DEMM: A Dynamic Energy-Saving Mechanism for Multicore Memories

Since main memory system contributes to a large and increasing fraction of server/datacenter energy consumption, there have been several efforts to reduce its power and energy consumption. DVFS schemes have been used to reduce the memory power, but they come with a performance penalty. In this work, we propose DEMM, an OS-based, high performance DVFS mechanism that reduces memory power by dynamically scaling individual memory channel frequencies/voltages. Our strategy also involves clustering the running applications based on their sensitivities to memory latency, and assigning memory channels to the application clusters. We introduce a new metric called Discrete Misses per Kilo Cycle (DMPKC) to capture the performance sensitivities of the applications to memory frequency modulation. DEMM allows us to save power in the memory system with negligible impact on performance. We demonstrate around 25% savings in the memory system energy and 10% savings in the total system energy, with only a 4% loss in workload performance.