A Fault-Tolerant L1 Cache with Predictable Performance by Virtual Filter Cache

The Subblock-Disabling schemes have obviousadvantages on delays overhead and capacity loss. However, theexistence of cache line "holes" triggers abundant false hits andthe utilization of available cache capacity is low. A subblockdisablingbased no-collision set-level mending cache architectureVFCcache suited for low set-associative L1 cache is proposed. AnAdditional Tag Array is added and VFCcache is logically dividedinto two parts, MainCache and Virtual Filter Cache (VFC). Theno-collision set-level mending mechanism maybe causes thedivergence of practical associativity and faulty sets. VFC canmask these faulty sets, alleviate such divergence and make theperformance predictable. According to the experiments in Simics, the performance has an increase of 11.73% compared to theBuddy Cache for a 32KB 4-way L1 cache with a failureprobability of 0.004. The average miss rate of the L1-D has adecrease of 5.20% and that of the L1-I has a decrease of 5.02%for 29 benchmarks from SPEC CPU2000/2006 in comparisonwith Buddy Cache.