政企大客户营销技巧培训

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1、ModernOperatingSystemsChapter2–Process&ThreadZhangYangSpring20132.1Processes2.2ThreadsContentofthislecture2.1Processes2.2ThreadsModernWorkstationsandPCsMultiplewindowsinpersonalcomputerdoingcompletelyindependentthingsWord,Excel,Photoshop,E-mail,music,etc

2、.MultipleactivitieswithinoneapplicationE.g.,inMicrosoftWordReadingandinterpretingkeystrokesFormattinglineandpagebreaksDisplayingwhatyoutypedSpellcheckingHyphenation….WhenthereisasingleprogramrunningintheCPU,itleadstothedegradationoftheCPUutilization.Exam

3、ple:WhenarunningprograminitiatesanI/Ooperation,theCPUremainidleuntiltheI/Ooperationiscompleted.SolutiontothisproblemisprovidedbyMultiprogramming.Multiprogramming(1)DefinitionAmodeofoperationthatprovidesfortheinterleavedexecutionoftwoormoreprogramsbyasing

4、leprocessor.ImprovingCPUutilizationByallowingseveralprogramstoresideinmainmemoryatthe“sametime”theCPUmightbeshared,suchthatwhenoneprograminitiatesanI/Ooperation,anotherprogramcanbeassignedtotheCPU,thustheimprovementoftheCPUutilization.Multiprogramming(2)

5、AllowsmultipleapplicationstorunatthesametimeExampleInsequentialenvironment,Aexecutesfirst,thenB.Concurrency(1)Example(ctd.)ConcurrencyConcurrency(2)ABCPUDEV1DEV1CPU10152025CPUDEV2CPU3035DEV24045CPUDEV2BenefitsofConcurrencyWhatarethelimitationswithoutconc

6、urrency?LongresponsetimeResourcesunderutilizedBetterresourceutilizationResourcesunusedbyoneapplicationcanbeusedbytheothersBetteraverageresponsetimeNoneedtowaitforotherapplicationstocompleteIssuesrelatedtoconcurrencyItiseasiertodoonethingatatime.Problemsw

7、ithdoingmultiplethings:ApplicationsneedtobeprotectedfromoneanotherAdditionalcoordinationmechanismsamongapplicationsOverheadtoswitchamongapplicationsPotentialperformancedegradationwhenrunningtoomanyapplicationsUsers,Programs,ProcessesUsershaveaccountsonth

8、esystemUserslaunchprogramsManyusersmaylaunchsameprogramOneusermaylaunchmanyinstancesofthesameprogramTheprocessisanOSabstractionforarunningprogramProcess:anexecutingprogramProcessesareinstancesofaprogramThe“program”canreall