Low Overhead Dynamic QoS Optimization under Variable Task Execution Times

Today´s embedded systems are typically exposed to varying load, due to e.g. changing number of tasks and variable task execution times. At the same time, many of the most frequent real-life applications are not characterized by hard real-time constraints and their design goal is not to satisfy certain hard deadlines in the worst case. Moreover, from the user´s perspective, achieving a high level of processor utilization is also not a primary goal. What the user needs, is to exploit the available resources (in our case processor time) such that a high level of quality of service (QoS) is delivered. In this paper we propose efficient run-time approaches, able to distribute the processor bandwidth such that the global QoS produced by a set of applications is maximized, in the context in which the processor demand from individual tasks is continuously varying. Extensive experiments demonstrate the efficiency of the proposed approaches.