Abstract: To enhance the scheduling performance of aperiodic task in Numerical Control(NC)system tasks scheduling,a preallocation-based slack-stealing algorithm was proposed.An off-line pre-allocating sub-algorithm was used to reserve time intervals for periodic tasks,and the idle times of scheduler accessible were advanced as soon as possible by postponing the execution of periodic tasks.At run time,the reserved intervals for periodic tasks were modified to give aperiodic tasks the maximum idle time to execute.The theoretical performance analysis demonstrated that the proposed algorithm could provide the shortest aperiodic response time with much less implementation complexity and memory requirement,while guaranteed the stringent timeliness requirements of period tasks.The effectiveness and optimality of the algorithm were verified by the simulation.

Key words: numerical control system, hybrid scheduling, aperiodic task, pre-allocation

摘要： 为改善数控系统混合任务调度中非周期任务的调度性能,提出一种基于预分配的空闲挪用算法。任务调度开始前,采用预分配子算法为实时周期任务预留处理器时间,通过推迟实时周期任务的执行,使周期任务调度中的空闲时间尽可能提前。任务调度过程中,根据周期任务的执行情况动态调整其预留时间,为非周期任务提供最大的可用空闲时间。算法性能分析及仿真实验表明,所提算法在保证实时周期任务的截止时限要求的同时,能够以较小的计算及存储开销取得最短的非周期任务响应时间。

关键词: 数控系统, 混合调度, 非周期任务, 预分配