Data Locality Exploitation in Cache Compression

State-of-the-art cache compression methods compress multiple neighboring blocks often called as a sector into a single 64-byte block to effectively enlarge the cache capacity. A compressed block is created by storing 4-byte data patterns as dictionary entries and pointers to them for compressing multiple blocks. Furthermore, sector-based tag array maintains one-to-one mapping between tag and data arrays in order to preserve conventional cache access mechanism. We present a dual-block compression method which uses an entire uncompressed block as dictionary and compresses multiple neighboring blocks in a separate companion block to provide a larger dictionary for better compression ratios. Furthermore, we introduce the concept of buddy-set which expands the compressible candidate blocks across two adjacent cache sets to enlarge the scope of compression. Performance evaluations for the last-level cache show that the proposed dual-block compression with expansion of compressible candidates in the buddy-set can enlarge the cache by an average of 60% while current state-of-art compression proposal has only 29% improvement. The proposed scheme demonstrates 8.9% speedup over caches without compression.