操作系統(tǒng)原理英文版課件：Chapter 2 Computer-System Structures

Chapter2:Computer-SystemStructures(6thEdition)OperatingSystemConceptsChapter2Computer-SystemStructures(6thEd.)ComputerSystemOperationI/OStructureStorageStructureStorageHierarchyHardwareProtectionNetworkStructureOperatingSystemConceptsComputer-SystemArchitectureHowdoestheOSgetintosystem?Howdowerequestforservices?HowdoestheOSknowsomethinghashappened?HowOSgetsintosystemOperatingSystemConceptsOperatingSystemConceptsHowLinuxgetsintosystemOperatingSystemConceptsComputer-SystemOperationI/OdevicesandtheCPUcanexecuteconcurrently.Eachdevicecontrollerisinchargeofaparticulardevicetype.Eachdevicecontrollerhasalocalbuffer.OperatingSystemConceptsComputer-SystemOperation(Cont.)CPUmovesdatafrom/tomainmemoryto/fromlocalbuffersI/Oisfromthedevicetolocalbufferofcontroller.DevicecontrollerinformsCPUthatithasfinisheditsoperationbycausinganinterrupt.WhyweneedInterrupt?OperatingSystemConceptsInterruptAneventthatrequirestheattentionoftheOSisaninterrupt.TheseeventsincludethecompletionofanI/O,akeypress,arequestforservice,adivisionbyzeroandsoon.Interruptsmaybegeneratedbyhardwareorsoftware.Aninterruptgeneratedbysoftware(i.e.,divisionby0)isusuallyreferredtoasatrap.Modernoperatingsystemsareinterruptdriven,meaningtheOSisinactiononlyifaninterruptoccurs.OperatingSystemConceptsWhatisInterruptdriven?TheOSisactivatedbyaninterrupt.Theexecutingprogramissuspended.ControlistransferredtotheOS.ProgramcontinueswhentheservicecompletesOperatingSystemConceptsInterruptTimeLineForaSingleProcessDoingOutputPleasesomeoneexplainthis.OperatingSystemConceptsCommonFunctionsofInterruptsInterrupttransferscontroltotheinterruptserviceroutinegenerally,throughtheinterruptvector,whichcontainstheaddressesofalltheserviceroutines.Interruptarchitecturemustsavetheaddressoftheinterruptedinstruction.Incominginterruptsaredisabledwhileanotherinterruptisbeingprocessedtopreventalostinterrupt.OperatingSystemConceptsInterruptHandlingTheoperatingsystempreservesthestateoftheCPUbystoringregistersandtheprogramcounter.Determineswhichtypeofinterrupthasoccurred:Polling(software)vectoredinterruptsystem(hardware)SeparatesegmentsofcodedeterminewhatactionshouldbetakenforeachtypeofinterruptOperatingSystemConceptsI/OInterruptOperatingSystemConceptsI/OStructure(Cont.)AfterI/Ostarts,controlreturnstouserprogramwithoutwaitingforI/Ocompletion.Systemcall–requesttotheoperatingsystemtoallowusertowaitforI/Ocompletion.Device-statustablecontainsentryforeachI/Odeviceindicatingitstype,address,andstate.OperatingsystemindexesintoI/Odevicetabletodeterminedevicestatusandtomodifytableentrytoincludeinterrupt.OperatingSystemConceptsTwoI/OMethodsSynchronousAsynchronousOperatingSystemConceptsDevice-StatusTableOperatingSystemConceptsDirectMemoryAccessStructureUsedforhigh-speedI/Odevicesabletotransmitinformationatclosetomemoryspeeds.DevicecontrollertransfersblocksofdatafrombufferstoragedirectlytomainmemorywithoutCPUintervention.Onlyoneinterruptisgeneratedperblock,ratherthantheoneinterruptperbyte.OperatingSystemConceptsDirectMemoryAccessStructure(Cont.)OperatingSystemConceptsStorageStructureMainmemory–onlylargestoragemediathattheCPUcanaccessdirectly.Secondarystorage–extensionofmainmemorythatprovideslargenonvolatilestoragecapacity.Magneticdisks–rigidmetalorglassplatterscoveredwithmagneticrecordingmaterialDisksurfaceislogicallydividedintotracks,whicharesubdividedintosectors.Thediskcontrollerdeterminesthelogicalinteractionbetweenthedeviceandthecomputer.OperatingSystemConceptsMoving-HeadDiskMechanismOperatingSystemConceptsStorageHierarchyStoragesystemsorganizedinhierarchy.SpeedCostVolatilityCaching–copyinginformationintofasterstoragesystem;mainmemorycanbeviewedasalastcacheforsecondarystorage.OperatingSystemConceptsStorage-DeviceHierarchyOperatingSystemConceptsCachingUseofhigh-speedmemorytoholdrecently-accesseddata.Requiresacachemanagementpolicy.Cachingintroducesanotherlevelinstoragehierarchy.Thisrequiresdatathatissimultaneouslystoredinmorethanoneleveltobeconsistent.OperatingSystemConceptsMigrationofAFromDisktoRegisterOperatingSystemConceptsHardwareProtectionDual-ModeOperationI/OProtectionMemoryProtectionCPUProtectionOperatingSystemConceptsDual-ModeOperationSharingsystemresourcesrequiresoperatingsystemtoensurethatanincorrectprogramcannotcauseotherprogramstoexecuteincorrectly.Providehardwaresupporttodifferentiatebetweenatleasttwomodesofoperations.1. Usermode–executiondoneonbehalfofauser.(用戶態(tài)或目態(tài))2. Monitormode(alsokernelmodeorsystemmode)–executiondoneonbehalfofoperatingsystem.(核心態(tài)或管態(tài))OperatingSystemConceptsDual-ModeOperation(Cont.)Modebitaddedtocomputerhardwaretoindicatethecurrentmode:monitor(0)oruser(1).Whenaninterruptorfaultoccurshardwareswitchestomonitormode.Privilegedinstructionscanbeissuedonlyinmonitormode.monitoruserInterrupt/faultsetusermodeOperatingSystemConceptsOperatingSystemConceptsI/OProtectionAllI/Oinstructionsareprivilegedinstructions（特權(quán)指令）.Mustensurethatauserprogramcouldnevergaincontrolofthecomputerinmonitormode(I.e.,auserprogramthat,aspartofitsexecution,storesanewaddressintheinterruptvector).OperatingSystemConceptsUseofASystemCalltoPerformI/OOperatingSystemConceptsMemoryProtectionMustprovidememoryprotectionatleastfortheinterruptvectorandtheinterruptserviceroutines.Inordertohavememoryprotection,addtworegistersthatdeterminetherangeoflegaladdressesaprogrammayaccess:Baseregister

（基址寄存器）–holdsthesmallestlegalphysicalmemoryaddress.Limitregister（界限寄存器）

–containsthesizeoftherangeMemoryoutsidethedefinedrangeisprotected.Operating