操作系统原理课件ch03

Chapter3:Operating-SystemStructuresSystemComponentsOperatingSystemServicesSystemCallsSystemProgramsSystemStructureVirtualMachinesSystemDesignandImplementationSystemGenerationOperatingSystemChapter3:Operating-SystemSCommonSystemComponentsProcessManagementMainMemoryManagementFileManagementI/OSystemManagementSecondaryManagementNetworkingProtectionSystemCommand-InterpreterSystemOperatingSystemCommonSystemComponentsProcesProcessManagementAprocessisaprograminexecution.Aprocessneedscertainresources,includingCPUtime,memory,files,andI/Odevices,toaccomplishitstask.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithprocessmanagement.Pcesssuspensionandresumption.Provisionofmechanismsfor:processsynchronizationprocesscommunicationOperatingSystemProcessManagementAprocessisMain-MemoryManagementMemoryisalargearrayofwordsorbytes,eachwithitsownaddress.ItisarepositoryofquicklyaccessibledatasharedbytheCPUandI/Odevices.Mainmemoryisavolatilestoragedevice.Itlosesitscontentsinthecaseofsystemfailure.OperatingSystemMain-MemoryManagementMemoryiTheoperatingsystemisresponsibleforthefollowingactivitiesinconnectionswithmemorymanagement:Keeptrackofwhichpartsofmemoryarecurrentlybeingusedandbywhom.Decidewhichprocessestoloadwhenmemoryspacebecomesavailable.Allocateanddeallocatememoryspaceasneeded.OperatingSystemTheoperatingsystemisresponFileManagementAfileisacollectionofrelatedinformationdefinedbyitscreator.Commonly,filesrepresentprograms(bothsourceandobjectforms)anddata.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionswithfilemanagement:Filecreationanddeletion.Directorycreationanddeletion.Supportofprimitivesformanipulatingfilesanddirectories.Mappingfilesontosecondarystorage.Filebackuponstable(nonvolatile)storagemedia.OperatingSystemFileManagementAfileisacolI/OSystemManagementTheI/Osystemconsistsof:Abuffer-cachingsystemAgeneraldevice-driverinterfaceDriversforspecifichardwaredevicesOperatingSystemI/OSystemManagementTheI/OsSecondary-StorageManagementSincemainmemory(primarystorage)isvolatileandtoosmalltoaccommodatealldataandprogramspermanently,thecomputersystemmustprovidesecondarystoragetobackupmainmemory.OperatingSystemSecondary-StorageManagementSiMostmoderncomputersystemsusedisksastheprincipleon-linestoragemedium,forbothprogramsanddata.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithdiskmanagement:FreespacemanagementStorageallocationDiskschedulingOperatingSystemMostmoderncomputersystemsuCommand-InterpreterSystemManycommandsaregiventotheoperatingsystembycontrolstatementswhichdealwith:processcreationandmanagementI/Ohandlingsecondary-storagemanagementmain-memorymanagementfile-systemaccessprotectionnetworkingOperatingSystemCommand-InterpreterSystemManyCommand-InterpreterSystem(Cont.)Theprogramthatreadsandinterpretscontrolstatementsiscalledvariously:command-lineinterpretershell(inUNIX)

Itsfunctionistogetandexecutethenextcommandstatement.OperatingSystemCommand-InterpreterSystem(CoOperatingSystemServicesProgramexecution–systemcapabilitytoloadaprogramintomemoryandtorunit.I/Ooperations–sinceuserprogramscannotexecuteI/Ooperationsdirectly,theoperatingsystemmustprovidesomemeanstoperformI/O.File-systemmanipulation–programcapabilitytoread,write,create,anddeletefiles.OperatingSystemOperatingSystemServicesProgrCommunications–exchangeofinformationbetweenprocessesexecutingeitheronthesamecomputerorondifferentsystemstiedtogetherbyanetwork.Implementedviasharedmemoryormessagepassing.Errordetection–ensurecorrectcomputingbydetectingerrorsintheCPUandmemoryhardware,inI/Odevices,orinuserprograms.OperatingSystemCommunications–exchangeofiAdditionalOperatingSystemFunctionsAdditionalfunctionsexistnotforhelpingtheuser,butratherforensuringefficientsystemoperations.Resourceallocation–allocatingresourcestomultipleusersormultiplejobsrunningatthesametime.Accounting–keeptrackofandrecordwhichusersusehowmuchandwhatkindsofcomputerresourcesforaccountbillingorforaccumulatingusagestatistics.Protection–ensuringthatallaccesstosystemresourcesiscontrolled.OperatingSystemAdditionalOperatingSystemFuSystemCallsSystemcallsprovidetheinterfacebetweenarunningprogramandtheoperatingsystem.Generallyavailableasassembly-languageinstructions.Languagesdefinedtoreplaceassemblylanguageforsystemsprogrammingallowsystemcallstobemadedirectly(e.g.,C,C++)OperatingSystemSystemCallsSystemcallsproviThreegeneralmethodsareusedtopassparametersbetweenarunningprogramandtheoperatingsystem.Passparametersinregisters.Storetheparametersinatableinmemory,andthetableaddressispassedasaparameterinaregister.Push(store)theparametersontothestackbytheprogram,andpopoffthestackbyoperatingsystem.OperatingSystemThreegeneralmethodsareusedPassingofParametersAsATableOperatingSystemPassingofParametersAsATabTypesofSystemCallsProcesscontrolFilemanagementDevicemanagementInformationmaintenanceCommunicationsOperatingSystemTypesofSystemCallsProcesscMS-DOSExecutionAtSystemStart-upRunningaProgramOperatingSystemMS-DOSExecutionAtSystemStarUNIXRunningMultipleProgramsOperatingSystemUNIXRunningMultipleProgramsCommunicationModelsMsgPassingSharedMemoryCommunicationmaytakeplaceusingeithermessagepassingorsharedmemory.OperatingSystemCommunicationModelsMsgPassinSystemProgramsSystemprogramsprovideaconvenientenvironmentforprogramdevelopmentandexecution.Thecanbedividedinto:FilemanipulationStatusinformationFilemodificationProgramminglanguagesupportProgramloadingandexecutionCommunicationsApplicationprogramsMostusers’viewoftheoperationsystemisdefinedbysystemprograms,nottheactualsystemcalls.

OperatingSystemSystemProgramsSystemprogramsMS-DOSSystemStructureMS-DOS–writtentoprovidethemostfunctionalityintheleastspacenotdividedintomodulesAlthoughMS-DOShassomestructure,itsinterfacesandlevelsoffunctionalityarenotwellseparatedOperatingSystemMS-DOSSystemStructureMS-DOSMS-DOSLayerStructureOperatingSystemMS-DOSLayerStructureOperatinUNIXSystemStructure

UNIX–limitedbyhardwarefunctionality,theoriginalUNIXoperatingsystemhadlimitedstructuring.TheUNIXOSconsistsoftwoseparableparts.SystemsprogramsThekernelConsistsofeverythingbelowthesystem-callinterfaceandabovethephysicalhardwareProvidesthefilesystem,CPUscheduling,memorymanagement,andotheroperating-systemfunctions;alargenumberoffunctionsforonelevel.OperatingSystemUNIXSystemStructureUNIX–lUNIXSystemStructureOperatingSystemUNIXSystemStructureOperatingLayeredApproachTheoperatingsystemisdividedintoanumberoflayers(levels),eachbuiltontopoflowerlayers.Thebottomlayer(layer0),isthehardware;thehighest(layerN)istheuserinterface.Withmodularity,layersareselectedsuchthateachusesfunctions(operations)andservicesofonlylower-levellayers.OperatingSystemLayeredApproachTheoperatingAnOperatingSystemLayerOperatingSystemAnOperatingSystemLayerOperaMicrokernelSystemStructureMovesasmuchfromthekernelinto“user”space.Communicationtakesplacebetweenusermodulesusingmessagepassing.Benefits: -easiertoextendamicrokernel（微内核） -easiertoporttheoperatingsystemtonewarchitectures -morereliable(lesscodeisrunninginkernelmode) -moresecureOperatingSystemMicrokernelSystemStructureMVirtualMachinesAvirtualmachinetakesthelayeredapproachtoitslogicalconclusion.Ittreatshardwareandtheoperatingsystemkernelasthoughtheywereallhardware.Avirtualmachineprovidesaninterfaceidenticaltotheunderlyingbarehardware.Theoperatingsystemcreatestheillusionofmultipleprocesses,eachexecutingonitsownprocessorwithitsown(virtual)memory.OperatingSystemVirtualMachinesAvirtualmachVirtualMachines(Cont.)Theresourcesofthephysicalcomputeraresharedtocreatethevirtualmachines.CPUschedulingcancreatetheappearancethatusershavetheirownprocessor.Spoolingandafilesystemcanprovidevirtualcardreadersandvirtuallineprinters.Anormalusertime-sharingterminalservesasthevirtualmachineoperator’sconsole.OperatingSystemVirtualMachines(Cont.)ThereSystemModelsNon-virtualMachineVirtualMachineOperatingSystemSystemModelsNon-virtualMachiAdvantages/DisadvantagesofVirtualMachinesThevirtual-machineconceptprovidescompleteprotectionofsystemresourcessinceeachvirtualmachineisisolatedfromallothervirtualmachines.Thisisolation,however,permitsnodirectsharingofresources.OperatingSystemAdvantages/DisadvantagesofViAvirtual-machinesystemisaperfectvehicleforoperating-systemsresearchanddevelopment.Systemdevelopmentisdoneonthevirtualmachine,insteadofonaphysicalmachineandsodoesnotdisruptnormalsystemoperation.Thevirtualmachineconceptisdifficulttoimplementduetotheeffortrequiredtoprovideanexactduplicatetotheunderlyingmachine.OperatingSystemAvirtual-machinesystemisaJavaVirtualMachineCompiledJavaprogramsareplatform-neutralbytecodesexecutedbyaJavaVirtualMachine(JVM).JVMconsistsof -classloader -classverifier -runtimeinterpreterJust-In-Time(JIT)compilersincreaseperformanceOperatingSystemJavaVirtualMachineCompiledJJavaVirtualMachineOperatingSystemJavaVirtualMachineOperatingSystemDesignGoalsUsergoals–operatingsystemshouldbeconvenienttouse,easytolearn,reliable,safe,andfast.Systemgoals–operatingsystemshouldbeeasytodesign,implement,andmaintain,aswellasflexible,reliable,error-free,andefficient.OperatingSystemSystemDesignGoalsUsergoalsMechanismsandPoliciesMechanismsdeterminehowtodosomething,policiesdecidewhatwillbedone.Theseparationofpolicyfrommechanismisaveryimportantprinciple,itallowsmaximumflexibilityifpolicydecisionsaretobechangedlater.OperatingSystemMechanismsandPoliciesMechaniSystemImplementationTraditionallywritteninassemblylanguage,operatingsystemscannowbewritteninhigher-levellanguages.Codewritteninahigh-levellanguage:canbewrittenfaster.ismorecompact.iseasiertounderstandanddebug.Anoperatingsystemisfareasiertoport(movetosomeotherhardware)ifitiswritteninahigh-levellanguage.OperatingSystemSystemImplementationTraditionSystemGeneration(SYSGEN)Operatingsystemsaredesignedtorunonanyofaclassofmachines;thesystemmustbeconfiguredforeachspecificcomputersite.SYSGENprogramobtainsinformationconcerningthespecificconfigurationofthehardwaresystem.Booting–startingacomputerbyloadingthekernel.Bootstrapprogram–codestoredinROMthatisabletolocatethekernel,loaditintomemory,andstartitsexecution.OperatingSystemSystemGeneration(SYSGEN)Oper13.13OperatingSystem3.7OperatingSystemChapter3:Operating-SystemStructuresSystemComponentsOperatingSystemServicesSystemCallsSystemProgramsSystemStructureVirtualMachinesSystemDesignandImplementationSystemGenerationOperatingSystemChapter3:Operating-SystemSCommonSystemComponentsProcessManagementMainMemoryManagementFileManagementI/OSystemManagementSecondaryManagementNetworkingProtectionSystemCommand-InterpreterSystemOperatingSystemCommonSystemComponentsProcesProcessManagementAprocessisaprograminexecution.Aprocessneedscertainresources,includingCPUtime,memory,files,andI/Odevices,toaccomplishitstask.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithprocessmanagement.Pcesssuspensionandresumption.Provisionofmechanismsfor:processsynchronizationprocesscommunicationOperatingSystemProcessManagementAprocessisMain-MemoryManagementMemoryisalargearrayofwordsorbytes,eachwithitsownaddress.ItisarepositoryofquicklyaccessibledatasharedbytheCPUandI/Odevices.Mainmemoryisavolatilestoragedevice.Itlosesitscontentsinthecaseofsystemfailure.OperatingSystemMain-MemoryManagementMemoryiTheoperatingsystemisresponsibleforthefollowingactivitiesinconnectionswithmemorymanagement:Keeptrackofwhichpartsofmemoryarecurrentlybeingusedandbywhom.Decidewhichprocessestoloadwhenmemoryspacebecomesavailable.Allocateanddeallocatememoryspaceasneeded.OperatingSystemTheoperatingsystemisresponFileManagementAfileisacollectionofrelatedinformationdefinedbyitscreator.Commonly,filesrepresentprograms(bothsourceandobjectforms)anddata.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionswithfilemanagement:Filecreationanddeletion.Directorycreationanddeletion.Supportofprimitivesformanipulatingfilesanddirectories.Mappingfilesontosecondarystorage.Filebackuponstable(nonvolatile)storagemedia.OperatingSystemFileManagementAfileisacolI/OSystemManagementTheI/Osystemconsistsof:Abuffer-cachingsystemAgeneraldevice-driverinterfaceDriversforspecifichardwaredevicesOperatingSystemI/OSystemManagementTheI/OsSecondary-StorageManagementSincemainmemory(primarystorage)isvolatileandtoosmalltoaccommodatealldataandprogramspermanently,thecomputersystemmustprovidesecondarystoragetobackupmainmemory.OperatingSystemSecondary-StorageManagementSiMostmoderncomputersystemsusedisksastheprincipleon-linestoragemedium,forbothprogramsanddata.Theoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithdiskmanagement:FreespacemanagementStorageallocationDiskschedulingOperatingSystemMostmoderncomputersystemsuCommand-InterpreterSystemManycommandsaregiventotheoperatingsystembycontrolstatementswhichdealwith:processcreationandmanagementI/Ohandlingsecondary-storagemanagementmain-memorymanagementfile-systemaccessprotectionnetworkingOperatingSystemCommand-InterpreterSystemManyCommand-InterpreterSystem(Cont.)Theprogramthatreadsandinterpretscontrolstatementsiscalledvariously:command-lineinterpretershell(inUNIX)

Itsfunctionistogetandexecutethenextcommandstatement.OperatingSystemCommand-InterpreterSystem(CoOperatingSystemServicesProgramexecution–systemcapabilitytoloadaprogramintomemoryandtorunit.I/Ooperations–sinceuserprogramscannotexecuteI/Ooperationsdirectly,theoperatingsystemmustprovidesomemeanstoperformI/O.File-systemmanipulation–programcapabilitytoread,write,create,anddeletefiles.OperatingSystemOperatingSystemServicesProgrCommunications–exchangeofinformationbetweenprocessesexecutingeitheronthesamecomputerorondifferentsystemstiedtogetherbyanetwork.Implementedviasharedmemoryormessagepassing.Errordetection–ensurecorrectcomputingbydetectingerrorsintheCPUandmemoryhardware,inI/Odevices,orinuserprograms.OperatingSystemCommunications–exchangeofiAdditionalOperatingSystemFunctionsAdditionalfunctionsexistnotforhelpingtheuser,butratherforensuringefficientsystemoperations.Resourceallocation–allocatingresourcestomultipleusersormultiplejobsrunningatthesametime.Accounting–keeptrackofandrecordwhichusersusehowmuchandwhatkindsofcomputerresourcesforaccountbillingorforaccumulatingusagestatistics.Protection–ensuringthatallaccesstosystemresourcesiscontrolled.OperatingSystemAdditionalOperatingSystemFuSystemCallsSystemcallsprovidetheinterfacebetweenarunningprogramandtheoperatingsystem.Generallyavailableasassembly-languageinstructions.Languagesdefinedtoreplaceassemblylanguageforsystemsprogrammingallowsystemcallstobemadedirectly(e.g.,C,C++)OperatingSystemSystemCallsSystemcallsproviThreegeneralmethodsareusedtopassparametersbetweenarunningprogramandtheoperatingsystem.Passparametersinregisters.Storetheparametersinatableinmemory,andthetableaddressispassedasaparameterinaregister.Push(store)theparametersontothestackbytheprogram,andpopoffthestackbyoperatingsystem.OperatingSystemThreegeneralmethodsareusedPassingofParametersAsATableOperatingSystemPassingofParametersAsATabTypesofSystemCallsProcesscontrolFilemanagementDevicemanagementInformationmaintenanceCommunicationsOperatingSystemTypesofSystemCallsProcesscMS-DOSExecutionAtSystemStart-upRunningaProgramOperatingSystemMS-DOSExecutionAtSystemStarUNIXRunningMultipleProgramsOperatingSystemUNIXRunningMultipleProgramsCommunicationModelsMsgPassingSharedMemoryCommunicationmaytakeplaceusingeithermessagepassingorsharedmemory.OperatingSystemCommunicationModelsMsgPassinSystemProgramsSystemprogramsprovideaconvenientenvironmentforprogramdevelopmentandexecution.Thecanbedividedinto:FilemanipulationStatusinformationFilemodificationProgramminglanguagesupportProgramloadingandexecutionCommunicationsApplicationprogramsMostusers’viewoftheoperationsystemisdefinedbysystemprograms,nottheactualsystemcalls.

OperatingSystemSystemProgramsSystemprogramsMS-DOSSystemStructureMS-DOS–writtentoprovidethemostfunctionalityintheleastspacenotdividedintomodulesAlthoughMS-DOShassomestructure,itsinterfacesandlevelsoffunctionalityarenotwellseparatedOperatingSystemMS-DOSSystemStructureMS-DOSMS-DOSLayerStructureOperatingSystemMS-DOSLayerStructureOperatinUNIXSystemStructure

UNIX–limitedbyhardwarefunctionality,theoriginalUNIXoperatingsystemhadlimitedstructuring.TheUNIXOSconsistsoftwoseparableparts.SystemsprogramsThekernelConsistsofeverythingbelowthesystem-callinterfaceandabovethephysicalhardwareProvidesthefilesystem,CPUscheduling,memorymanagement,andotheroperating-systemfunctions;alargenumberoffunctionsforonelevel.OperatingSystemUNIXSystemStructureUNIX–lUNIXSystemStructureOperatingSystemUNIXSystemStructureOperatingLayeredApproachTheoperatingsystemisdividedintoanumberoflayers(levels),eachbuiltontopoflowerlayers.Thebottomlayer(layer0),isthehardware;thehighest(layerN)istheuserinterface.Withmodularity,layersareselectedsuchthateachusesfunctions(operations)andservicesofonlylower-levellayers.OperatingSystemLayeredApproachTheoperatingAnOperatingSystemLayerOperatingSystemAnOperatingSystemLayerOperaMicrokernelSystemStructureMovesasmuchfromthekernelinto“user”space.Communicationtakesplacebetweenusermodulesusingmessagepassing.Benefits: -easiertoextendamicrokernel（微内核） -easiertoporttheoperatingsystemtonewarchitectures -morereliable(lesscodeisrunninginkernelmode) -moresecureOperatingSystemMicrokernelSystemStructureMVirtualMachinesAvirtualmachinetakesthelayeredapproachtoitslogicalconclusion.Ittreatshardwareandtheoperatingsystemkernelasthoughtheywereallhardware.Avirtualmachineprovidesaninterfaceidenticaltotheunderlyingbarehardware.Theoperatingsystemcreatestheillusionofmultipleprocesses,eachexecutingonitsownprocessorwithitsown(virtual)memory.OperatingSystemVirtualMachinesAvirtualmachVirtualMachines(Cont.)Theresourcesofthephysicalcomputeraresharedtocreatethevirtualmachines.CPUschedulingcancreatetheappearancethatusershavetheirownprocessor.Spoolingandafilesystemcanprovidevirtualcardreadersandvirtuallineprinters.Anormalusertime-sharingterminalservesasthevirtualmachineoperator’sconsole.OperatingSystemVirtualMachines(Cont.)ThereSystemModelsNon-virtualMachineVirtualMachineOperatingSystemSystemModelsNon-virtualMachiAdvantages/DisadvantagesofVirtualMachinesThevirtual-machineconceptprovidescompleteprotectionofsystemresourcessinceeachvirtualmachineisisolatedfromallothervirtualmachines.Thisisolation,however,permitsnodirectsharingofresources.Operat