QoS scheduling components based on firm real-time requirements

Summary form only given. In the last years, multimedia and feedback control applications have emphasized the importance of appropriate resource allocation policies in real-time systems, introducing the problem of controlling and adapting the quality of service (QoS) provided by an application. The basic idea is then to avoid overload situations by scaling down the applications resource requirements, while sustaining a specified QoS level for the system. In this paper, we are interested in the problem of dynamic QoS driven CPU allocation for hybrid sets of tasks, consisting of firm periodic tasks, i.e, tasks allowing occasional skips of instances) and soft aperiodic requests. The approach seeks to establish a compromise between minimizing the response time of aperiodic requests and maximizing the QoS of periodic tasks. First, we briefly present the library of free software components developed within the French National project CLEOPATRE (work supported by the French research office, grant number 01K0742). Then, we focus on the functioning of the QoS management component. Finally, we present some simulation results to underline the interest of such a scheduling scheme for real-time applications´ developers.