NMTSim: Transaction-Command Based Simulator for New Memory Technology Devices

To mitigate the impact of non-deterministic media access latencies in new memory technology devices, a recently proposed Non-Volatile Dual In-line Memory Module (NVDIMM) standard, NVDIMM-P uses novel out-of-order transaction commands. The previous DRAM simulators are unable to support this transaction protocol due to deterministic DDR timing. Also, existing NVDIMM simulators are customized for NAND flash memory, which are not generally applicable to emerging Non-Volatile Memory (NVM). In this letter, we present NMTSim, a transaction-command based and cycle accurate simulator for new memory technology devices. Strictly conforming to NVDIMM-P standard, NMTSim introduces a new memory controller with transaction handling and command issuing capabilities. To enable simulation for emerging NVM using DDR4 standard, we propose some new NVM timing parameters and incorporated them into DRAMSim2. Furthermore, DRAMSim2 is augmented with transaction handling and command scheduling logic to be the backend for the media controller. In addition, NMTSim incorporates an optimized transaction command issuing policy and an early notification mode to optimize access latency. We verify NMTSim using Intel Optane and characterize its performance using synthetic benchmarks with different read / write ratios.