An optimized multicore cache coherence design for exploiting communication locality

Supporting cache coherence in current multicore processor still faces scalability and performance problems. This paper presents an optimized cache coherence design targeting at NoC-based multicore processors. It tries to achieve the best characteristics both of the snooping and of the directory-based protocols. With the observation of network traffic locality, we design a cache coherence that aims at local and remote access separately. At the first level, snooping is achieved within a cache group and at the second level of the protocol, the coarse directories provide the caches with information about which processors must be involved in first level snooping. To support efficient coherence broadcasting, we also propose a low latency, broadcast-enabled underlying NoC design. It incorporates light weight buses into NoCs, where the snooping protocol can be performed in a broadcast fashion. Extensive experimental results demonstrate that the proposed coherence design can achieve low complexity and high performance goals.