OperatingSystemConcepts

第二講計(jì)算機(jī)系統(tǒng)結(jié)構(gòu)本講主要內(nèi)容：計(jì)算機(jī)系統(tǒng)操作I/O結(jié)構(gòu)存儲(chǔ)系統(tǒng)的結(jié)構(gòu)分級(jí)的存儲(chǔ)體系硬件保護(hù)一般的系統(tǒng)結(jié)構(gòu)作業(yè)：第二章2,3,4,5,6,7,8,9,10OperatingSystemConcepts計(jì)算機(jī)系統(tǒng)結(jié)構(gòu)OperatingSystemConcepts計(jì)算機(jī)系統(tǒng)操作I/O設(shè)備和CPU可以并行地執(zhí)行。每一個(gè)設(shè)備控制器負(fù)責(zé)管理一種特定的設(shè)備。設(shè)備控制器通常都有本地的緩沖。CPUmovesdatafrom/tomainmemoryto/fromlocalbuffers。CPU需要在主存和設(shè)備控制器的本地緩沖之間傳送數(shù)據(jù)。I/Oisfromthedevicetolocalbufferofcontroller.I/O就是從設(shè)備到控制器的本地緩沖之間傳送數(shù)據(jù)。DevicecontrollerinformsCPUthatithasfinisheditsoperationbycausinganinterrupt.設(shè)備控制器在完成I/O操作后通過(guò)中斷通知CPU.OperatingSystemConceptsCommonFunctionsofInterrupts

中斷處理的公共操作Interrupttransferscontroltotheinterruptserviceroutinegenerally,throughtheinterruptvector,whichcontainstheaddressesofalltheserviceroutines.中斷一般來(lái)說(shuō)通過(guò)中斷向量將CPU的控制轉(zhuǎn)移給中斷服務(wù)程序。中斷向量包含有所有的服務(wù)程序的地址。Interruptarchitecturemustsavetheaddressoftheinterruptedinstruction.中斷處理的結(jié)構(gòu)要保存被中斷的指令的地址。inginterruptsaredisabledwhileanotherinterruptisbeingprocessedtopreventalostinterrupt.當(dāng)一個(gè)中斷被處理時(shí)，新進(jìn)來(lái)的中斷被關(guān)閉，以避免中斷請(qǐng)求丟失。Atrapisasoftware-generatedinterruptcausedeitherbyanerrororauserrequest.陷阱是由軟件產(chǎn)生的中斷，通常是由執(zhí)行指令的錯(cuò)誤或用戶的請(qǐng)求（執(zhí)行陷阱指令）產(chǎn)生的。Anoperatingsystemisinterruptdriven.操作系統(tǒng)都是中斷驅(qū)動(dòng)的。OperatingSystemConceptsInterruptHandling

中斷處理TheoperatingsystempreservesthestateoftheCPUbystoringregistersandtheprogramcounter.操作系統(tǒng)通過(guò)存儲(chǔ)寄存器和程序計(jì)數(shù)器來(lái)保存CPU的狀態(tài)。Determineswhichtypeofinterrupthasoccurred（決定中斷的類(lèi)型的方法）:Polling輪詢vectoredinterruptsystem中斷向量Separatesegmentsofcodedeterminewhatactionshouldbetakenforeachtypeofinterrupt單獨(dú)的代碼段決定對(duì)每一種中斷類(lèi)型要采取什么操作。OperatingSystemConceptsInterruptTimeLineForaSingleProcessDoingOutput

單個(gè)進(jìn)程做輸出操作的時(shí)序圖OperatingSystemConceptsI/OStructure

I/O結(jié)構(gòu)AfterI/Ostarts,controlreturnstouserprogramonlyuponI/Ocompletion.I/O操作開(kāi)始后，CPU的控制只有在I/O操作完成后才返回用戶程序。WaitinstructionidlestheCPUuntilthenextinterrupt等待指令在下一次中斷開(kāi)始之前使CPU處于空等狀態(tài)。Waitloop(contentionformemoryaccess).當(dāng)訪問(wèn)存儲(chǔ)器沖突時(shí)，就插入等待節(jié)拍。AtmostoneI/Orequestisoutstandingatatime,nosimultaneousI/Oprocessing.任何時(shí)候最多只有一個(gè)中斷請(qǐng)求處于處理狀態(tài)。AfterI/Ostarts,controlreturnstouserprogramwithoutwaitingforI/Ocompletion.I/O操作開(kāi)始后,CPU的控制不等I/O操作完成就交給用戶程序。Systemcall–requesttotheoperatingsystemtoallowusertowaitforI/Ocompletion.系統(tǒng)調(diào)用－請(qǐng)求操作系統(tǒng)容許用戶等待I/O完成。Device-statustablecontainsentryforeachI/Odeviceindicatingitstype,address,andstate.設(shè)備狀態(tài)表中每個(gè)I/O設(shè)備包含一個(gè)項(xiàng)目表明設(shè)備的類(lèi)型，地址和狀態(tài)。OperatingsystemindexesintoI/Odevicetabletodeterminedevicestatusandtomodifytableentrytoincludeinterrupt.操作系統(tǒng)訪問(wèn)I/O設(shè)備表決定設(shè)備的狀態(tài)，修改表項(xiàng)以加入中斷。OperatingSystemConceptsTwoI/OMethods

兩種方法Synchronous同步Asynchronous異步OperatingSystemConceptsDevice-StatusTable

設(shè)備狀態(tài)表OperatingSystemConceptsDirectMemoryAccessStructure

直接訪問(wèn)存儲(chǔ)器的結(jié)構(gòu)Usedforhigh-speedI/Odevicesabletotransmitinformationatclosetomemoryspeeds.用于高速I(mǎi)/O設(shè)備，以接近存儲(chǔ)器速度和、傳送信息。DevicecontrollertransfersblocksofdatafrombufferstoragedirectlytomainmemorywithoutCPUintervention.設(shè)備控制器不需要CPU的干預(yù)將一塊數(shù)據(jù)從緩沖直接傳送到存儲(chǔ)器。Onlyoninterruptisgeneratedperblock,ratherthantheoneinterruptperbyte.每個(gè)數(shù)據(jù)塊只產(chǎn)生一個(gè)中斷，而不是每個(gè)字節(jié)產(chǎn)生一個(gè)中斷。OperatingSystemConceptsStorageStructure

存儲(chǔ)結(jié)構(gòu)Mainmemory–onlylargestoragemediathattheCPUcanaccessdirectly.主存－CPU可以直接訪問(wèn)的存儲(chǔ)介質(zhì)。Secondarystorage–extensionofmainmemorythatprovideslargenonvolatilestoragecapacity.二級(jí)存儲(chǔ)器－主存的擴(kuò)展，提供大容量的永久存儲(chǔ)。Magneticdisks–rigidmetalorglassplatterscoveredwithmagneticrecordingmaterial磁盤(pán)－硬金屬或玻璃上覆蓋磁記錄材料。Disksurfaceislogicallydividedintotracks,whicharesubdividedintosectors.磁盤(pán)的表面從邏輯上分成磁道，磁道分為扇區(qū)。Thediskcontrollerdeterminesthelogicalinteractionbetweenthedeviceandthecomputer.磁盤(pán)控制器決定設(shè)備和計(jì)算機(jī)之間邏輯上相互作用。OperatingSystemConceptsMoving-HeadDiskMechanism

磁盤(pán)磁頭移動(dòng)的機(jī)制OperatingSystemConceptsStorageHierarchy

分級(jí)的存儲(chǔ)系統(tǒng)Storagesystemsorganizedinhierarchy.存儲(chǔ)系統(tǒng)根據(jù)以下因素組織成分級(jí)體系：Speed速度Cost成本Volatility非易失（永久存儲(chǔ)）Caching–copyinginformationintofasterstoragesystem;mainmemorycanbeviewedasalastcacheforsecondarystorage.高速緩存－將信息拷貝到快速的存儲(chǔ)系統(tǒng)。主存可以二級(jí)存儲(chǔ)器的上一級(jí)的高速緩沖。OperatingSystemConceptsStorage-DeviceHierarchy

分級(jí)存儲(chǔ)設(shè)備OperatingSystemConceptsCaching

緩沖Useofhigh-speedmemorytoholdrecently-accesseddata.用高速主存保存最近訪問(wèn)的數(shù)據(jù)。Requiresacachemanagementpolicy.要求高速緩沖的策略。Cachingintroducesanotherlevelinstoragehierarchy.Thisrequiresdatathatissimultaneouslystoredinmorethanoneleveltobeconsistent.OperatingSystemConceptsMigrationofAFromDisktoRegister

將A從磁盤(pán)遷移到寄存器OperatingSystemConceptsHardwareProtection

硬件保護(hù)Dual-ModeOperation雙模式操作I/OProtectionI/O保護(hù)MemoryProtection存儲(chǔ)保護(hù)CPUProtectionCPU保護(hù)OperatingSystemConceptsDual-ModeOperation

雙模式操作Sharingsystemresourcesrequiresoperatingsystemtoensurethatanincorrectprogramcannotcauseotherprogramstoexecuteincorrectly.Providehardwaresupporttodifferentiatebetweenatleasttwomodesofoperations.1. Usermode–executiondoneonbehalfofauser.2. Monitormode(alsokernelmodeorsystemmode)–executiondoneonbehalfofoperatingsystem.OperatingSystemConceptsDual-ModeOperation(Cont.)

雙模式操作(續(xù))Modebitaddedtocomputerhardwaretoindicatethecurrentmode:monitor(0)oruser(1).Whenaninterruptorfaultoccurshardwareswitchestomonitormode.特權(quán)指令只有在管態(tài)或核心模式下才能執(zhí)行。

monitoruser中斷或異常設(shè)置用戶模式OperatingSystemConceptsI/OProtection

I/O保護(hù)AllI/Oinstructionsareprivilegedinstructions.所有的I/O指令都是特權(quán)指令。Mustensurethatauserprogramcouldnevergaincontrolofthecomputerinmonitormode(I.e.,auserprogramthat,aspartofitsexecution,storesanewaddressintheinterruptvector).必須確保用戶程序不能獲得核心模式（即用戶程序不能將中斷向量表修改成用戶程序的地址）OperatingSystemConceptsUseofASystemCalltoPerformI/O

使用系統(tǒng)調(diào)用執(zhí)行I/O操作OperatingSystemConceptsMemoryProtection

內(nèi)存保護(hù)Mustprovidememoryprotectionatleastfortheinterruptvectorandtheinterruptserviceroutines.至少要為中斷向量表和中斷服務(wù)程序提供存儲(chǔ)保護(hù)。Inordertohavememoryprotection,addtworegistersthatdeterminetherangeoflegaladdressesaprogrammayaccess:為了提供存儲(chǔ)保護(hù)，使用以下兩個(gè)寄存器決定程序可以訪問(wèn)的合法的地址Baseregister–holdsthesmallestlegalphysicalmemoryaddress.基址寄存器－保存最小的合法的物理內(nèi)存的地址Limitregister–containsthesizeoftherange界限寄存器－表示合法地址的范圍Memoryoutsidethedefinedrangeisprotected.存儲(chǔ)器超出定義的范圍就受到保護(hù)。OperatingSystemConceptsUseofABaseandLimitRegister

使用基址寄存器和界限寄存器OperatingSystemConceptsHardwareAddressProtection

硬件地址保護(hù)OperatingSystemConceptsHardwareProtection

硬件保護(hù)Whenexecutinginmonitormode,theoperatingsystemhasunrestrictedaccesstobothmonitoranduser’smemory.當(dāng)操作系統(tǒng)在管態(tài)下執(zhí)行時(shí)，系統(tǒng)和用戶的存儲(chǔ)空間都有沒(méi)有限制的訪問(wèn)權(quán)限。Theloadinstructionsforthebaseandlimitregistersareprivilegedi