On the Use and Performance of Explicit Communication Primitives in Cache-coherent Multiprocessor Systems

Recent developments in shared-memory multiprocessor systems advocate using off-the-shelf hardware to provide basic communication mechanisms and using software to implement cache coherence policies. The exposure of communication mechanisms to software opens many opportunities for enhancing application performance. In this paper we propose a set of communication primitives that are absent from pure cache coherent schemes. The communication primitives, implemented on a communication co-processor, introduce a flavor of message passing and permit protocol optimization, without sacrificing the simplicity of the shared memory systems. To assess the overhead of the software implementation of the primitives and protocols, we compare, via simulation, the execution of three programs from the SPLASH-2 suite on four environments: a PRAM model, a hardware cache coherence scheme, a software scheme implementing only the basic cache coherence protocol, and an optimized software solution supporting the ..