操作系统作业4姓名,学号.docx

操作系统作业4姓名,学号.docx

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橾作系统课柱作业

操作系统作业4

姓名，学号

1.Why istheseparationofmechanismandpolicydesirable?

Answer:

Mechanismandpolicymustbeseparatetoensurethatsystemsareeasytomodify.Notwosysteminstallationsarethesame,soeachinstallationmaywanttotunetheoperatingsystemtosuititsneeds.Withmechanismandpolicyseparate,thepolicymaybechangedatwillwhilethemechanismstaysunchanged.Thisarrangementprovidesamoreflexiblesystem.

2.·whatarethetwomodelsofinterprocesscommunication?

Whatarethestrengthsandweaknessesofthetwoapproaches?

Answer:

Thehvomodelsofintetprocesscommunicationaremessage-passingmodelandtheshared-memorymodel.Messagepassingisusefttlforexchangingsmalleramountsof

da,tabecausenoconflictsne,edbeavoided.Itisalsoeasiertoimplementthanisshared

memoryforintercomputercommunication.Sharedn1emoryallowsmaximumspeedandconvenienceofcommunication,sinceitcanbedoneatmemorytransferspeedswhenittakesplacewithinacomputer.However,thismethodcompromisesonprotectionandsynchronizationbel\veentheprocessessharingmemory

3.Includingtheinitialparentprocess,bowmanyprocessesarecreatedbytheprogramshowninFigurel?

#include#include

int main（）

｛

int i;

for （i一O;i<4;i++）

fork（）;

｝

returnO;

Figure1:

ProgramforQuestion3.

2

Answer:

16processesarecreated.

Hint:

YoumayincludeprintfOstatementstobetterunderstandbowmanyprocesseshavebeencreated.

4..Explainthecircumstancesunderwhichthelineofcodemarkedprintf（"LINEJ"）inFigure2willbereached

#include#include#include

int main（）

｛

pid_t pid;

I*forkachildprocess*Ipid=fork（）;

if （pid

｝

elseif （pid==0） { I*childprocess*I

execlp（"/bin/ls","ls",NULL）;printf（"LINEJ"）;

｝

else{/*parentprocess*I

I*parentwillw吐t for the childtocomplete*I

w吐t（NULL）;

｝

printf（"ChildComplete"）;

｝

returnO;

Fi驴re2:

ProgramforQuestion4.

橾作系统课柱作业

3

Answer:

ThecalltoexecOreplacestheaddressspaceoftheprocesswiththeprogramspecifiedastheparametertoexecQ.IfthecalltoexecOsucceeds,thenewprogramisnowrunningandcontrolfromthecalltoexec（）neverreturns.ltithisscenario,thelineprintf（"LineJ"）;wouldneverbeperformed.However,ifanerroroccmsinthecalltoexecO,thefunctionren1rnscontrolandthereforthelineprintf（"LineJ"）;wouldbeperformed.

5.UsingtheprograminFigure3,identifythevaluesofpidat1inesA,B,C,andD.（Assumethattheactualpidsoftheparentandchildare2600and2603,respectively.）

#includes

#include#include

intmain{）

｛

picLtpid,pidl;

I*forkachildprocess寒／pid frok（）;

if （pid<0）{/•erroroccurred•/fprintf（stderr,"ForkFaile心）；return1;

｝

elseif（pidsc 0）{/•childprocess•/pidl•getpid（）;

printf（"child:

pid=¼d",pid）;/亭A*Iprintf（"child:

pid1=¼d",p过1）;/•B•I

｝

else{/•parentprocess•/pidl=getpid（）;

｝

printf（"parent:

pid=i.d",pid）;/拿C拿／printf（"parent:

p工di•i.d",pidl）;/*D•I11ait（NULL）;

｝

returnO;

Figure3:

ProgramforQuestion5.

Answer:

A=0,B=2603,C=260,3D=2600

4

橾作系统课柱作业

6.UsingtheprogramshowninFigure4,explainwhattheoutputwillbeat

linesXandY.

#include<芍s/types.h>#include#include

#defineSIZE5

int nums[SIZE]={0,1,2,3,4};

int main（）

｛

inti;

pid_t pid;

pid=fork（）;

if （pid=0）{

for （i=O;i

nums［i] •=-i;

printf（"CHILD:

%d11,nums [i]）;/•LINEX•/

｝

｝

elseif （pid>0）{

wait（NULL）;

for （i =O;i

｝

rpintf（"PARENT:

加 ",nums[i]）;I*LINEY•/

｝

returnO;

Figure4:

ProgramforQuestion6.

Answer:

Becausethechildisacopyoftheparent,anychangesthechildmakeswilloccurinitscopyofthedataandwon'tbereflectedintheparent.Asaresult,thevaluesoutputbythechildatlineXare0,-1,-4,-9,-16.ThevaluesoutputbytheparentatlineYare0,I,2,3,4

5

操作系统课杠作业

7.Whichofthefollowingcomponentsofprogramstatearesharedacrossthreadsinamultithreadedprocess?

a.Registervalues

b.Heapmemory

c.Globalvariables

d.Stackmemory

Answer:

Thethreadsofamultithreadedprocessshareheapmemoryandglobalvariables.Eachthreadhasitsseparatesetofregistervaluesandaseparatestack.

8.Asystemwithtwodual-coreprocessorshasfourprocessorsavailableforscheduling.ACPU-intensiveapplicationisrunningonthissystem.Allinputisperformed