計(jì)算機(jī)操作系統(tǒng)

Computeroperatingsystem

Thefirstchapter

Thegoalandfunctionofthecomputeroperatingsystem

1.1.1goals:

1.Thevalidity

(1)improvesystemresourceutilization

(2)increasethethroughputofthesystem

2.Theconvenience

3.Thescalability

4.Open

Theactionofthe1.1.2operatingsystem

Theinterfacebetweentheuserandthecomputerhardwaresystem

Theusercanusethecomputerinthefollowingways:

(1)commandmode

(2)thesystemcallmode

(3)graphics,windowmode

Asamanagerofcomputersystemsresources

Realizetheabstractionofresources

1.1.3drivesthedevelopmentoftheoperatingsystem

Increasetheutilizationofcomputerresources

2.Theconvenienceofcustomers

Theconstantupdatingofthedevice

Thedevelopmentofcomputerarchitecture

Thedevelopmentoftheoperatingsystem

1.2.1nooperatingsystemcomputersystem

Manualoperation

Disadvantages:

(1)theuserownsthewholemachine

(2)theCPUwaitsformanualoperation

Offlineinput/output

Advantages:

(1)theCPUidletimeisreduced

(2)increasesI/Ospeed

1.2.2singlebatchprocessingsystem

Singlebatchprocessingsystemprocess

Singlebatchprocessingsystemcharacteristics

(1)theautomaticity

(2)sequential

(3)singlechannel

1.2.3multiplebatchprocessingsystems

Thebasicconceptofmultiprogramming

Inthesystem,thetasksthatuserssubmitarestoredinaqueue,

whichiscalleda"standbyqueue”.Thejobdispatcherthen

selectsseveraljobsintomemoryfromthebackupqueuebya

certainalgorithm,allowingthemtosharethevariousresources

intheCPUandsystem.

Benefitsofmulti-programmingtechniques:

(1)increaseCPUutilization

(2)increasetheutilizationofmemoryandI/Odevices

(3)increasesystemthroughput

Theprosandconsofmultiplebatchprocessingsystems:

(1)resourceutilizationishigh

(2)systemthroughputislarge

(3)theaverageturnaroundtimeislong

(4)nointeractioncapability

Multiplebatchprocessingsystemsneedtobeaddressed

(1)themanagementoftheprocessor

(2)memorymanagementissues

I/Oequipmentmanagementproblem

(4)filemanagementissues

(5)problemofoperationmanagement

1.2.4time-sharingsystem

Create:meettheuser'srequirements:

(1)man-machineinteraction

(2)theSharedhost

(3)itiseasyforuserstogetonthemachine

Definition:aconnectiononahostmultipleterminalwitha

monitorandkeyboard,andallowsmultipleuserstothrough

theirownterminals,interactivelyusingthecomputer,the

resourcesSharedhosting.

Criticalissuesintheimplementationofthetime-sharing

system

Thekeyquestionishowdousersinteractwiththeirjobs

(1)receivingintime

(2)timelytreatment

Thejobgoesdirectlyintomemory

3.Features:

(1)multiple

(2)independence

(3)thetimeliness

interaction

1.2.5realtimesystem

Definition:thesystemcanrespondtotherequestofthe

externalevents,withintheprescribedtimetocompletethe

handlingoftheaffair,coordinatedoperationandcontrolof

allreal-timetasks.

1.Theapplicationrequirements

(1)real-timecontrol

(2)real-timeinformationprocessing

2.Thereal-timetasks

1)theexecutionofataskisdividedbyperiodicity

(1)periodicreal-timetasks

(2)non-periodicreal-timetasks

Note:thereisastartingdeadlineorcompletiondeadline

2)bedividedaccordingtothedeadline

(1)hardwork

(2)softtasks

Thecomparisonofreal-timesystemwithtime-sharingsystem

characteristics

(1)multiplexing.Thereal-timesystemismainlyperformedby

thesystem'speriodicsamplingofmulti-channelfield

informationandthecontrolofmultipleobjectsormultiple

actuators.Themultiplexingofthetime-sharingsystemhasto

dowiththeuser，ssituation,whentherearetoofew.

(2)independence.

(3)timeliness.Thereal-timesystemresponsetimeistypically

millisecondsorlessthan100microseconds.

(4)interactivity.

Theinteractionofareal-timesystemislimitedtoaccessto

certainspecializedservicesforthesystem.

(5)reliability.Real-timesystemrequirementssystemwith

highreliability,inreal-timesystems,oftenadopts

multilevelfaulttolerantmeasurestoprotectthesecurityof

systemanddatasecurity.

Thedevelopmentofmicrocomputeroperatingsystem

Singleusersingle-taskoperatingsystem

1)theCP/M

eight

2)ms-dos

16

Singleusermultitaskoperatingsystem

Multi-usermultitaskingoperatingsystem

OnbehalfoftheUNIXOS

1)theSolarisOS

2)LinuxOS

Thebasicfeaturesoftheoperatingsystem

1.3.1concurrency

Parallelandconcurrency

Parallelismistheoccurrenceoftwoormoreeventsatthesame

time,whileconcurrencyreferstotwoormoreeventsoccurring

atthesametimeinterval.Ifthereismorethanoneprocessor

inacomputersystem,thesecanconcurrentexecutionofthe

programcanbeassignedtomultipleprocessingmachine,realize

theparallelexecution,namelyeachprocessorisusedtodeal

withaprogramthatcanexecuteconcurrently,inthisway,more

programswillbeexecutedatthesametime.

2.Theintroductionoftheprocess

Aprocessisabasicunitthatcanrunindependentlyofthe

systemandbeallocatedasaresource.

3.Theintroductionofthethread

InanOSthatintroducesthreads,theprocessistypicallythe

basicunitofallocatingresources,andthethreadasthebasic

unitofindependentrunningandindependentscheduling

1.3.2sharing

Sharingreferstotheresourcesavailableinthesystemtobe

usedjointlybyprocesses(threads)thatcanbeexecuted

concurrentlyinmemory,collectivelyusingresourcesas

resourcesharing.

Howtoshareresources:

Mutuallyexclusivesharing

OnlyaftertheAprocesshascompletedandreleasedtheresource,

anotherprocessisallowedtoaccesstheresource.

Accessthesameway

Concurrencyandsharingaretwoofthemostbasic

characteristicsoftheoperatingsystem,andtheyareeach

other,sconditions.

1.3.3virtualtechnology

Virtualreferstoatechniquethatturnsaphysicalentityinto

anumberoflogicalcounterpoints.

Therearetwowaystoimplementvirtualtechnologiesinthe

operatingsystem:

Time-divisionreusetechniques

Alsocalledtime-sharingtechnology,aphysicalchannelis

virtualasmultiplelogicalchannels.

1)virtualprocessortechnology

Tosetupaprocessforeachprogram,letmultipleprograms

executeconcurrently,usingaprocessorinordertodivide

time.

2)virtualappliancetechnology

AphysicalI/OdeviceisvirtualtomultiplelogicalI/Odevices

andallowseachusertotakeupalogicalI/Odevice

Spacereusetechnology

1)virtualdisktechnology

2)virtualmemorytechnology

Usethefreetimeofmemorytostoreotherprogramstoimprove

memoryutilization.

1.3.4asynchrony

Theprocessmovesforwardatanunpredictablespeed,whichis

theasynchronousnatureoftheprocess.

Themainfunctionofthe1.4operatingsystem

1.4.1processormanagementfunctions

Createandcancellationprocess(thread),totheoperationsof

theprocess(threads)tocoordinatetheexchangeofinformation

betweenprocesses(thread),anddistributingtheprocessorto

processaccordingtocertainalgorithm(thread).

1.Processcontrol

Createaprocessforthejob,revokethecompletedprocess,and

controlthestatetransitionsintherunningprocess.Inthe

presentOS,processcontrolshouldalsohavethecapabilityto

createseveralthreadsforaprocessandtoundothethreadthat

hascompletedthetask.

2.Processsynchronization

Themaintaskistocoordinatetheoperationsofmultiple

processes(includingthreads),andtherearetwotypesof

coordination:

(1)processmutualexclusion.

Whenaccessingcriticalresources,themutexshouldbeused.

(2)processsynchronization.

Thismeansthattheprocesses(threads)thatworktogetherto

completeacommontaskarecoordinatedbythesynchronization

organization.

3.Theprocessofcommunication

Theexchangeofinformationbetweenmutuallycooperative

processes(threads).

4.Thescheduling

Everyjobwaitingonthebackupqueueneedstobescheduledto

execute.Inatraditionaloperatingsystem,twostepsinclude

jobschedulingandprocessscheduling.

(1)jobscheduling.

Selectafewjobsfromthebackupqueue,allocatememoryfor

them,andthencreateaprocessthatinsertsthemintotheready

queuebyacertainalgorithm.

(2)processscheduling

Selectaprocessfromthereadyqueueoftheprocess,assign

theprocessortoit,andsetuptheruntimetomaketheprocess

execute.

1.4.2memorymanagementfunctions

Therunningofmulti-channelprogramsprovidesagood

environmentforuserstousememory,improvememoryutilization,

andextendmemorylogically.Todothis,youshouldhavethe

followingfunctions:

1.Thememoryallocation

Allocatememoryspaceforeachprogram;Improvedmemory

utilizationtoreduceunusedmemoryspace;Allowsapplications

thatarerunningtoapplyforadditionalmemoryspace.

IntheOS,therearetwokindsofdistributionmode,thestatic

anddynamic,staticallyallocatedmemoryspaceisfixedandnot

"move”,dynamic,otherwise,youmayapplyforadditionalmemory

space.

Implementingmemoryallocationrequiresthefollowing

structureandfunctionmemoryallocationmechanism:

(1)memoryallocationdatastructures.Recordmemoryusage.

(2)memoryallocation.Thesystemallocatesmemoryfortheuser

bycertainalgorithm.

(3)memoryrecal1function.

2.Memoryprotection

Toensurethateachuserprogramcanonlyrunintheirownmemory

space(settwo1imitregister,theupperboundandlowerbound

onthehardwareconditions,stillneedsoftwares),independent

ofeachother;Neverallowuserstoaccesstheoperating

system，sprogramsanddata;Nordoesitallowuserstomoveto

othernon-shareduserprograms.

3.Addressmapping

Theaddressspaceintheprogram,calledthe"logicaladdress”,

startswith'0".Theaddressspaceinmemoryiscalledaddress

space,whichiscalled''physicaladdress”.Anaddressmapping

isaphysicaladdressthattransformstheaddressspaceinto

amemoryspace.Hardwaresupportisrequired.

4.Memoryexpansion

Usingvirtualstoragetechnologytoaugmentmemoryfromlogic,

thesystemmusthaveamemoryextensionmechanismwiththese

features:

(1)requestformediation.

(2)replacingfunction.

Devicemanagementfunction

Tomanageallperipheralsinthecomputersystem,thefollowing

functionsshouldbeincluded:

1.Thebuffermanagement

2.Equipmentdistribution

3.Theequipmentprocessing

1.4.4filemanagementfunctions

Manageuserfilesandsystemfilestoensurethesafetyof

documents.

Managethefilestoragespace

Thefilesystemmanagesthestoragespaceofmanyfilesand

files.Themaintaskistoallocatethenecessaryexternal

storagespaceforeachfile,improvetheutilizationofthe

externalstorage,andhelptoimprovethestorageandspeedof

thesystem.

2.Thedirectorymanagement

Themaintaskistosetupthedirectoryentryforeachfile

andtoorganizealargenumberofcatalogitemsforconvenient

accesstothename.

Read/writemanagementandprotectionofdocuments

(1)reading/writingmanagementofdocuments

(2)fileprotection

Preventunapproveduseraccessfiles

Topreventimpostoraccessfiles

Preventtheuseoffilesinanincorrectmanner

Theinterfacebetweentheoperatingsystemandtheuser

Convenienceusersusetheoperatingsystem.Interfacescanbe

dividedinto:

(1)theuserinterface.Theinterfaceprovidedtotheuser.

(2)programinterface.

1.Theuserinterface

Youcancontrolyourownworkdirectlyorindirectly,andthe

operatingsystemprovidesacommandinterfacetotheuser.

(1)theonlineuserinterface

Asetofkeyboardcommandsandcommandinterpretersforonline

users

(2)offlineuserinterface

Asetofhomeworkcontrollanguage(JCL),whichisusedfor

batchjobusers

(3)thegraphicaluserinterface

Adoptgraphicalinterface

2.Theprograminterface

Theonlywayausercangetanoperatingsystemservice.

Consistsofasetofsystemcalls

1.5OSdesign

Nostructuredoperatingsystem(thefirstoperatingsystem)

Modularoperatingsystem(secondgenerationoperatingsystem)

1)basicconceptsofmodularprogrammingtechniques

Designeachmodulehassomeaspectfunction

Theindependenceofthemodule

Highcohesionandlowcoupling

3)theadvantagesofmoduleinterfaces

(1)improvingthecorrectness,intelligibilityand

maintainabilityofOSdesign;

(2)enhancingtheresilienceoftheOS;

(3)acceleratingthedevelopmentoftheOS

Thereisaproblem

(1)theinterfacerequirementsaredifficulttomeettheactual

requirementsoftheinterfaceafterthemoduleiscomplete

(2)disorder

LayeredstructureOS(thirdgenerationoperatingsystem)

Theconceptofalayeredstructure

Thelayerislaidupfromthebottomupandseveralfunctions

areimplementedineachlayer

2)theadvantagesanddisadvantagesofthelayeredstructure

advantages

(1)thecorrectnessofthesystem

Eachlayerisbuiltonamorereliablebasis

(2)easytoexpandandmaintainability

Adding,modifying,orreplacingahierarchyofmodulesor

entirelayers,withoutchangingthecorrespondinginterface,

willnotaffectotherlevels.

Disadvantages:thesystemislessefficient

MicrokernelstructureOS(fourth-generationOS)

Customer/servermode(C/Spattern)

Systemcomposition:client,server,andnetworksystem

Theinteractionbetweentheclient/server

(1)thecustomersendsarequestmessage

(2)theserverreceivesthemessage

(3)theserversendsthemessageback

(4)theclientreceivesthemessage

Advantagesofthecustomer/servermodel

(1)thedistributionprocessingandstorageofdata

(2)itiseasytocentralizemanagement

(3)flexibilityandextensibility

(4)easytoadaptapplicationsoftware

1.5.3object-orientedprogramming

Thebasicconceptofobject-orientedtechnology

Object:abstractofaseriesofthingsthathavethesame

propertiesandobeythesamerules,concreteobjectsare

instancesofobjects.Intheobjectorientedtechnology,isthe

useoftheencapsulateddatastructure(variables)andaset

ofoperatingprocess(method)ofit,torepresentanobjectin

thesystem.

Theobjectclassdefinesobjectsthatarebroadlysimilar.

3)inheritance

Bydefininganewclassbyanexistingclass,thesubclass

automaticallyinheritsthevariablesandmethodsdefinedinthe

parentclassandallowsthesubclasstobesubclassed

Addnewcontent.Allowsasubclasstohavetwoparentclasses

ormultipleparentclasses,whichcanrangefrommultiple

Aparentisinherited,whichiscalled"multipleinheritance”.

Thebenefitsofobject-orientedtechnology

(1)improveproductqualityandproductivitythrough“reuse”

(2)makethesystemmoreflexibleandscalable

(3)itiseasiertoensurethe"correctness"and"reliability”

ofthesystem

The1.5.4microkernelOSstructure

Thebasicconceptofthe2.1process

Thesequentialexecutionofthe2.1.1programandits

characteristics

Thesequentialexecutionoftheprogram

Toanapplicationisdividedintoseveralproceduressection,

betweenvariousproceduressection,andwillbeimplementedin

acertainorderorder,onlythecurrentoperationafterthe

(application),canperformsubsequentoperations.

Thecharacteristicsofthesequentialexecutionoftheprogram

(1)sequentiality:theoperationoftheprocessorisstrictly

executedintheorderspecifiedbytheprogram,thatis,each

operationmustbeginafterthelastoperation.

(2)seal:procedureisperformedinaclosedenvironment,

namelywholemachineresourcesofprogramexecution,thestate

oftheresources(inadditiontotheinitialstate)onlythis

procedurecanchangeit.Oncetheprogramisexecuted,its

executionresultsareunaffectedbyexternalfactors.

(3)thereproducibility:aslongastheprogramexecutionwhen

theenvironmentisthesameastheinitialconditions,whenthe

programisexecutedrepeatedly,constantlyperformedfrom

beginningtoend,or“stop-go"toperform,willgetthesame

result.

2.1.2diagram

1.Theformerisfigure(PrecedenceGraph):nocyclicGraph

isaDirected,writtenforDAG(DirectedAcyclicGraph),used

todescribetheprocessbetweenexecutioncontext.

(1)thePartialOrderRelation,PartialOrder):alsocalled

predecessorrelationships(Precedencebase)"-Pi->Pj,

whichiscalledPiisthedirectprecursortoPj,Pjisthe

directsuccessortoPi.

(2)theInitialNode(InitialNode):theNodewithoutthe

previousdrive.

(3)terminatingtheNode(FinalNode):nosubsequentnodes.

Weight(Weight):theexecutiontimeofthenumberofprograms

ornodesthatthenodecontains.

2.1.

Concurrentexecutionoftheprogramanditscharacteristics

Concurrentexecutionoftheprogram

Thecharacteristicsofconcurrentexecutionofprograms

1)theintermittent

2)lossofclosure

Noreproducibility

Thecharacteristicsandstatesofthe2.1.4process

Inordertoenabletheprogramtoexecuteconcurrently,andto

describeandcontroltheprogramsthatexecuteconcurrently,

introducethe“process”.

Thecharacteristicsofaprocess

1)structuralfeatures

Theprogramsegment,theassociateddatasegment,andthe

ProcessControlBlockProcessControlBlockconstitutethe

Processentity,alsocalledtheProcessimage.The

establishmentprocessoftenreferstothePCBthatestablishes

theprocess,andtheundoprocessreferstothePCBthat

retractedtheprocess.

2)dynamic

Themostbasicfeatureofaprocess

3)concurrency

Theimportantcharacteristicsofaprocess,processentities

canexecuteconcurrentlywithotherprocessentities,andthe

program(withoutPCB)cannotbeexecutedconcurrently.

4)independence

Aprocessentityisabasicunitthatcanrunindependently,

distributeresourcesindependently,andaccepttheschedule

independently.NoprogramthatdoesnotestablishPCBwillbe

abletooperateasanindependentunit.

5)asynchrony

Referstotheprocessofmovingforwardinanindependent,

unpredictablespeed,ortheprocessentityisrunning

asynchronously.

Theprocessisdefinedinseveralways:

The(1)processisanexecutionoftheprogram.

(2)aprocessisaprogramanditsdatathatperformsthe

activitiesthatoccurinsequenceexecutionofthemachine.

Aprocessisaprocessthatrunsonadatasetofaprogramthat

isanindependentunitofsystemresourceallocationand

scheduling.

Afterintroducingconceptofprocessentities,canputthe

processinthetraditionalOSdefinedas:"theprocessisthe

realoperationprocessoftheprocess,isthesystemofresource

allocationandschedulingofaseparateunit”.

Thethreebasicstatesoftheprocess

Therunningprocessmayhavethreebasicstates:

(1)theReadystate

Whentheprocesshasbeenallocatedtoallthenecessary-

resourcesotherthantheCPU,itcanbeexecutedimmediately

assoonastheCPUisobtained,andthestateoftheprocess

iscalledthereadystate.

(2)executionstatus

TheprocesshasreceivedtheCPUanditsprogramisexecuting.

Inasingle-processorsystem,onlyoneprocessisinexecution;

Inmultiprocessorsystems,multipleprocessesarein

execution.

(3)blockingstate

Theprocessbeingexecuted,whichistemporarilyunableto

continueexecutionduetoanevent,issuspendedfromthe

processorandiscalledblockingstate.

3.Pendingstate

1)thereasonfortheintroductionofasuspendedstate

(1)theenduser,srequest

(2)theparentprocessrequest

(3)theneedforloadregulation

(4)operatingsystemrequirements

Thetransformationoftheprocessstate

Suspendedstate(orstaticstate)andatransitiontoa

non-suspendedstate(alsocalledactivestate):

(1)theactivityisready->standsstill

TheactivityreadystateisexpressedasReadya,andwhenthe

SuspendissuspendedfromtheSuspend,theprocessisconverted

toastaticreadystateforReadys.

(2)theactivityblocks->standsstill

TheactiveblockingstateBlockeda,suspendtheblockingstate

Blockeds.

(3)thestationarystate->activityisready

IntheReadysstateprocess,theprocesswillchangetoBlockeda

stateifActiveactivationoftheActiveprimitiveis

activated.

(4)staticblocking->isblocked

Createastateandterminatestate

1)createastateof

ProcesseshavetheirownPCBatthistime,buttheprocess

itselfhasnotyetenteredthemainmemory,whichcreatework

isnotdone,theprocessalsocan，tbescheduledtorun,its

stateistocreate.

2)terminationstatus

The2.1.5processcontrolblock

Thefunctionofprocesscontrolblock

TodescribeandControltheProcessofrunning,thesystem

definesadatastructureforeachProcess,ProcessControl

BlockPCB(ProcessControlBlock),itispartoftheProcess

entities,isthemostimportantintheoperatingsystemof

recordingdatastructure.PCBistheonlysignofaprocess.

Theprocesscontrolstheinformationinthemodule

Processidentifier

Touniquelyidentifyaprocess.Aprocessusuallyhastwo

identifiers:

(1)aninternalidentifier

Auniquedigitalidentifierforaprocess,usuallyasequence

numberofaprocess,isconvenientforthesystemtouse.

(2)externalidentifiers

Itisprovidedbythecreator,usuallyaletter,anumber,and

isoftenusedwhentheuser(process)isaccessingtheprocess.

2)processorstate

Theprocessorstateinformationisprimarilycomposedofthe

contentsofthevariousregistersoftheprocessor.Al1this

informationmustbekeptinPCBwhentheprocessoris

interrupted.Theseregistersinclude:ageneralpurpose

register

Instructioncounter

Theprogramstatusword,PSW

Theuserstackpointer

3)processschedulinginformation

(1)processstatus

Processprioritystatus

Otherinformationrequiredforprocessdispatch

(4)events

4)processcontrolinformation

Addressofprogramanddata

Processsynchronizationandcommunicationmechanisms

(3)resourcelist

(4)linkpointer

Organizationofprocesscontrolblocks

DuetothenumberofPCBinthesystem,thePCBshouldbe

organizedinana