QoS adaptation in real -time systems.

Abstract

We propose to design, implement, and evaluate a software framework, called the <italic>Adaptware</italic>, that consists of architectural support, resource-management mechanisms, and programming abstractions for adapting Quality-of-Service (QoS) to dynamically-fluctuating resource capacity and demands. This framework is to reduce the cost and time of real-time software development by providing the infrastructure necessary for building <italic>reusable</italic> multi-purpose real-time software components. In much the same way as today's consumers can buy software and hardware components from different vendors and construct a computing environment tailored to their needs, the proposed framework will provide the means of building and integrating real-time system components so as to preserve their temporal correctness while making it possible to dynamically compute predictable end-to-end temporal guarantees commensurate with available resources. The benefits of our framework are demonstrated by building a testbed and executing representative applications, drawn from both soft real-time systems such as multimedia, and hard real-time systems such as automated flight and process control. Software development costs of these applications will be reduced significantly by separating real-time application design from resource-capacity assumptions on the target platform, hence facilitating changes in platform capacity, configuration or load. We also demonstrate how our abstraction of platform capacity (away from the programmer) can help build real-time systems that can tolerate a range of violations of their load and failure hypotheses by adapting application QoS dynamically to the resources available.