回卷恢复模型下容错实时系统的可调度性分析

Schedulability Analysis for Fault-tolerant Real-time System Under Rollback Recovery Model

实时任务的超时完成将会导致灾难性后果,因此实时系统必须具备严格的实时性及可靠性保障.考虑实时系统的容错需求,本文基于回卷恢复模型,对容错实时系统的可调度性分析进行研究.在基于任务最坏响应时间的可调度性分析方法中,容错优先级配置是决定系统可调度性的关键.为了改进系统的可调度性,提出一种容错优先级可降低的配置策略,并推导出此策略下任务最坏响应时间的计算公式,以判断系统的可调度性.降低策略下低优先级任务可挪用高优先级任务的空闲时间来满足自身的截止时限要求.仿真实验表明,降低任务的容错优先级可以有效提升系统的容错能力.

A real-time system is required to guarantee its stringent requirements in real-time response and reliability since any task fail- ing to response correctly witahin its deadline may result in a catastrophe. Based on the rollback recovery model, the paper presents a schedulability analysis for fault-tolerant real-time systems taking account of the effects of errors. The schedulability analytical method based on worst-case response time is applied in which fault-tolerant priority configuration is crucial to the system＇s schedulability. The main contribution of the approach is to deduce the computing formula of task~ worst-case response time under a new priority configu- ring strategy which allows the lower priority task using the higher priority tasks spare time to meet its deadline by lowering the faulty tasks priority levels. The simulation shows that decreasing tasks fault-tolerant priority can improve system fault resilience efficiently.