摘要
通过对采用抢占式EDF算法的嵌入式系统中各实时任务抢占行为的分析 ,建立了一个周期性任务集的抢占模型 ,从数学上描述了抢占关系、可调度性、调度开销与实时任务的周期、执行时间、最终期限、启动时间等属性之间的关系 .依据该抢占模型 ,提出了一个改进的抢占式EDF调度算法 ,通过将基于遗传算法的优化方法离线计算得到的实时任务启动时间作为目标系统的一个调度参数 ,减少抢占次数 ,改变抢占关系 ,从而提高系统的可调度能力和实时性能 .最后用实验验证了改进的抢占式EDF调度算法的有效性 .
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.
出处
《电子学报》
EI
CAS
CSCD
北大核心
2004年第1期64-68,共5页
Acta Electronica Sinica
基金
国家自然科学基金 (No .698730 0 7)
关键词
抢占式EDF
启动时间
抢占模型
实时性能
嵌入式系统
Genetic algorithms
Mathematical models
Optimization
Personal computers
Real time systems
Scheduling
