Operand-Oriented Virtual Memory Support for Near-Memory Processing

Abstract

Virtual memory support is one of the major challenges of near-memory processing (NMP). Many previous works focused on this issue, but there are practical limitations that conventional CPU hardware or memory allocation schemes should be modified. Another technique uses a specialized page table for NMP to avoid such limitations. However, the previous work proposed NMP-specific page table that has static page table walk latency regardless of data size. This causes unnecessarily long address translation time for relatively small data. In this paper, we propose an operand-oriented technique for virtual memory support. Our scheme does not pre-determine the size of shared space; rather, it allocates shared space depending on the size of operands data for NMP. Then, we significantly reduce page table walk latency by using our flexible page table, which adapts the page table hierarchy to the size of shared spaces. To prove our concept, we implement our scheme in a full-system simulator and an FPGA-based verification platform. We then compared it with CPU's page table and the previous NMP-specific page table. The experimental results show that our technique outperforms page table walk latency by 69.3 percent and 43.8 percent compared to the CPU's page table and the comparison, respectively.