Adaptive Memory and Storage Fusion on Non-Volatile One-Memory System

Non-volatile memory (NVM), such as phase change memory (PCM), can be a promising candidate to replace DRAM because of its lower leakage power and higher density. Since PCM is non-volatile, it can also be used as storage to support in-place execution and reduce loading time. However, as conventional operating systems have different strategies to satisfy various constraints on memory and storage subsystems, using PCM as both memory and storage in a system requires thorough consideration on the system's inherent constraints, such as limited lifetime, retention time requirements, and possible overheads. Most existing work still divide NVM into separated memory and storage parts, but this strategy still incurs the overhead of loading data from storage to memory as in conventional systems. In our work, we rethink the data retention time requirements for PCM memory/storage and develop an adaptive memory-storage management strategy to dynamically reconfigure the One-Memory System, with considerations of the current average write-cycle and the number of retention-Time qualified frames for storage, to reduce the extra data movement between memory and storage with a limited lifetime sacrifice. Experimental results show that our adaptive design improves the performance by reducing 86.1% of the extra writes of data movement, and only 3.4% of the system's lifetime is sacrificed.