Coherence as an Abstract Type

We are currently designing Sparks, a protocol construction library that we hope will allow us to improve the performance of DSM systems to within a few percent of tightly-coupled multiprocessors. Sparks' abstractions will allow us to cleanly and systematically explore the design space of highlevel synchronization operations, rather than proposing and implementing new operations in an ad hoc fashion. Sparks' basic abstraction is the coherence history, an object that summarizes past coherence actions to shared segments. Our emphasis here is more on creating and investigating the abstractions that make a broad variety of optimizations possible, rather than on the individual optimizations themselves. However, we will thoroughly quantify the performance gains allowed by the synchronization types created via the Sparks library. Our overall goal is to improve DSM performance. We will gauge our success by targeting applications from benchmark suites such as SPLASH-2, as well as representative applications from computational chemistry, biology, and satellite image analysis. Sparks' history abstraction will be used to make several important contributions towards our performance goal: (1) efficient techniques to implement high-level synchronization, (2) efficient automatic prefetching using prefetch playbacks, and (3) external interfaces to run-time libraries and automatically paralle lized code sections. By improving DSM efficiency, we hope to make the shared memory paradigm more appealing, and therefore useful, to the research community