US Patent 7437520 Adaptive snoop-and-forward mechanisms for multiprocessor systems

In a network-based cache-coherent multiprocessor system, when a node receives a cache request, the node can perform an intra-node cache snoop operation and forward the cache request to a subsequent node in the network. A snoop-and-forward prediction mechanism can be used to predict whether lazy forwarding or eager forwarding is used in processing the incoming cache request. With lazy forwarding, the node cannot forward the cache request to the subsequent node until the corresponding intra-node cache snoop operation is completed. With eager forwarding, the node can forward the cache request to the subsequent node immediately, before the corresponding intra-node cache snoop operation is completed. Furthermore, the snoop-and-forward prediction mechanism can be enhanced seamlessly with an appropriate snoop filter to avoid unnecessary intra-node cache snoop operations.