Microscope on Memory: MPSoC-Enabled Computer Memory System Assessments
Abhishek Kumar Jain, Scott Lloyd, Maya B. Gokhale · 2018
Recent advances in new memory technologies and packaging options has focused attention on computer memory system design and evaluation. Examples include high bandwidth memories such as Hybrid Memory Cube and HBM, and 3DXPoint non-volatile memory. Emerging memories display a wide range of bandwidths, latencies, and capacities, making it challenging for the computer architect to navigate the design space of potential memory configurations, and for the application developer to assess performance implications of using such memories. In this work, we describe the Logic in Memory Emulator (LiME), a hardware/software tool specially designed for memory system evaluation and experiment. LiME uses the Xilinx Zynq UltraScale+ MPSoC on the ZCU102 board to capture any/all memory access, either from the Processing System (PS) or the Programmable Logic (PL). LiME employs novel loopback circuitry in conjunction with address map relocation to pass memory references from the PS into the PL side. The memory request is looped back into the PS DRAM memory controller and concurrently processed by LiME. We have demonstrated four high value use cases: full external memory access logging and replay, emulation of various memory system latencies by passing the memory request through delay registers before entering the PS memory subsystem, emulation of acceleration engines that can independently access memory, and performance comparison of two CPU architectures with respect to their memory behavior. In this paper we will describe this novel application of state-of-the-art MPSoC embodied by the LiME framework and highlight its uses.