Application Awareness in Adaptation Middleware: Balancing Transparency with Performance and Adaptivity. Dimitrios S. Nikolopoulos and Andreas Stathopoulos. Abstract: The complexity of today's microprocessors and parallel environments prohibits most applications from achieving even a small percentage of their performance. The situation is exacerbated on modern multi-user, heterogeneous, highly variable environments such as Computational Grids. Unfortunately, this complexity cannot be hidden efficiently in the operating system. A host of middleware is developed for this purpose, and often application-level resource management is necessary. System-aware applications and application-aware systems should perform runtime optimizations to capture most of the available performance in the desired metric. This talk addresses such runtime optimizations at all three interoperating levels, operating system, middleware, applications.