操作系統(tǒng)原理及應(yīng)用

操作系統(tǒng)原理及應(yīng)用Chapter2Operating-System

StructuresOperatingSystemFunctionsOperatingSystemServicesOperatingSystemInterfacesOperatingSystemStructureOperatingSystemDesignandImplementationOutlineCommonFunctionsofOSProcessManagementMainMemoryManagementFileManagementSecondary-StorageManagementI/OSystemManagementProcessManagementAprocessisaprograminexecutionSystemProcessesandUserProcessesActivitiesforprocessmanagementProcesscreationanddeletionprocesssuspensionandresumptionProvisionofmechanismsforprocesssynchronizationprocesscommunicationDeadlockhandlingMain-MemoryManagementMemoryisalargearrayofwordsorbytes,eachwithitsownaddress.ItisgenerallytheonlylargestoragedevicethattheCPUisabletoaddressandaccessdirectly.Mainmemoryisavolatilestoragedevice.Activitiesformain-memorymanagementRecordtheusageofMain-memoryAllocateanddeallocatememoryspaceasneededFileManagement(1/2)Therearedifferenttypesofphysicalmediatostoreinformation.Eachofthemhasitsowncharacteristicsandphysicalorganization.AccessspeedData-transferrateAccessmethod(sequentialorrandom)OperatingSystemprovidesauniformlogicalviewofinformationstorage,i.e.,file.Afileisacollectionofrelatedinformation(programsanddata)definedbyitscreator.ActivitiesforfilemanagementFilecreationanddeletionDirectorycreationanddeletionSupportofprimitivesformanipulatingfilesanddirectoriesMappingfilesontosecondarystorageFilebackuponstable(nonvolatile)storagemediaFileManagement(2/2)Secondary-StorageManagementSincemainmemory(primarystorage)isvolatileandtoosmalltoaccommodatealldataandprogramspermanently,thecomputersystemmustprovidesecondarystoragetobackupmainmemory.Mostmoderncomputersystemsusedisksastheprincipleon-linestoragemedium,forbothprogramsanddata.Secondary-StorageManagementActivitiesfordiskmanagementFreespacemanagementStorageallocationDiskschedulingI/OSystemManagementHidingthepeculiaritiesofspecifichardwaredevicesfromtheuserTheI/OsubsystemconsistsofAmemory-managementcomponentincludingbuffer,caching,spoolingAgeneraldevice-driverinterfaceDriversforspecifichardwaredevicesOperatingSystemFunctionsOperatingSystemServicesOperatingSystemInterfacesOperatingSystemStructureOperatingSystemDesignandImplementationOutlineOperatingSystemServices(1/2)ServicesforhelpingUsersProgramexecution–systemcapabilitytoloadaprogramintomemoryandtorunit.I/Ooperations–sinceuserprogramscannotexecuteI/Ooperationsdirectly,theoperatingsystemmustprovidesomemeanstoperformI/O.File-systemmanipulation–programcapabilitytoread,write,create,anddeletefiles.Communications–exchangeofinformationbetweenprocesses(sharedmemoryormessagepassing)Errordetection–ensurecorrectcomputingbydetectingerrorsinhardwaresorinuserprograms.ServicesforensuringsystemoperationsResourceallocation–allocatingresourcestomultipleusersormultiplejobsrunningatthesametime.Accounting–keeptrackofwhichusersusehowmuchandwhatkindsofcomputerresources.Protection–ensuringthatallaccesstosystemresourcesiscontrolledandrecordingalltheconnectionsfordetectionofbreak-ins.OperatingSystemServices(2/2)OperatingSystemFunctionsOperatingSystemServicesOperatingSystemInterfacesOperatingSystemStructureOperatingSystemDesignandImplementationOutlineInterfacestoUsersCommand-LineInterface–textcommandsBatchInterface–filesincludingsomecommandsGraphicalUserInterface–windowsystemOperatingSystemInterfaces(1/4)Command-lineInterpreter(Shell)TheprogramthatreadsandinterpretscontrolstatementsDOSOS:TwowaystoimplementcommandsInternalCommand:Thecommandinterpreteritselfcontainsthecodetoexecutethecommand.(dir,copy)ExternalCommand:Systemprogramesimplementmostcommands.(rm,fdisk,format)OperatingSystemInterfaces(2/4)Graphicaluserinterface(GUI)Desktop：Mouse-basedwindow-and-menusystemIcons,foldersMobilesystemGesturesonthetouchscreenManysystemsnowincludebothCLIandGUIinterfacesOperatingSystemInterfaces(3/4)InterfacestoProgramesSystemcallsTypicallywritteninassembly-languageinstructionsorahigh-levellanguage(CorC++)Mostlyaccessedbyprogramsviaahigh-levelApplicationProgramInterface(API)ratherthandirectsystemcalluseOperatingSystemInterfaces(4/4)ExampleofSystemCallsSystemcallsequencetocopythecontentsofonefiletoanotherfileSystemCallImplementationApplicationProgrammingInterface(API)APIfunctionsinvoketheactualsystemcallsonbehalfoftheapplicationprogrammerJustneedstoobeyAPIandunderstandwhatOSwilldoasaresultcall,mostdetailsofOSinterfacehiddenfromprogrammerbyAPIAPIsareManagedbyrun-timesupportlibrary(setoffunctionsbuiltintolibrariesincludedwithcompiler)SystemCallImplementationSystem-callInterface(SCI)Typically,anumberassociatedwitheachsystemcallSystem-callinterfacemaintainsatableindexedaccordingtothesenumbersThesystemcallinterfaceinvokesintendedsystemcallinOSkernelandreturnsstatusofthesystemcallandanyreturnvaluesDiscussionWhydouseruseAPIsratherthansystemcalls?SystemCallImplementationThreemostcommonAPIsWin32APIforWindowsPOSIXAPIforPOSIX-basedsystems(includingvirtuallyallversionsofUNIX,Linux,andMacOSX)JavaAPIfortheJavavirtualmachine(JVM)RelationshipbetweenAPI,SCI,OSStandardCLibraryExampleCprograminvokingprintf()librarycall,whichcallswrite()systemcallSystemCallParameterPassingOften,moreinformationisrequiredthansimplyidentityofdesiredsystemcallThreegeneralmethodsusedtopassparameterstotheOSSimplest:passtheparametersinregistersParametersstoredinablock,ortable,inmemory,andaddressofblockpassedasaparameterinaregister

Parametersplaced,orpushed,ontothestackbytheprogramandpoppedoffthestackbytheoperatingsystemParameterPassingviaTableTypesofSystemCallsProcesscontrolFilemanagementDevicemanagementInformationmaintenanceCommunicationsTypesofSystemCallsProcesscontrolend,abortload,executecreateandterminateprocessgetandsetprocessattributeswaitfortimewaitevent,signaleventallocateandfreememoryTypesofSystemCallsFilemanagementcreateanddeletefileopenandclosefileread,write,repositiongetandsetfileattributesDevicemanagementrequestandreleasefileread,write,repositiongetandsetdeviceattributeslogicallyattachordetachdevicesTypesofSystemCallsInformationmaintenancegetandsettimeordategetandsetsystemdatagetandsetprocess,fileordeviceattributesCommunicationscreateanddeletecommunicationconnectionsendandreceivemessagetransferstatusinformationattachordetachremotedevicesOperatingSystemFunctionsOperatingSystemServicesOperatingSystemInterfacesOperatingSystemStructureOperatingSystemDesignandImplementationOutlineOperatingSystemStructureSimpleStructureLayeredStructureVirtualMachinesMicrokernelStructureModulesSimpleStructureMS-DOSWrittentoprovidethemostfunctionalityintheleastspaceNotdividedintomodulesAlthoughMS-DOShassomestructure,itsinterfacesandlevelsoffunctionalityarenotwellseparatedMS-DOSLayerStructureOriginalUNIXTwoseparablepartsSystemsprogramsThekernel:Consistsofeverythingbelowthesystem-callinterfaceandabovethephysicalhardware,providesalargenumberoffunctionsforonelevelSimpleStructureUNIXSystemStructureLayeredStructureTheoperatingsystemisdividedintoanumberoflayers(levels),eachbuiltontopoflowerlayers.Thebottomlayer(layer0),isthehardware;thehighest(layerN)istheuserinterface.Withmodularity,layersareselectedsuchthateachusesfunctions(operations)andservicesofonlylower-levellayersLayeredOperatingSystemOS/2LayerStructureMicrokernelStructureMovesasmuchfromthekernelinto“user”spaceTypically,microkernelsprovideminimalprocessmanagement,memorymanagementandcommunicationfacilityCommunicationtakesplacebetweenusermodulesusingmessagepassingMicrokernelStructureBenefitsEasiertoextendaoperatingsystemEasiertoporttheoperatingsystemtonewarchitecturesMorereliable(lesscodeisrunninginkernelmode)MoresecureLacksPerformanceoverheadofuserspacetokernelspacecommunicationModulesMostmodernoperatingsystemsimplementkernelmodulesUsesobject-orientedapproachEachcorecomponentisseparateEachtalkstotheothersoverknowninterfacesEachisloadableasneededwithinthekernelOverall,similartolayersbutwithmoreflexibleSolarisModularApproach設(shè)計操作系統(tǒng)時采用的模塊化內(nèi)核方法和分層方法在那些方面類似？哪些方面不同？作業(yè)1VirtualMachinesAvirtualmachinetakesthelayeredapproachtoitslogicalconclusion.IttreatshardwareandtheoperatingsystemkernelasthoughtheywereallhardwareAvirtualmachineprovidesaninterfaceidenticaltotheunderlyingbarehardwareTheoperatingsystemcreatesthe“illusion”ofmultipleprocesses,eachexecutingonitsownprocessorwithitsown(virtual)memoryVirtualMachinesNon-virtualMachineVirtualMachineVirtualMachinesAdvantagesProvidingcompleteprotectionofsystemresourcesEachvirtualmachineisisolatedfromallothervirtualmachines.Thisisolation,however,permitsnodirectsharingofresources.BeingabletosharethesamehardwareyetrundifferentoperatingsystemsconcurrentlyAperfectvehicleforoperating-systemsresearchanddevelopmentSystemdevelopmentisdoneonthevirtualmachine,sodoesnotdisruptnormalsystemoperation.VMwareArchitectureJavaVirtualMachineCompiledJavaprogramsareplatform-neutralbytecodesexecutedbyaJavaVirtualMachine(JVM).JVMconsistsofclassloaderruntimeinterpreterJust-In-Time(JIT)compilersincreaseperformanceJavaVirtualMachineJavaVirtualMachineOperatingSystemFunctionsOperatingSystemServicesOperatingSystemInterfacesOperatingSystemStructureOperatingSystemDesignandImplementationOutlineWhatanOSActuallyDoes?VirtualizesthephysicalresourcesHandlesissuesrelatedtoConcurrencyStoresfilesPersistentlyOperatingSystemDesignandImplementationDesignandImplementationofOSnot“solvable”,butsomeapproacheshaveprovensuccessfulInternalstructureofdifferentOperatingSystemscanvarywidelyStartbydefininggoalsandspecificationsAffectedbychoiceofhardware,typeofsystemOperatingSystemDesignandImplementationDesigngoalsUsergoals–operatingsystemshouldbeconvenienttouse,easytolearn,reliable,safe,andfastSystemgoals–operatingsystemshouldbeeasytodesign,implement,andmaintain,aswellasflexible,reliable,error-free,andefficientOperatingSystemDesignandImplementationImportantprincipletoseparatePolicy:Whatwillbedone?Mechanism:Howtodoit?Theseparationofpolicyfrommechanismisaveryimportantprinciple,itallowsmaximumflexibilityifpolicydecisionsaretobechangedlaterOperatingSystemDesignandImplementationWrittenmostlyinCorC++Advantage—beingfareasiertoportDisadvantage—reducedspeedandincreasedstoragerequirementsSomesmallsectionsofassemblycodefordevicedriversandforsavingandrestoringthestateofregistersPart1小結(jié)（1/2）操作系統(tǒng)概念（管理各種資源、支持程序運(yùn)行、方便用戶使用的程序集）操作系統(tǒng)的基本目標(biāo)（方便性與高效性）引導(dǎo)程序、中斷、中斷處理程序、中斷向量存儲結(jié)構(gòu)：內(nèi)存（小、易失）、二級存儲（大、非易失）、分層結(jié)構(gòu)I/O結(jié)構(gòu)：設(shè)備控制器（本地緩沖）、DMA硬件保護(hù)：雙重模式操作、特權(quán)指令、I/O保護(hù)、內(nèi)存保護(hù)、CPU保護(hù)Part1小結(jié)（2/2）操作系統(tǒng)的發(fā)展（大型機(jī)（無OS、批處理、多道程序設(shè)計（并發(fā)性、共享性、虛擬性、異步性）、分時）——桌面——并行（緊耦合）——分布式（松耦合，集群）——專用（實(shí)時、手持））操作系統(tǒng)的功能：進(jìn)程（CPU）管理、內(nèi)存管理、文件管理、磁盤管理、I/O管理、用戶接口操作系統(tǒng)的服務(wù)：程序執(zhí)行、I/O操作、文件系統(tǒng)操作、通信、錯誤檢測與處理、資源分配、統(tǒng)計、保護(hù)操作系統(tǒng)的接口：用戶接口（CLI、GUI）+程序接口（系統(tǒng)調(diào)用（參數(shù)傳遞、類型）、SCI、API）操作系統(tǒng)的結(jié)構(gòu)：簡單結(jié)構(gòu)、分層結(jié)構(gòu)（虛擬機(jī)）、微核結(jié)構(gòu)（進(jìn)程管理、內(nèi)存管理、通信功能）、模塊化HistoryEarlyOS：JustLibrariesBatchBeyondLibraries:ProtectionSystemcallinsteadofanormalprocedurecallUsermode/KernelmodeTrap&traphandlerHistoryEraofMultiprogrammingMainfametominicomputerMultiprogrammingMemoryprotectionConcurrencyHistoryTheModernEraMinicomputer–PersonalcomputerDOS:thediskoperatingsystemLackofmemoryprotectionMacOSPainfuljobschedulingModernOSadoptthegoodfeaturesofminicomputerOS.VirtualMachineMonitorsIntroductionMotivationVirtualizingtheCPUVirtualizingtheMemoryTheInformationGapSummaryIntroductionWhatifonewantedtorundifferentoperatingsystemsonthemachineatthesametime?Virtualmachinemonitor(VMM)(alsocalledahypervisor)IBMIntroductionScene:VMMgivestheillusiontoeachrunningOSthatitcontrolsthemachineBehindthescene:VMMisincontrolofthehardware,andmustmultiplexrunningOSesacrossthephysicalresourcesofthemachine.VMMservesasanoperatingsystemforoperatingsystemsIntroductionTheOSmuststillthinkitisinteractingwiththephysicalhardware.TransparencyisamajorgoalofVMMs.IntroductiontoVMwareMarketleaderinvirtualizationtechnologyProfessorMendelRosenblum(Stanford)VirtualMachineMonitorsIntroductionMotivationVirtualizingtheCPUVirtualizingtheMemoryTheInformationGapSummaryMotivationWhyVMMs?Inhistory:IBMmainframesToday:multiplereasonsServerconsolidationApplicationsondifferentplatformsTestinganddebuggingVirtualMachineMonitorsIntroductionMotivationVirtualizingtheCPUVirtualizingtheMemoryTheInformationGapSummaryVirtualizingtheCPUBasictechnique:LimiteddirectexecutionContextswitch–MachineswitchDirectExecutionRestrictedOperationsUsermode/KernelModeInterrupt/trap,handlerSystemcall,API,SCILimitedDirectExecutionRestrictedOperationsDiscussion:WhataboutaTimerInterrupt,insteadofaSoftwareInterrupt?ContextSwitchWillbedetailedinProcessManagement.Save/restorecontext(machinestate)MachineSwitchTheVMMmustsavetheentiremachinestateofoneOS,restorethemachinestateoftheto-be-runVM,andthenjumptothePCoftheto-be-runVMandthuscompletetheswitch.TheOScanbeeitherinusermodeorkernelmode.VirtualizingtheCPUWhatifOStriestoperformaprivilegedoperation？VMMmustsomehowinterceptattemptstoperformprivilegedoperations.Discussion:WHY?Hints:whowilltakecontrolofthemachine?VirtualizingtheCPUWhatifanapplicationtriestomakeasystemcall?Interrupt/trap?Discussion:traditionalsettingwithoutvirtualizationReview:SystemCallVirtualizingtheCPUTransferscontroltoawell-definedtraphandlerwithintheoperatingsystem.ChangesthemodeoftheprocessorfromusermodetokernelmodeVirtualizingtheCPUOnavirtualizedplatform:AfteraninterruptVMMcontrolsthemachine,andthustheVMMwhohasinstalledatraphandlerthatwillfirstgetexecutedinkernelmodeBUT:VMMDOESNOTreallyknowhowtoha