Finite Ready Queues As a Mean for Overload Reduction in Weakly-Hard Real-Time Systems

Abstract : Finite ready queues, implemented by buuers, are a system reality in embedded real-time computing systems and networks. The dimen-sioning of queues is subject to constraints in industrial practice, and often the queue capacity is suucient for typical system behavior but is not suucient in peak overload conditions. This may lead to overrow and consequently to the discarding of jobs. In this paper, we explore whether nite queue capacity can also be used as a mean of design in order to reduce workload peaks and thus shorten a transient overload phase. We present an analysis method which is to the best of our knowledge the rst one able to give (a) worst-case response times guarantees as well as (b) weakly-hard guarantees for tasks which are executed on a computing system with nite queues. Experimental results show that nite queue capacity may only a have weak overload limiting eeect. This unexpected outcome can be explained by the system behavior in the worst-case corner cases. The analysis shows nevertheless that a trade-oo between weakly-hard guarantees and queue sizes is possible.