lecture_4_process description and control

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1、ProcessDescriptionandControlZhaoFangOperatingSystems-forthecollagestudentsGoalsforTodayWhatisaProcess?ProcessStatesProcessDatastructuresProcessControlExecutionoftheOperatingSystemUNIXSVR4ProcessManagementRequirementsofanOSInterleavetheexecutionofsevera

2、lprocessestomaximizeprocessorutilizationwhileprovidingreasonableresponsetimeAllocateresourcestoprocessesSupportinterprocesscommunicationandusercreationofprocesses3ManageExecutionofApplicationsResourcesmadeavailabletomultipleapplicationsProcessorisswitched

3、amongmultipleapplicationTheprocessorandI/Odevicescanbeusedefficiently4ProcessAprograminexecutionAninstanceofaprogramrunningonacomputerTheentitythatcanbeassignedtoandexecutedonaprocessorAunitofactivitycharacterizedbytheexecutionofasequenceofinstructions,a

4、currentstate,andanassociatedsetofsysteminstructions5ProcessCompositionAprocessiscomprisedof:Programcode(possiblyshared)AsetofdataAnumberofattributesdescribingthestateoftheprocessProcessElementsIdentifierStatePriorityProgramcounterMemorypointersConte

5、xtdataI/OstatusinformationAccountinginformation7ProcessControlBlockContainstheprocesselementsCreatedandmanagebytheoperatingsystemAllowssupportformultipleprocesses8TraceoftheProcessThebehaviorofanindividualprocessisshownbylistingthesequenceofinstructions

6、thatareexecutedThislistiscalledaTraceDispatcherisasmallprogramwhichswitchestheprocessorfromoneprocesstoanotherProcessExecutionConsiderthreeprocessesbeingexecutedAllareinmemory(plusthedispatcher)Letsignorevirtualmemoryforthis.TracefromtheprocessespointsE

7、achprocessrunstocompletionTracefromProcessorspointsTimeoutI/OTracefromProcessorspointswecandrawatimelineofCPUactivity,identifyingthestatesoftheprocessesandDispatcherExampleExecution14Two-StateProcessModelProcessmaybeinoneoftwostatesRunningNot-runningQueui

8、ngDiagramEtc…processesmovedbythedispatcheroftheOStotheCPUthenbacktothequeueuntilthetaskiscompetedProcessBirthandDeathCreationTerminationNewbatchjobNormalCompletionInteractiveLoginMemoryun