CATCH: A mechanism for dynamically detecting Cache-Content-Duplication and its application to instruction caches

Abstract

Cache-Content-Duplication (CCD) occurs when there is a miss for a block in a cache and the entire content of the missed block is already in the cache in a block with a different tag. Caches aware of content-duplication can have lower miss rates by allowing only blocks with unique content to enter a cache. This work examines the potential of CCD for instruction caches. We show that CCD is a frequent phenomenon and that an idealized duplication-detection mechanism for instruction caches has the potential to increase performance of an out-of-order processor, with a 2-way eight instruction per block 16KB instruction cache, often by more than 5% and up to 20%. This work also proposes CATCH, a hardware based mechanism for dynamically detecting CCD. Experimental results for an out-of-order processor show that a CATCH with a 2.32KB cost usually captures 60% or more of the CCD's idealized potential. © 2008 EDAA.