LastingNVCache: A Technique for Improving the Lifetime of Non-volatile Caches

Use of non-volatile memory (NVM) devices such as resistive RAM (ReRAM) and spin transfer torque RAM (STT-RAM) for designing on-chip caches holds the promise of providing a high-density, low-leakage alternative to SRAM. However, low write endurance of NVMs, along with the write-variation introduced by existing cache management schemes significantly limits the lifetime of NVM caches. We present LastingNVCache, a technique for improving the cache lifetime by mitigating the intra-set write variation. LastingNVCache works on the key idea that by periodically flushing a frequently-written data-item, next time the block can be made to load into a cold block in the set. Through this, the future writes to that data-item can be redirected from a hot block to a cold block, which leads to improvement in the cache lifetime. Microarchitectural simulations have shown that LastingNVCache provides 6.36X, 9.79X, and 10.94X improvement in lifetime for single, dual and quad-core systems, respectively. Also, its implementation overhead is small and it outperforms a recently proposed technique for improving lifetime of NVM caches.