Chapter1:IntroductionTheBookOperatingSystemConcepts–7thEdition,Jan12,20051.2Silberschatz,GalvinandGagne?2005Gradingpolicy

期中考核成績（10%）課程項目成績（10%）課后作業(yè)成績（10%）考勤成績（10%）實驗成績（20%）期末考試成績（40%）OperatingSystemConcepts–7thEdition,Jan12,20051.3Silberschatz,GalvinandGagne?2005Objectives

Toprovideagrandtourofthemajoroperatingsystemscomponents

ToinfluenceComputationalThinkingOperatingSystemConcepts–7thEdition,Jan12,20051.4Silberschatz,GalvinandGagne?2005WhatisanOperatingSystem?

Aprogramthatactsasanintermediarybetweenauserofacomputerandthecomputerhardware.

Operatingsystemgoals:

Executeuserprogramsandmakesolvinguserproblemseasier.

Makethecomputersystemconvenienttouse.

Usethecomputerhardwareinanefficientmanner.OperatingSystemConcepts–7thEdition,Jan12,20051.5Silberschatz,GalvinandGagne?2005ComputerSystemStructure

Computersystemcanbedividedintofourcomponents

Hardware–providesbasiccomputingresources

CPU,memory,I/Odevices

Operatingsystem

Controlsandcoordinatesuseofhardwareamongvariousapplicationsandusers

Applicationprograms–definethewaysinwhichthesystemresourcesareusedtosolvethecomputingproblemsoftheusers

Wordprocessors,compilers,webbrowsers,databasesystems,videogames

Users

People,machines,othercomputersOperatingSystemConcepts–7thEdition,Jan12,20051.6Silberschatz,GalvinandGagne?2005FourComponentsofaComputerSystemOperatingSystemConcepts–7thEdition,Jan12,20051.7Silberschatz,GalvinandGagne?2005OperatingSystemDefinition

OSisaresourceallocator

ManagesallresourcesDecidesbetweenconflictingrequestsforefficientandfairresourceuse

OSisacontrolprogram

ControlsexecutionofprogramstopreventerrorsandimproperuseofthecomputerOperatingSystemConcepts–7thEdition,Jan12,20051.8Silberschatz,GalvinandGagne?2005OperatingSystemDefinition(Cont.)

Nouniversallyaccepteddefinition

“Everythingavendorshipswhenyouorderanoperatingsystem”isgoodapproximation

Butvarieswildly

“Theoneprogramrunningatalltimesonthecomputer”isthekernel.Everythingelseiseitherasystemprogram(shipswiththeoperatingsystem)oranapplicationprogramOperatingSystemConcepts–7thEdition,Jan12,20051.9Silberschatz,GalvinandGagne?2005ComputerSystemOrganization

Computer-systemoperation

OneormoreCPUs,devicecontrollersconnectthroughcommonbusprovidingaccesstosharedmemoryConcurrentexecutionofCPUsanddevicescompetingformemorycycles

OperatingSystemConcepts–7thEdition,Jan12,20051.10Silberschatz,GalvinandGagne?2005ComputerStartup

bootstrapprogramisloadedatpower-uporreboot

TypicallystoredinROMorEEPROM,generallyknownasfirmware

Initializatesallaspectsofsystem

LoadsoperatingsystemkernelandstartsexecutionOperatingSystemConcepts–7thEdition,Jan12,20051.11Silberschatz,GalvinandGagne?2005Computer-SystemI/OOperation

I/OdevicesandtheCPUcanexecuteconcurrently.

Eachdevicecontrollerisinchargeofaparticulardevicetype.

Eachdevicecontrollerhasalocalbuffer.

CPUmovesdatafrom/tomainmemoryto/fromlocalbuffers

DevicecontrollerinformsCPUthatithasfinisheditsoperationbycausinganinterrupt.OperatingSystemConcepts–7thEdition,Jan12,20051.12Silberschatz,GalvinandGagne?2005CommonFunctionsofInterrupts

Interrupttransferscontroltotheinterruptserviceroutinegenerally,throughtheinterruptvector,whichcontainstheaddressesofalltheserviceroutines.

Interruptarchitecturemustsavetheaddressoftheinterruptedinstruction.

Incominginterruptsaredisabledwhileanotherinterruptisbeingprocessedtopreventalostinterrupt.

Atrapisasoftware-generatedinterruptcausedeitherbyanerrororauserrequest.

Anoperatingsystemisinterruptdriven.OperatingSystemConcepts–7thEdition,Jan12,20051.13Silberschatz,GalvinandGagne?2005InterruptHandling

TheoperatingsystempreservesthestateoftheCPUbystoringregistersandtheprogramcounter.

Determineswhichtypeofinterrupthasoccurred:

polling

vectoredinterruptsystem

SeparatesegmentsofcodedeterminewhatactionshouldbetakenforeachtypeofinterruptOperatingSystemConcepts–7thEdition,Jan12,20051.14Silberschatz,GalvinandGagne?2005InterruptTimelineOperatingSystemConcepts–7thEdition,Jan12,20051.15Silberschatz,GalvinandGagne?2005StorageStructure

Mainmemory–onlylargestoragemediathattheCPUcanaccessdirectly.Secondarystorage–extensionofmainmemorythatprovideslargenonvolatilestoragecapacity.Magneticdisks–rigidmetalorglassplatterscoveredwithmagneticrecordingmaterial

Disksurfaceislogicallydividedintotracks,whicharesubdividedintosectors.Thediskcontrollerdeterminesthelogicalinteractionbetweenthedeviceandthecomputer.

OperatingSystemConcepts–7thEdition,Jan12,20051.16Silberschatz,GalvinandGagne?2005StorageHierarchy

Storagesystemsorganizedinhierarchy.

SpeedCostVolatility

OperatingSystemConcepts–7thEdition,Jan12,20051.17Silberschatz,GalvinandGagne?2005Storage-DeviceHierarchyOperatingSystemConcepts–7thEdition,Jan12,20051.18Silberschatz,GalvinandGagne?2005RegisterOperatingSystemConcepts–7thEdition,Jan12,20051.19Silberschatz,GalvinandGagne?2005Caching

Importantprinciple,performedatmanylevelsinacomputer(inhardware,operatingsystem,software)InformationinusecopiedfromslowertofasterstoragetemporarilyFasterstorage(cache)checkedfirsttodetermineifinformationisthere

Ifitis,informationuseddirectlyfromthecache(fast)Ifnot,datacopiedtocacheandusedthere

Cachesmallerthanstoragebeingcached

CachemanagementimportantdesignproblemCachesizeandreplacementpolicyMainmemorycanbeviewedasalastcacheforsecondarystorage.

OperatingSystemConcepts–7thEdition,Jan12,20051.20Silberschatz,GalvinandGagne?2005PerformanceofVariousLevelsofStorage

MovementbetweenlevelsofstoragehierarchycanbeexplicitorimplicitOperatingSystemConcepts–7thEdition,Jan12,20051.21Silberschatz,GalvinandGagne?2005MigrationofIntegerAfromDisktoRegister

Multitaskingenvironmentsmustbecarefultousemostrecentvalue,notmatterwhereitisstoredinthestoragehierarchy

MultiprocessorenvironmentmustprovidecachecoherencyinhardwaresuchthatallCPUshavethemostrecentvalueintheircacheDistributedenvironmentsituationevenmorecomplex

SeveralcopiesofadatumcanexistVarioussolutionscoveredinChapter17

OperatingSystemConcepts–7thEdition,Jan12,20051.22Silberschatz,GalvinandGagne?2005I/OStructure

AlargeportionofoperatingsystemcodeisdedicatedtomanagingI/O.Ageneral-purposecomputersystemconsistsofCPUsandmultipledevicecontrollersthatareconnectedthroughacommonbus.Eachdevicecontrollerisinchargeofaspecifictypeofdevice.Dependingonthecontroller,theremaybemorethanoneattacheddevice.Adevicecontrollermaintainssomelocalbufferstorageandasetofspecial-purposeregisters.

OperatingSystemConcepts–7thEdition,Jan12,20051.23Silberschatz,GalvinandGagne?2005I/OStructure

Thedevicecontrollerisresponsibleformovingthedatabetweentheperipheraldevicesthatitcontrolsanditslocalbufferstorage.Typically,operatingsystemshaveadevicedriverforeachdevicecontroller.Thisdevicedriverunderstandsthedevicecontrollerandpresentsauniforminterfacetohedevicetotherestoftheoperatingsystem.

OperatingSystemConcepts–7thEdition,Jan12,20051.24Silberschatz,GalvinandGagne?2005Interrupt

Thecontrollerstartsthetransferofdatafromthedevicetoitslocalbuffer.Oncethetransferofdataiscomplete,thedevicecontrollerinformsthedevicedriverviaaninterruptthatithasfinisheditsoperation.OperatingSystemConcepts–7thEdition,Jan12,20051.25Silberschatz,GalvinandGagne?2005DirectMemoryAccess(DMA)

Aftersettingupbuffers,pointers,andcountersfortheI/Odevice,thedevicecontrollertransfersanentireblockofdatadirectlytoorfromitsownbufferstoragetomemory,withnointerventionbytheCPU.

Onlyoneinterruptisgeneratedperblock,totellthedevicedriverthattheoperationhascompleted.OperatingSystemConcepts–7thEdition,Jan12,20051.26Silberschatz,GalvinandGagne?2005Computer-SystemArchitecture

Single-ProcessorSystemsMultiprocessorSystems

threemainadvantages:

Increasedthroughput.

Economyofscale.

Increasedreliability

asymmetricmultiprocessingandsymmetricmultiprocessing(SMP)

ClusteredSystemsOperatingSystemConcepts–7thEdition,Jan12,20051.27Silberschatz,GalvinandGagne?2005OperatingSystemStructure

Multiprogrammingneededforefficiency

SingleusercannotkeepCPUandI/OdevicesbusyatalltimesMultiprogrammingorganizesjobs(codeanddata)soCPUalwayshasonetoexecuteAsubsetoftotaljobsinsystemiskeptinmemoryOnejobselectedandrunviajobschedulingWhenithastowait(forI/Oforexample),OSswitchestoanotherjob

Timesharing(multitasking)islogicalextensioninwhichCPUswitchesjobssofrequentlythatuserscaninteractwitheachjobwhileitisrunning,creatinginteractivecomputing

Responsetimeshouldbe<1secondEachuserhasatleastoneprogramexecutinginmemoryprocessIfseveraljobsreadytorunatthesametimeCPUschedulingIfprocessesdon’tfitinmemory,swappingmovestheminandouttorunVirtualmemoryallowsexecutionofprocessesnotcompletelyinmemory

OperatingSystemConcepts–7thEdition,Jan12,20051.28Silberschatz,GalvinandGagne?2005MemoryLayoutforMultiprogrammedSystemOperatingSystemConcepts–7thEdition,Jan12,20051.29Silberschatz,GalvinandGagne?2005Operating-SystemOperations

InterruptdrivenbyhardwareSoftwareerrororrequestcreatesexceptionortrap

Divisionbyzero,requestforoperatingsystemservice

Otherprocessproblemsincludeinfiniteloop,processesmodifyingeachotherortheoperatingsystemDual-modeoperationallowsOStoprotectitselfandothersystemcomponents

UsermodeandkernelmodeModebitprovidedbyhardware

Providesabilitytodistinguishwhensystemisrunningusercodeorkernelcode

Someinstructionsdesignatedasprivileged,onlyexecutableinkernelmode

Systemcallchangesmodetokernel,returnfromcallresetsittouserOperatingSystemConcepts–7thEdition,Jan12,20051.30Silberschatz,GalvinandGagne?2005TransitionfromUsertoKernelModeOperatingSystemConcepts–7thEdition,Jan12,20051.31Silberschatz,GalvinandGagne?2005Timer

Timertopreventinfiniteloop/processhoggingresources

SetinterruptafterspecificperiodOperatingsystemdecrementscounterWhencounterzerogenerateaninterruptSetupbeforeschedulingprocesstoregaincontrolorterminateprogramthatexceedsallottedtime

OperatingSystemConcepts–7thEdition,Jan12,20051.32Silberschatz,GalvinandGagne?2005ProcessManagement

Aprocessisaprograminexecution.Itisaunitofworkwithinthesystem.Programisapassiveentity,processisanactiveentity.Processneedsresourcestoaccomplishitstask

CPU,memory,I/O,filesInitializationdata

ProcessterminationrequiresreclaimofanyreusableresourcesSingle-threadedprocesshasoneprogramcounterspecifyinglocationofnextinstructiontoexecute

Processexecutesinstructionssequentially,oneatatime,untilcompletion

Multi-threadedprocesshasoneprogramcounterperthreadTypicallysystemhasmanyprocesses,someuser,someoperatingsystemrunningconcurrentlyononeormoreCPUs

ConcurrencybymultiplexingtheCPUsamongtheprocesses/threadsOperatingSystemConcepts–7thEdition,Jan12,20051.33Silberschatz,GalvinandGagne?2005ProcessManagementActivitiesTheoperatingsystemisresponsibleforthefollowingactivitiesinconnectionwithprocessmanagement:CreatinganddeletingbothuserandsystemprocessesSuspendingandresumingprocessesProvidingmechanismsforprocesssynchronizationProvidingmechanismsforprocesscommunicationProvidingmechanismsfordeadlockhandling

OperatingSystemConcepts–7thEdition,Jan12,20051.34Silberschatz,GalvinandGagne?2005MemoryManagement

AlldatainmemorybeforeandafterprocessingAllinstructionsinmemoryinordertoexecuteMemorymanagementdetermineswhatisinmemorywhen

OptimizingCPUutilizationandcomputerresponsetousers

Memorymanagementactivities

KeepingtrackofwhichpartsofmemoryarecurrentlybeingusedandbywhomDecidingwhichprocesses(orpartsthereof)anddatatomoveintoandoutofmemoryAllocatinganddeallocatingmemoryspaceasneeded

OperatingSystemConcepts–7thEdition,Jan12,20051.35Silberschatz,GalvinandGagne?2005File-SystemManagement

OSprovidesuniform,logicalviewofinformationstorage

Abstractsphysicalpropertiestologicalstorageunit-fileEachmediumiscontrolledbydevice(i.e.,diskdrive,tapedrive)

Varyingpropertiesincludeaccessspeed,capacity,data-transferrate,accessmethod(sequentialorrandom)

File-Systemmanagement

FilesusuallyorganizedintodirectoriesAccesscontrolonmostsystemstodeterminewhocanaccesswhatOSactivitiesinclude

Creatinganddeletingfilesanddirectories

Primitivestomanipulatefilesanddirs

Mappingfilesontosecondarystorage

Backupfilesontostable(non-volatile)storagemediaOperatingSystemConcepts–7thEdition,Jan12,20051.36Silberschatz,GalvinandGagne?2005Mass-StorageManagement

Usuallydisksusedtostoredatathatdoesnotfitinmainmemoryordatathatmustbekeptfora“l(fā)ong”periodoftime.PropermanagementisofcentralimportanceEntirespeedofcomputeroperationhingesondisksubsystemanditsalgorithmsOSactivities

Free-spacemanagementStorageallocationDiskscheduling

Somestorageneednotbefast

Tertiarystorageincludesopticalstorage,magnetictapeStillmustbemanagedVariesbetweenWORM(write-once,read-many-times)andRW(read-write)

OperatingSystemConcepts–7thEdition,Jan12,20051.37Silberschatz,GalvinandGagne?2005I/OSubsystem

OnepurposeofOSistohidepeculiaritiesofhardwaredevicesfromtheuserI/Osubsystemresponsiblefor

MemorymanagementofI/Oincludingbuffering(storingdatatemporarilywhileitisbeingtransferred),caching(storingpartsofdatainfasterstorageforperformance),spooling(theoverlappingofoutputofonejobwithinputofotherjobs)Generaldevice-driverinterfaceDriversforspecifichardwaredevices

OperatingSystemConcepts–7thEdition,Jan12,20051.38Silberschatz,GalvinandGagne?2005ProtectionandSecurity

Protection–anymechanismforcontrollingaccessofprocessesoruserstoresourcesdefinedbytheOSSecurity–defenseofthesystemagainstinternalandexternalattacks

Hugerange,includingdenial-of-service,worms,viruses,identitytheft,theftofservice

Systemsgenerallyfirstdistinguishamongusers,todeterminewhocandowhat

Useridentities(userIDs,securityIDs)includenameandassociatednumber,oneperuserUserIDthenassociatedwithallfiles,processesofthatusertodetermineaccesscontrolGroupidentifier(groupID)allowssetofuserstobedefinedandcontrolsmanaged,thenalsoassociatedwitheachprocess,filePrivilegeescalationallowsusertochangetoeffectiveIDwithmorerights

OperatingSystemConcepts–7thEdition,Jan12,20051.39Silberschatz,GalvinandGagne?2005DistributedSystems

Adistributedsystemisacollectionofphysicallyseparate,possiblyheterogeneouscomputersystemsthatarenetworkedtoprovidetheuserswithaccesstothevariousresourcesthatthesystemmaintains.OperatingSystemConcepts–7thEdition,Jan12,20051.40Silberschatz,GalvinandGagne?2005Special-PurposeSystems

Real-TimeEmbeddedSystems

MultimediaSystems

HandheldSystemsOperatingSystemConcepts–7thEdition,Jan12,20051.41Silberschatz,GalvinandGagne?2005Summary

Anoperatingsystemissoftwarethatmanagesthecomputerhardwareaswellasprovidinganenvironmentforapplicationprogramstorun.MainmemoryistheonlylargestorageareathattheprocessorcanaccessdirectlyMostcomputersystemsprovidesecondarystorageasanextensionofmainmemory.Secondarystorageprovidesaformofnonvolatilestoragethatiscapableofholdinglargequantitiesofdatapermanently.Thewidevarietyofstoragesystemsinacomputersystemcanbeorganizedinahierarchyaccordingtospeedandcost.Whereastheaccesstimegenerallyincreases.

OperatingSystemConcepts–7thEdition,Jan12,20051.42Silberschatz,GalvinandGagne?2005Summary

Thereareseveraldifferentstrategiesfordesigningacomputersystem.Uniprocessorsystemshaveonlyasingleprocessorwhilemultiprocessorsystemscontaintwoormoreprocessorsthatsharephysicalmemoryandperipheraldevices.Themostcommonmultiprocessordesignissymmetricmultiprocessing(orSMP),whereallprocessorsareconsideredpeersandrunindependentlyofoneanother.Clusteredsystemsareaspecializedformofmultiprocessorsystemsandconsistof