HMMSim: a simulator for hardware-software co-design of hybrid main memory

Due to scalability and energy consumption, the use of DRAM as the only main memory technology in modern computers is becoming increasingly less appealing. Researchers have proposed combining DRAM and non-volatile memory (NVM) in main memory to increase capacity and reduce energy consumption. Due to its architectural simplicity, software-managed hybrid memory is a promising way to incorporate NVM. However, there are significant performance issues caused by increased memory traffic due to data migration and a lack of effective migration policies. These issues can be addressed by carefully co-designing hardware-software mechanisms and migration policies. To aid in the development of new mechanisms and policies to incorporate NVM in main memory, we present HMMSim, a trace-driven simulator that allows for fast and flexible exploration of the hardware-software co-design space of hybrid main memory. HMMSim has a simple interface to connect memory hierarchy components that can be configured to simulate several memory architectures, including DRAM only, NVM only, DRAM hardware cache, and software-managed hybrid memory. We present two case studies that use HMMSim, and show that HMMSim is fast, flexible and scalable.