Stability of Adaptive Distributed Real-TimeSystems with Dynamic Resource Management
Sergiu Rafiliu · Linköping University Electronic Press eBooks · 2013
T oday's embedded distributed real-time systems, are exposed to large variations in resource usage due to complex software applications, sophisticated hardware platforms, and the impact of their run-time environment.As efficiency becomes more important, the applications running on these systems are extended with on-line resource managers whose job is to adapt the system in the face of such variations.Distributed systems are often heterogeneous, meaning that the hardware platform consists of computing nodes with different performance, operating systems, and scheduling policies, linked through one or more networks using different protocols.In this thesis we explore whether resource managers used in such distributed embedded systems are stable, meaning that the system's resource usage is controlled under all possible run-time scenarios.Stability implies a bounded worst-case behavior of the system and can be linked with classic real-time systems' properties such as bounded response times for the software applications.In the case of distributed systems, the stability problem is particularly hard because software applications distributed over the different resources generate complex, cyclic dependencies between the resources, that need to be taken into account.In this thesis we develop a detailed mathematical model of an adaptive, distributed real-time system and we derive conditions that, if satisfied, guarantee its stability.vii viii T here are many people who have contributed, in a way or another, to the development of this thesis.First I would like to thank my thesis advisers prof.Petru Eleş and prof.Zebo Peng for the time that they have invested into my education, the inspiring and sometimes energetic meetings, and the encouragement and support that they have offered during my years as a PhD student.I would also like to thank prof.Michael Lemmon and the members of his research group at the University of Notre Dame (USA), Department of Electrical Engineering, for the insightful discussion we had during my time there.Many thanks go to my colleagues at the Department of Computer and Information Science (IDA) for the excellent working environment, especially to Eva Pelayo Danils, Gunilla Mellheden, and Anne Moe for making the