Hardware prediction of OS run-length for fine-grained resource customization

In the past ten years, computer architecture has seen a paradigm shift from emphasizing single thread performance to energy efficient, throughput oriented, chip multiprocessors. Several studies have suggested that it may be worthwhile to off-load execution of the operating system (OS) to one or more of these cores, or reconfigure hardware during OS execution. To be effective, these techniques must balance the cost of off-loading or re-configuration, versus the potential benefits, which are typically unknown at decision time. These decision points are typically implemented by manually instrumenting a few OS routines (out of hundreds). Such a preliminary research effort cannot be sustained across several operating systems and hardware configurations. We argue that decisions made in software are often sub-optimal because they are expensive in terms of run-time overhead and because applications vary in their use of OS features. We propose that these decision mechanisms should be supported through a hardware based OS run-length predictor, that removes the onus from OS developers. Our final design results in a 95% prediction accuracy for OS intensive applications, while requiring only 2 KB of storage.