Exploring Skyrmion Racetrack Memory for High Performance Full-Nonvolatile FTL

Skyrmion racetrack memory (SK-RM) has shown great potential for replacing DRAM or SRAM with its high density and great access performance. Unlike other non-volatile random access memory (NVRAM), SK-RM supports random updates through injecting or removing skyrmions on a racetrack. Injected skyrmions can be shifted along the racetrack to store data. Nevertheless, since most previous studies focus on minimizing the number of inject or shift operations, the unique feature of moving skyrmions vertically between racetracks and the possibility of utilizing free or invalid memory space to preserve skyrmions receive much less attention. In this paper, we observe that vertical movement and preservation of skyrmions provide a great opportunity to mitigate the possible run time performance degradation issue of NVRAM-based flash translation layer (FTL), as writes of mapping entries typically induce more overhead than reads on NVRAM. To fully exploit the benefits of SK-RM within the FTL mechanism, this paper proposes an SK-FTL to enable a high-performance and non-volatile FTL by preserving and reforming skyrmions over multiple data writes. Experimental results suggest that SK-FTL can effectively improve the performance of non-volatile FTL.