Limits on speculative module-level parallelism in imperative and object-oriented programs on CMP platforms

We consider program modules, e.g. procedures, functions, and methods as the basic method to exploit speculative parallelism in existing codes. We analyze how much inherent and exploitable parallelism exists in a set of C and Java programs on a set of chip-multiprocessor architecture models, and identify what inherent program features, as well as architectural deficiencies, that limit the speedup. Our data complement previous limit studies by indicating that the programming style-object-oriented versus imperative-does not seem to have any noticeable impact on the achievable speedup. Further, we show that as few as eight processors are enough to exploit all of the inherent parallelism. However, memory-level data dependence resolution and thread management mechanisms of recent CMP proposals may impose overheads that severely limit the speedup obtained.