By analyzing preemptions in embedded real-time systems adopting RM scheduling policy

created a preemption model of periodic real-time tasks. This model described the relationship between overheads incurred by preemptions and the properties of real-time tasks

such as priorities

periods

execution times

deadlines

release times etc. It also showed the relation between the schedulability of the task set and properties of its real-time tasks. Based on the model and taking the idea of parasitism in biology

this paper presented a method of optimizing real-time performance of the embedded systems under the RM scheduling mechanism. This method can reduce preemptions or change the relations of preemptions

decrease overheads to improve real-time performance by adjusting release times of tasks. And then the optimization method underlying the model is evaluated by experiments.