WAM: Wear wear-out-aware memory management for SCRAM-based low power mobile systems

Emerging storage class RAM (SCRAM) devices are power-efficient, byte-addressable, and non-volatile. However, each SCRAM memory cell has a limited lifetime. To use SCRAM to replace power-hungry DRAM in mobile consumer devices, wear-leveling among cells will be a critical issue. Especially, due to the locality of memory access pattern, current operating systems' SCRAM-unaware memory allocator may intensify the wear of certain SCRAM blocks. Wear-leveling requires the redesign of operating systems to distribute memory accesses evenly throughout the entire memory space. This paper suggests two operating- systemlevel wear-leveling techniques for SCRAM devices. First, this paper proposes a novel memory allocator, called W-Buddy, that considers the wear of memory chunks as it selects a free memory chunk to be allocated. Second, this paper proposes a variable metadata formatting technique for file systems. The experiment results show that the proposed W-Buddy allocator and metadata reformatting technique improve the lifetime of SCRAM devices compared with the techniques of conventional operating systems.