Patent ID: 8244983

Claim:
A memory control system, comprising: a master directory associated with memory and comprising master directory entries to store information regarding copies of memory lines stored in a plurality of memory caches; a directory cache to cache directory information of at least some of the master directory entries in the master directory such that the directory information of the at least some of the master directory entries is present in both the directory cache and the master directory, wherein the directory cache has a plurality of directory cache entries to store the directory information of the at least some master directory entries, and wherein each directory cache entry comprises one or more bits configured to store an ownership state that indicates whether a corresponding master directory entry lacks a memory cache owner; and a memory controller configured to free for re-use ones of the directory cache entries by, accessing a particular directory cache entry; determining whether the ownership state of the particular directory cache entry indicates that a corresponding master directory entry lacks a memory cache owner, and if so, then i) skipping a master directory update process wherein directory information stored in the particular directory cache entry is written to the master directory, and ii) claiming for re-use the particular directory cache entry, wherein, if the ownership state of the particular directory cache entry fails to indicate that the corresponding master directory entry lacks a memory cache owner, then the memory controller is configured to i) initiate the master directory update process wherein directory information stored in the particular directory cache entry is written to the master directory, and ii) claim for re-use the particular directory cache entry.