Leveraging access port positions to accelerate page table walk in DWM-based main memory

Domain Wall Memory (DWM) with ultra-high density and comparable read/write latency to DRAM is an attractive replacement for CMOS-based devices. Unlike DRAM, DWM has non-uniform data access latency that is proportional to the number of shift operations. While previous works have demonstrated the feasibility of using DWM as main memory and have proposed different ways to alleviate the impact of shift operations, none of them have addressed the performance-critical metadata accesses, in particular page table accesses. To bridge this gap, this paper aims at accelerating page table walk in DWM-based main memory from two innovative aspects. First of all, we propose a new page table layout and leverage the positions of access ports in DWM to differentiate the state of page table entries. In addition, we propose a technique to pre-align the access ports to the positions to be accessed in the near future, thus hiding shift latency to the maximum extent. Since both address translation and context switching are affected by page table access latency, the proposed technique can effectively improve system performance and user experience.