Opportunistic Migration for Hybrid Memories While Mitigating Aging Effects

Hybrid memory systems composed of Non-volatile memory (NVM) and DRAM to exploit the high density of NVM and low access latency of DRAM. Phase Change Memory (PCM), a type of non-volatile memory, is a viable choice for main memory. High write latency and high voltage requirements for PCM lead to Biased Temperature Instability (BTI) aging and performance degradation. De-stressing the memory circuit at regular intervals controls BTI aging. Memory performance can be enhanced by migrating the highest write count memory pages across memory units. Migration and de-stress halt the service of regular requests and affect the performance of the system. Therefore, it is crucial to control migration and de-stress to enhance hybrid memory performance while mitigating BTI aging. We propose DOPMig, a de-stress-aware page migration technique. The policy migrates write-intensive pages to DRAM at regular intervals but opportunistically parallel to the de-stress operation. This method of background migration helps to reduce the migration overheads and improves performance. DOPMig achieves a performance gain of 22%, and improves memory service rate by 15%, and increases DRAM access by 24%.