Research on Preemptions of Preemptive EDF and Improvement on Its Performance
Zhao Hai · Dianzi xuebao · 2004
By analyzing preemptions of real-time tasks in embedded systems under preemptive EDF (Earliest Deadline First) schedule algorithm,we create a preemption model of periodic real-time tasks.This model describes relationship between overhead occurred by preemptions and the properties of real-time tasks,such as priorities,periods,execution times,deadlines,release times etc.It also shows the relationships among task's properties,preemption orders,schedule overheads and schedulibility.Underlying the model,this paper presents an improved preemptive EDF algorithm,which uses the release times as schedule criteria got by an optimization algorithm.The optimization algorithm is based on genetic algorithm and runs off-line on desktop computers.Using the algorithm can reduce the number of preemptions,change order of preemption,so that the schedule capacity and real-time performance of embedded systems are improved.And then the improved schedule algorithm underlying the model is evaluated by experiments.