Ex3Word文档下载推荐.docx

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d.Whatisathread?

Neweroperatingsystemsprovidethreadswhichallliveinthesameaddressspaceandsharetheirfiledescriptors.Thethreadcanbedefinedasaseparatestreamofexecutionthattakesplacesimultaneouslywithandindependentlyofeverythingelsethatmightbehappening.

e.Whyarethreadsuseful?

Firstly,itspendslesstimetocreateanewthreadthanaprocesswiththereasonthatthenewlycreatedthreadonlyusesthecurrentprocessaddressspace,buttheprocessnot.

Secondly,itisquickertoendathreadthanaprocess.Becausethethreadsoccurinthesamecurrentprocessaddress,soitisquickertoswitchbetweenthreadsthanprocesses.

Thirdly,forthesamereasonmentionedabove,thedatawhichareproducedbyonethreadcanbesharedbyanotherthreadimmediately,alsomuchfasterthanprocesses.

NowletustryusingtheTimestampprogramandruntwothreads.

Right-clickonTimestamp.exeandsaveprogramindriveC.ThisprogramshouldbeexecutedintheWindowscommandconsole.OpentheWindowscommandconsolebyclickingontheStartmenuondesktop,andthenselectRun...Type"

cmd"

inthetextfieldandclickOK.AtthepromptC:

\,type"

Timestamp–i500000–p2>

Output.out"

;

pressENTER.

Note:

-ispecifiesthenumberofworkcycles,and-pspecifiesthenumberofthreadstorun.

Nowusethegraphicalinterfacetoseetheoutput.

Right-clickonGraph.exeandsavetheprograminDriveC.Opentheprogram.IfGraph.exedoesnotrun,refertoAppendixA.RunningaVisualBasicFileforinstructions.OnceGraph.exeisopened,clickSelectDataFile,andchoosethefileOutput.outindriveC.

Notethatthehorizontalaxisisthenumberofworkcycles.Eachthreadisdistinguishedbyadifferentcolor.Thegrayareasindicatethatthesystemisnotrunningthegiventhreads.Alegendforthethreadsisdisplayedatthebottomofthegraph.

f.Captureascreenshotofthegraphicaloutput.

g.Listtheorderinwhichthethreadsarebeingexecuted.

1-1-2-2-1-1-2

h.Whatisacontextswitch?

Howdoyouknowacontextswitchoccurredfromthegraph?

WhenswitchingtheCPUtoanotherprocessrequiressavingthestateoftheoldprocessandloadingthesavedstateforthenewprocess,whichisknownasacontextswitch.Acontextusuallyoccurswhenaninterruptappearsonthescreen.

i.Whatactivitiesareperformedbytheprocessorduringacontextswitch?

AninterruptoccursanditwilldosomethingtomakingnotesoftheaddressofthelastinstructionexecutedandthenswitchCPUtoanotherprocess.

j.Explainwhatishappeningintermsofpreemptivemultitaskingandwhateffectithastotheuser.

Theprocessorcanassigndifferentprioritiestodifferenttypesofinterrupts.Thelow-speeddeviceshavelowpriorityandthehigh-speeddeviceshavehighpriority.Thehighprioritydevicescaninterruptthelowprioritydevicesbutthelowprioritydevicescan’tinterruptthehighprioritydevices.

k.Aninterruptindicatesthatthethreadisnotbeingrunandshouldthereforebefollowedbyagraygap.Howdoesthekernelhandleaninterrupt?

Atfirst,theinputdevicesendstotheprocessoranIRQ.WhentheprocessorreceivesthissignalofIRQ,itstopsexecutingtheapplicationprogram,makingnotesoftheaddressofthelastinstructionexecuted.Then,itswitchestotheaddressoftheinterrupthandy,andstartsexecutingtheinstructionswhereitfinds.

Tryusingmorethantwothreads.

AttheWindowscommandpromptC:

\,type“Timestamp–i500000–p[enterthenumberofthreadstorun（lessthan10）]”andpressENTER.

l.Copyandpastethegraphicaloutput.

m.Listtheorderinwhichthethreadsarebeingexecuted.

1-2-1-1-2-3-4-4-5-5-5-3-4-4-5-6-7-7-8-6-7-8-9

n.Considerasetofthreeprocessesthatareexecutedtocompletion.ProcessAtakes6seconds,ProcessBtakes3seconds,andProcessCtakes5seconds.Abouthowlongwouldittakeforalltheprocessestobecompletedusingpreemptivemultitasking,morethan14seconds,lessthan14seconds,orexactly14seconds?

Explainyouranswer.

Morethan14seconds,becausethecontextswitchesalsocosttimes

Nowinvestigateyourownsystem.

o.HowmuchRAM（mainmemory）doesyourmachinehave?

Showproofofyouranswerbysubmittingascreenshotofthedisplayfromwhichyouinferredyouranswer.

512M

LaunchMicrosoftWordifitisnotalreadylaunched.

p.HowmanythreadsdoesMicrosoftWordlaunch?

（Referto3.1.4Lab:

TheTaskManager.）Showproofofyouranswerbysubmittingascreenshotofthedisplayfromwhichyouinferredyouranswer.

10

q.HowmuchmemorydoesMicrosoftWordconsume?

Showproofofyouranswerbysubmittingascreenshotofthedisplayfromwhichyouinferredyouranswer.

27368KB

Question2.VirtualMemory

Inthissection,youwilluseaprogramdemonstratinghowvirtualmemoryisused.

a.Howdoesvirtualmemoryworkusingapagetable?

Wheninvirtualmemory,everyaddresscanbetranslatedintoaphysicalmemoryaddressbyapagetable.Foreverypageinthevirtualaddressspace,thepagetablegivestherealaddressinRAMwherethepageislocated.

b.Whatistheprimarypurposeofvirtualmemory?

Itcan“add”thestorageofthememorywhichmeanstheprogramcanbelocatedflexibly.

c.Listthreeadvantagesofusingvirtualmemorywhenexecutingaprogram.

Firstly,theaddressspacetheprocessesassigncanactuallybe“larger”thanthephysicalmemoryavailable.

Secondly,inasystemthatusesvirtualmemory,everyprogramrunsinitsownprivateaddressspace.

Thirdly,usingthevirtualmemoryscheme,asmallamountofRAMisrequiredforaprogramtorun,andtherestoftheprogramsaddressspaceiskeptonthedisk

ExecutethePageReplacementSimulationprogram.

ClickonPaging.exetoruntheapplication.RefertoAppendixA.RunningaVisualBasicFileifPaging.exedoesnotrun.

Noticethetopoftheprogramwindowindicatesthenumberofrequestandtotalpagefaults.ThetableontheleftrepresentsRAMandtheoneontherightrepresentstheharddisk.Theorderofrequestsissetatdefault.Youcanalsoenteryourownorderofrequests.Tochangethespeedofthesimulation,youcanusethespeedadjusteratthebottom-leftoftheprogramwindow.EachtimeyouclickonStoporPause,thesimulationendsafteronecompletememoryaccess.

Starttheprogramusingthedefaultqueueofrequests.

d.Describewhatishappeningforthefirstsevenrequestsstep-by-stepforthedefaultorderofrequests.

Therearefivepagefaults,whichmeansfourrequestsisinvirtualmemory.Atfirst,thecomputerstaketherequesttoRAMandthensendittoCPU.

e.Whendoesapagefaultoccur,andhowdoesthekernelhandleapagefault?

TheaddresstranslationcircuitrychecksthepagetablebutfindsthepageisnotinRAM,soitstartsapagefault（aninterrupt）.Thentheprocessorstopsexecutingtheuserprogramandswitchthecontroltothekernel.Thekernellooksatcertainstatusregisterstomakeclearthatwherethepagefaultcamefromandknowtheprocesswantsaccesstoitsvirtualpage,soitwillgiveRAMandloadinthepagefortheprogram.Afterthatitwillfixupdatethepagetable.Afterawhile,controlwillbereturnedtotheuserprogram.

f.Enterasequenceofeightrequestsinplaceofthedefaultorderofrequestsintheprogramthatwouldcausefourpagefaults.

1,2,3,4,1,2,3,4

g.Inwhatcaseisitundesirabletousevirtualmemory?

Thespeedmaybecomeverylow.

h.Givenatotalpagingfilesizeof267MB,andaRAMofsize256MB.Yourapplicationsarecurrentlytakingup500MBofmemory.Howwouldyourunanapplicationthatconsumes100MBofmemory?

Wecanexpandthevirtualmemory.

Question3.Troubleshooting

Belowarevariousproblemscenarios.Selectthemostlikelycause（s）fortheproblemfromtheCauseslist.

Causes

A.Componentnotpluggedin

B.Applicationsoftwareerror

C.Operatingsystemerror

D.LowRAM

E.Slowprocessor

F.CMOSbatteryfailure

G.Motherboardfailure

H.Harddiskfailure

I.BIOSROMfailure

J.Appropriatecomponentdrivernotinstalledproperly

Problems

a.Programnotresponding

Causes:

D.LowRAMorE.Slowprocessor

b.Screenfrozeaftersuccessfullybooting

C.Operatingsystemerror

c.Programsrunningslowly

d.Peripheraldevicenotworking（mouse,keyboard,printer）

A.ComponentnotpluggedinorJ.Appropriatecomponentdrivernotinstalledproperly

e.Allnecessarycomputersystemcomponentsarepluggedin,butthesystemdoesnotboot

F.CMOSbatteryfailureorG.MotherboardfailureorI.BIOSROMfailure.

f.Thecomputerisbeingbooted,andanerrormessageindicatesthattheharddrivecannotbefound.

H.Harddiskfailure

g.Iflowmemoryisacauseofthesystemrunningslowly,whatcanyoudoasausertospeedupthesystem?

Expandingthestorageofthemainmemoryandthevirtualmemory,whichIthinkisthemostimportant.

Question4.FileDirectories

Inthisquestion,youaregivenazipfile,whichcontainssomefoldersandfiles.Youwillunzipthegivenfile,manipulatethefilesandfolders