摘要:把具有不同重要性的功能集成到一个共享平台上的混合关键级系统，是当前嵌入式系统发展的主要趋势之一.已有的混合关键级调度理论为了保证高关键级作业的完成，大多不支持关键级向下切换，在系统进入高关键级后直接放弃低关键级作业的执行，这对系统中作业集的整体完成率有负面影响.为了应对这一问题，把需求边界分析理论扩展到混合关键级作业系统中，提出了作业的动态需求边界函数，以矢量的形式记录系统在运行时需求边界函数的动态变化，并相应地提出了作业的混合关键级松弛时间与系统关键级松弛时间的概念.在此基础上，提出了一种基于动态需求边界的混合关键级作业调度算法CSDDB （criticality switch based on dynamical demand boundary）.该算法选择具有最小松弛时间的关键级作为执行关键级，在保证高关键级作业可调度的情况下，充分利用系统资源，尽可能地满足低关键级作业的执行.应用随机生成的任务集进行仿真实验，结果表明，与已有算法相比，CSDDB在系统关键级的保证与作业集整体完成率方面比现有算法有10%以上的提升.



Abstract:An important trend in embedded system is integrating functions with different level of importance into a sharing hardware platform, which is called mixed-criticality system. Most of the existing mixed-criticality theory did not support switching the system criticality from high to low in order to guarantee the jobs with higher criticality, which is not good for the overall performance of the system. To deal with this problem, this paper expands the traditional demand boundary analysis theory to the mixed-criticality systems, presenting the concept of dynamical demand boundary for mixed-criticality jobs, which represents the dynamical demand of jobs in run-time as a vector. And then, based on the concept of slack time for mixed-criticality jobs and the criticality of system, the paper presents an algorithm CSDDB (criticality switch based on dynamical demand boundary). The algorithm chooses the criticality with the minimum slack time as the execution criticality of the system to take full advantage of system resources and to guarantee the execution of jobs with lower criticality without affecting the schedulability of high criticality jobs. Experiments with randomly generated workload show that CSDDB makes more than 10% of progress in guaranteeing the system criticality and the completion of jobs set compared with the existing research.



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