Integrated application and operating system optimization

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The primary objective of this research project is to allow applications to realize the performance potential of emerging computer hardware systems, by dynamically optimizing execution paths across multiple software layers. The main challenge in achieving this objective arises from the growing complexity of computer systems and the many layers of abstraction that have been developed to help manage this complexity. Twotechnology trends highlight the problem.  First, emerging micro-processors (such as Sun's multi-core, multithreaded Niagara) have subtle performance characteristics that are extremely difficult to understand and exploit, even for expert programmers. At the same time, programmers are using languages such as Java, where the code is interpreted by an abstract machine.  The productivity gains that these languages provide are based, in part, on a higher-level abstraction that frees the programmer from the unpleasant details of real hardware. Between the code written by programmers and the instructions executed by the real hardware lie many other layers, including a language-level virtual machine, the operating system, a low-level virtual machine, and a virtual machine monitor. This scenario is quite likely to arise in current web hosting centres.     Our research explores a variety of ways to break down at run-time the barriers imposed by static layers of abstraction. As one specific project, we will explore integrating compiler-based memory management algorithms into a Java JIT compiler, so that the generated code can interact with the JVM's heap management system, which will in turn inform the operating system of candidates for page prefetch and replacement. As a second specific project, we will investigate the use of dynamically-generated execution traces within the operating system code itself (past projects have applied these techniques to user-level code only). Our initial goal will be to support enhanced profiling and performance instrumentation of the OS, followed by dynamically optimizing execution paths within the OS, with the ultimate goal of integrating user-level and system-level execution traces.