Q-Fabric: System Support for Continuous Online Quality Management
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The explosive growth in networked systems and applications and the increase in device capabilities (as evidenced by the availability of inexpensive multimedia devices) enable novel complex distributed applications, including video conferencing, on-demand computing services, and virtual environments. These applications' need for high performance, real-time, or reliability requires the provision of Quality of Service (QoS) guarantees along the path of information exchange between two or more communicating systems. Execution environments that are prone to dynamic variability and uncertainty make QoS provision a challenging task, e.g., changes in user behavior, resource requirements, resource availabilities, or system failures are difficult or even impossible to predict. Further, with the coexistence of multiple adaptation techniques and resource management mechanisms, it becomes increasingly important to provide an integrated or cooperative approach to distributed QoS management. This work's goals are the provision of system-level tools needed for the efficient integration of multiple adaptation approaches available at different layers of a system (e.g., application-level, operating system, or network) and the use of these tools such that distributed QoS management is performed efficiently with predictable results. These goals are addressed constructively and experimentally with the Q-Fabric architecture, which provides the required system-level mechanisms to efficiently integrate multiple adaptation techniques. The foundation of this integration is the event-based communication implemented by it, realizing a loosely-coupled group communication approach frequently found in multi-peer applications. Experimental evaluations are performed in the context of a mobile multimedia application, where the focus is directed toward efficient energy consumption on battery-operated devices. Here, integration is particularly important to prevent multiple energy management techniques found on modern mobile devices to negate the energy savings of each other.