STATE-BASED ALLOCATION AND REPLACEMENT FOR IMPROVED HIT RATIO IN DIRECTORY CACHES

摘要

A system and method of maintaining consistent cached copies of memory in a multi-node processor system having a distributed shared main memory (250), includes a memory directory (210) having entries (240) mapping the main memory, an access history information (420) in the memory directory entries, and a directory cache (200) having records (350) corresponding to a subset of the memory directory entries. The method includes the steps of receiving a signal indicating a processor cache miss, retrieving from the memory directory a memory directory entry corresponding to the miss, updating the access history of the memory directory entry and only if the updated access history indicates that copies are cached in two or more modes, selecting a directory cache line (320) for eviction based on its access history and allocating the retrieved memory directory entry to the directory cache in place of the evicted line.