Architectural and Implementation Tradeoffs in the Design of Multiple-Context Processors

We examine two multiple-context schemes in the context of scalable shared-memory multiprocessors. The blocked scheme switches between contexts at cache misses. The proposed interleaved scheme switches between available contexts on a cycle-by-cycle basis, while providing full pipeline interlocks for good single-context performance. We show the interleaved scheme to have a performance advantage over the blocked scheme due to its ability to hide pipeline dependencies and reduce the context switch cost. We also show that, while the implementation of the interleaved scheme is more complex, this complexity is not overwhelming.