操作系统原理及应用

操作系统原理及应用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设计操作系统时采用的模块化内核方法和分层方法在那些方面类似？哪些方面不同？作业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小结（1/2）操作系统概念（管理各种资源、支持程序运行、方便用户使用的程序集）操作系统的基本目标（方便性与高效性）引导程序、中断、中断处理程序、中断向量存储结构：内存（小、易失）、二级存储（大、非易失）、分层结构I/O结构：设备控制器（本地缓冲）、DMA硬件保护：双重模式操作、特权指令、I/O保护、内存保护、CPU保护Part1小结（2/2）操作系统的发展（大型机（无OS、批处理、多道程序设计（并发性、共享性、虚拟性、异步性）、分时）——桌面——并行（紧耦合）——分布式（松耦合，集群）——专用（实时、手持））操作系统的功能：进程（CPU）管理、内存管理、文件管理、磁盘管理、I/O管理、用户接口操作系统的服务：程序执行、I/O操作、文件系统操作、通信、错误检测与处理、资源分配、统计、保护操作系统的接口：用户接口（CLI、GUI）+程序接口（系统调用（参数传递、类型）、SCI、API）操作系统的结构：简单结构、分层结构（虚拟机）、微核结构（进程管理、内存管理、通信功能）、模块化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