Systems and methods for coherence in clustered cache hierarchies

Abstract

According to embodiments described herein, the hierarchical complexity for coherence protocols associated with clustered cache architectures can be encapsulated in a simple function, i.e., that of determining when a data block is shared entirely within a cluster (i.e., a sub-tree of the hierarchy) and is private from the outside. This allows embodiments to eliminate complex recursive coherence operations that span the hierarchy and instead employ simple coherence mechanisms such as self-invalidation and write-through but which are restricted to operate where a data block is shared. Thus embodiments recognize that, in the context of clustered cache hierarchies, data can be shared entirely within one cluster but can be private (unshared) to this cluster when viewed from the perspective of other clusters. This characteristic of the data can be determined and then used to locally simplify coherence protocols.