中科大操作系统原理与实现课件5_CPU_Scheduling0.pdf
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中科大操作系统原理与实现课件5_CPU_Scheduling0.pdf

中科大操作系统原理与实现课件5_CPU_Scheduling0.pdf

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操作系统原理与设计第5章CPUScheduling(1)陈香兰中国科学技术大学计算机学院2009年09月01日......CPUschedulingisthebasisofmultiprogrammedOSes.......提纲——.CPUscheduling(1)BasicConceptsCPU-I/OBurstCycleCPUSchedulerPreemptiveSchedulingDispatcherSchedulingCriteriaSchedulingCriteriaSchedulingAlgorithmsFCFSSchedulingSJFSchedulingPrioritySchedulingRoundRobinSchedulingMultilevelQueueSchedulingMultilevelFeedbackQueueScheduling.小结和作业......ObjectiveofmultiprogrammingIMaximumCPUutilization......Outline.BasicConceptsCPU-I/OBurstCycleCPUSchedulerPreemptiveSchedulingDispatcherSchedulingCriteriaSchedulingCriteriaSchedulingAlgorithmsFCFSSchedulingSJFSchedulingPrioritySchedulingRoundRobinSchedulingMultilevelQueueSchedulingMultilevelFeedbackQueueScheduling.小结和作业......CPU-I/OBurstCycleIIApropertyofprocess:CPU-I/OBurstCycleIProcessexecutionconsistsofacycleofCPUexecutionandI/OwaitIProcessexecution=n(CPUexecution+I/Owait)IAlternatingSequenceofCPUAndI/OBursts......CPU-I/OBurstCycleIIICPUburstdistributionIHistogramofCPU-burstTimes......Outline.BasicConceptsCPU-I/OBurstCycleCPUSchedulerPreemptiveSchedulingDispatcherSchedulingCriteriaSchedulingCriteriaSchedulingAlgorithmsFCFSSchedulingSJFSchedulingPrioritySchedulingRoundRobinSchedulingMultilevelQueueSchedulingMultilevelFeedbackQueueScheduling.小结和作业......CPUSchedulerICPUscheduler(Short-termScheduler)ISelectsfromamongtheprocessesinmemorythatarereadytoexecute,andallocatestheCPUtooneofthemIReadyQueue:IFIFOQueue?Ibypriority?Itree?Iunorderedlinkedlist?......Outline.BasicConceptsCPU-I/OBurstCycleCPUSchedulerPreemptiveSchedulingDispatcherSchedulingCriteriaSchedulingCriteriaSchedulingAlgorithmsFCFSSchedulingSJFSchedulingPrioritySchedulingRoundRobinSchedulingMultilevelQueueSchedulingMultilevelFeedbackQueueScheduling.小结和作业......PreemptiveSchedulingIICPUschedulingdecisionsmaytakeplacewhenaprocess:1.Switchesfromrunningtowaitingstate2.Switchesfromrun