Increasing TLB reach with multiple pages size subblocks

While superpages are an efficient solution to increase TLB reach, strong requirements for using superpages hinder an actual utilization. Subblock TLBs release some of these requirements and thus increase the actual utilization of superpages by attaching afield per subblock (or base page) in a superpage. On the other hand, its superpage size is strongly restricted because the number of attached fields should be the same with the superpage size in base page unit. We propose VS-TLBs (Variable-size Subblock TLB), which extend subblock TLBs to allow a subblock to be multiple base pages, while the subblock size in subblock TLBs is a base page. Therefore, with the same number of the attached fields, the TLB reach of VS-TLBs becomes much larger than subblock TLBs. By virtue of the increased TLB reach, the number of TLB misses are reduced considerably. We propose two system configurations: VS-TLB alone and VS-hybrid. VS-hybrid replaces the subblock TLB with VS-TLB in the hybrid scheme of the subblock TLB and the shadow memory. The simulation results show that the two proposed configurations reduce 52% and 67% of TLB misses from the results of their parent systems.