A Software-hardware Collaborating Framework for Wear Leveling on Phase Change Memory

DRAM has been used as main memory in most systems, but its scalability and energy consumption are difficult to improve because of its architecture nature. Phase change memory (PCM) is a new non-volatile memory, which addresses these problems and is a promising candidate to replace DRAM as main memory. Since PCM cell has a very limited lifetime, many hardware methods have been proposed to improve its endurance with only low-level information about physical memory operations. Meanwhile, operating system manages physical page mapping, and it has the knowledge of memory layout as well as memory requirements of each process. This paper investigates write behaviors of different memory areas of processes, and proposes a software-hardware collaborating framework that captures process write behavior with simple hardware to enable process write behavior predication by operating system. The framework combines operating system and PCM controller that exploits write behaviors of processes to aid in PCM wear leveling. The results show this framework helps reduce PCM page swaps for wear leveling by 63% on average. And it also lowers the writes of the most worn page by 12% with single process, and by 21% with two parallel processes sharing the PCM.