POMI: Polling-Based Memory Interface for Hybrid Memory System

Modern conventional DRAM main memory system will no longer satisfy the growing demand for capacity and bandwidth on today’s data-intensive applications. Non-Volatile Memory (NVM) has been extensively researched as the alter-native for DRAM-based system due to its higher density and non-volatile characteristics. Hybrid memory system benefits from both DRAM and NVM technologies, however traditional Memory Controller (MC) cannot efficiently track and schedule operations for all the memory devices in heterogeneous systems due to different timing requirements and complex architecture supports of various memory technologies. To address this issue, we propose a hybrid memory architecture framework called POMI. It uses a small buffer chip inserted on each DIMM to decouple operation scheduling from the controller to enable the support for diverse memory technologies in the system. Unlike the conventional DRAM-based system, which relies on the main MC to govern all DIMMs, POMI uses polling-based memory bus protocol for communication and to resolve any bus conflicts between memory modules. The buffer chip on each DIMM will provide feedback information to the main MC so that the polling overhead is trivial. This gives several benefits: technology-independent memory system, higher parallelism, and better scalability. Our experimental results using octa-core workloads show that POMI can efficiently support heterogeneous systems and it outperforms an existing interface for hybrid memory systems by 22.0% on average for memory-intensive workloads.