The WISCONSIN MULTIFACET PROJECT is performing research to improve multiprocessor servers for commercial workloads. Relative to scientific workloads, we find commercial applications use fewer processors and suffer many more sharing misses that must be satisfied by other processors. Both aspects suggest that extending snooping cache coherence might be more attractive than switching to directory protocols.
This talk will discuss two complementary proposals for mitigating the twin concerns regarding snooping. First, MULTICAST SNOOPING [ISCA '99] reduces snooping's bandwidth requirements by using selective multicasts rather than always broadcasting. Second, TIMESTAMP SNOOPING [ASPLOS '00] allows designers to implement snooping on any interconnect topology by implicitly attaching logical timestamps to coherence transactions. The presentation will spend more time on the newer timestamp snooping proposal. C.f. http://www.cs.wisc.edu/multifacet/.