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.