Curling-PCM: Application-specific wear leveling for phase change memory based embedded systems

Phase change memory (PCM) has been used as NOR flash replacement in embedded systems with its attractive features. However, the endurance of PCM keeps drifting down and greatly limits its adoption in embedded systems. As most embedded systems are application-oriented, we can better utilize PCM by exploring application-specific features such as fixed access patterns and update frequencies to prolong the lifetime of PCM. In this paper, we propose an application-specific wear leveling technique, called Curling-PCM, to evenly distribute write activities across the PCM chip in order to improve the endurance of PCM. The basic idea is to exploit application-specific features in embedded systems and periodically move the hot region across the whole PCM chip. To further reduce the overhead of moving the hot region and improve the performance of PCM-based embedded systems, a fine-grained partial wear leveling policy is proposed in Curling-PCM, by which only part of the hot region is moved during each request handling period. The experimental results show that Curling-PCM can effectively evenly distribute write traffic in PCM chips compared with previous work. We expect this work can serve as a first step towards the full exploration of application-specific features in PCM-based embedded systems.