放控制)andmustdependontheprocessortoallowittoregaincontrol（獲取控制）.OSasResourceManager(IIIFigure2.2)ManagementofCPUManagementofI/ODeviceManagementofMemoryManagementofFilesConcept:Kernel、Nucleus(內(nèi)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串行處理)ExampleInputCalculatePrintProblemsScheduling:TheestimatedtimeisnotaccurateSetuptime:Betweenthesetupprocedure,ifanerroroccurred,thenmustgobacktothebeginningofthesetupsequenceContradictionbetweenhumanandmachine1.2.2SimpleBatchSystemObjectives：SolutioncontradictionbetweenhumanandmachineUsersubmitsthejoboncardsortapetoacomputeroperator(useJCL（jobcontrollanguage))Implement:MonitorFromthePointofViewoftheMonitor(p51)MonitorisresponsiblefortherunningofeveryjobControlsaretransferredbetweenmonitorandotheruserprogramsInterruptprocessingDeviceDriversJobSequencingControlLanguageInterpreterUserProgramAreamonitorMemorylayoutforaresident(駐留)monitorFromthePointofViewoftheProcessorWhenCPUrunscommandofmonitor,themonitorgainsthecontrol.WhenCPUrunscommandofuserprogram,theuserprogramgainsthecontrol.Transferthecontrol:Firstmonitorgainsthecontrol,whenuserprogramloadin,itgainsthecontrol,whentheuserprogramfinishorerror,themonitorregains（重獲）thecontrol.JCL(JobControlLanguage)$JOB//begin$FTN//usingFortrancompileandlink…Fortran//instructions$LOAD//loadinrunablemodules$RUN//running.$END//finishdothejobOtherHardwareFeatureDesirable(p53)Memoryprotection（內(nèi)存保護）:Userspaceandsystemspaceareindependent.E.g.Hardwarecandetectoutsideaccessingerror.Timerinterrupt（時鐘中斷）:Whenthetimerexpires,aninterruptoccurs.Privilegedinstructions（特權(quán)指令）:Canbeexecutedonlybythemonitor.Interrupts:ImprovementefficiencyEasyforrelinquishing（釋放）andregainingcontrol1.2.3MultiprogrammedBatchSystemsReadonerecord 0.0015secondsExecute100instructions 0.0001secondsWriteonerecord 0.0015secondsTOTAL 0.0031secondsFigure2.4SystemUtilizationExampleUniprogramming（單道）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(復雜性)ofMultiprogramming(p57)MemorymanagementSchedulingAlgorithm（算法）:Theprocessor（處理器）mustdecidewhichonetorun.1.2.4Time-SharingSystemsMultipleuserssimultaneously（同時）accessthesystemthroughterminals(終端)Concepts:timeslice（時間片）:qusernum（用戶數(shù)）:nresponsetime（響應時間）:tt=n×qMode:multi-terminals、multi-windowsBatchMultiprogrammingvsTimerSharingBatchMultiprogramming

TimeSharing

Principalobjective

Maximizeprocessoruse

Minimizeresponsetime

Sourceofinstructiontooperatingsystem

Jobcontrollanguagecommandsprovidedwiththejob

Commandsenteredattheterminal

ReducingtheSwappingLoadsbyPartialSwapping（p59）Reducingthespendingforaccessingdisk1.3MajorAchievements（p60）1.3.1Processes(進程)1.3.2Memorymanagement1.3.3Informationprotectionandsecurity1.3.4Schedulingandresourcemanagement1.3.5Systemstructure1.3.1ProcessesAprograminexecutionTheanimatedspirit（活動精靈）ofaprogramTheentity（實體）thatcanbeassigned（分派）toandexecutedonaprocessorThreemajortypesofcomputersystemMultiprogrammingbatchoperationTimesharingReal-timetransaction（處理）systemsErrorsMayHappeninMultiprogrammingImpropersynchronization（同步）:Signalsbeinglostorduplicate（重復）signalsbeingreceived.Failedmutualexclusion(失敗的互斥)Nondeterminate（不確定）programoperation:TheresultisnotuniqueDeadlocks（死鎖）Tosolutetheseproblems,introduceprocessconcept

Processentity(實體)AnexecutableprogramTheassociateddataneededbytheprogramTheexecutioncontext(上下文)oftheprogramProcessImageandProcessSwitch（切換）(p63)1.3.2MemoryManagementProcessisolation（隔離）AutomaticallocationandmanagementSupportofmodular（模塊化）programmingVirtuallymemoryLong-termstorageProtectionandaccesscontrol（訪問控制）Fig2.10TwoViewsofaStorageSystemVirtualProcessorRealProcessorMapper(AddressTranslate)MainMemoryAuxiliaryMemoryVirtualMemoryFiles(a)User’sView(b)OperatingSystemDesigner’sViewVirtualAddressMemoryAddressSwappingRead,WriteCopyLong-termStore1.3.3InformationProtectionandSecurityAccesscontrol:forvariousresourcesinthesystemInformationflowcontrol（信息流控）:toguaranteethedatatosendtodestinationCertification（認證）1.3.4SchedulingandResourceManagement（p66）ThreefactorsmustbeconsiderFairnessDifferentialresponsiveness(區(qū)分服務):e.g.IfaprocessiswaitingfortheuseofanI/Odevice,theoperatingsystemmaywishtoschedulethatprocessforexecutionassoonaspossibleinordertofreeupthedeviceforlaterdemandsfromotherprocesses.Efficiency:Maximizethroughput(吞吐量),minimizeresponsetime,accommodate（容納）asmanyusersaspossibleShort－termqueueAlgorithmusedtouse:roundrobin（輪轉(zhuǎn)）Long－termqueueAlgorithmusedtouse:FIFOInterrupthandler:themethodforgetthecontrolServicecallhandler（系統(tǒng)服務處理）:theentrypointintotheoperatingsystemSomeConcepts（p67）Fig2.11KeyelementsofanOperatingSystemforMultiprogrammingServiceCallHandlerInterruptHandlerLong-termQueueShort-termQueueShort-TermSchedulerI/OqueueOSModules（模塊化）structure:onlysuitableforsmallsystem;forcomplexsystem,difficultfordebugHierarchical（層）structureLevelnprovidesserviceforleveln+1SystemStructure(p68系統(tǒng)結(jié)構(gòu))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（微內(nèi)核結(jié)構(gòu)）1.4.2Multithreading（多線程）1.4.3Symmetricmultiprocess（對稱多處理）1.4.4Distributedoperatingsystems（分布式系統(tǒng)）1.4.5Object-orienteddesign（對象設計）1.4CharacteristicsofModernOS(p71)Assignsonlyafewessential（必要的）functionstothekernel,includingaddressspaces,interprocesscommunication(IPC)（進程間通信）,andbasicscheduling.Simplifiesimpl