Proactively Invalidating Dead Blocks to Enable Fast Writes in STT-MRAM Caches

Spin-Transfer Torque Magnetic Random Access Memory (STT-MRAM) is a promising emerging memory technology for on-chip caches. It has a low read access time and low leakage power. Unfortunately, however, STT-MRAM suffers from its long write latency and high write energy consumption. This paper proposes a cache management technique called Proactive Invalidation (PROI) that proactively invalidates dead blocks in advance to enable fast writes in the STT-MRAM caches. Experimental evaluation shows that the proposed technique improves performance by 14% on average compared to the baseline STT-MRAM cache. This paper also proposes two optimization techniques called Proactive Invalidation-aware Data Encoding (PIDE) and Narrowness-aware Partial Write (NPW) to minimize the energy overheads of Proactive Invalidation. Experimental results demonstrate that the total energy consumption of the STT-MRAM cache with PROI is only 1.8% higher than the baseline when PROI is applied with PIDE and NPW.