Synonymous address compaction for energy reduction in data TLB

Abstract

Modern processors can issue and execute multiple instructions per cycle, often performing multiple memory operations simultaneously. To reduce stalls due to resource conflicts, most processors employ multi-ported L1 caches and TLBs to enable concurrent memory accesses. In this paper, the authors observed that data TLB lookups within a cycle and across consecutive cycles are often synonymous - they go to the same page. To exploit this finding, two new mechanisms were proposed - intra-cycle compaction and inter-cycle compaction of address translation requests in order to save energy in the data TLB. The results showed that average energy savings of 27% using intra-cycle, 42% using inter-cycle in a conventional d-TLB, and 56% using inter-cycle compaction in semantic-aware d-TLBs can be achieved. When these 2 compaction techniques are combined together and applied to both the i-TLB and semantic-aware d-TLBs, an average energy savings of 76% (up to 87%) is obtained.