Combining Emulation and Simulation to Evaluate a Near Memory Key/Value Lookup Accelerator.

Processing large numbers of key/value lookups is an integral part of modern server databases and other Big Data applications. Prior work has shown that hash table based key/value lookups can benefit significantly from using a dedicated hardware lookup accelerator placed near memory. However, previous evaluations of this design on the Logic in Memory Emulator (LiME) were limited by the capabilities of the hardware on which it was emulated, which only supports a single CPU core and a single near-memory lookup engine. We extend the emulation results by incorporating simulation to evaluate this design in additional scenarios. By incorporating an HMC simulation model, we design optimizations that better mitigate the effects of the HMC closed page policy and that better utilize the HMC's parallelism, improving predicted performance by an order of magnitude. Additionally, we use simulation to evaluate the scaling performance of multiple near-memory lookup accelerators. Our work employs an open source emulator LiME, open source simulatation infrastructure SST, and the open source HMC-Sim simulator.