Design and Implementation of Power-Aware Virtual Memory

Despite constant improvements in fabrication technology, hardware components are consuming more power than ever. With the ever-increasing demand for higher performance in highly-integrated systems, and as battery technology falls further behind, managing energy is becoming critically important to various embedded and mobile systems. In this paper, we propose and implement power-aware virtual memory to reduce the energy consumed by the memory in response to workloads becoming increasingly data-centric. We can use the power management features in current memory technology to put individual memory devices into low power modes dynamically under software control to reduce the power dissipation. However, it is imperative that any techniques employed weigh memory energy savings against any potential energy increases in other system components due to performance degradation of the memory. Using a novel power-aware virtual memory implementation, we estimate a significant reduction in memory power dissipation, from 4.1 W to 0.5-2.7 W, based on Rambus memory specifications, while running various real-world applications in a working Linux system. Unfortunately, due to a hardware bug in the chipset, direct power measurement is currently not possible. Applying more advanced techniques, we can reduce power dissipation further to 0.2-1.7 W, depending on the actual workload, with negligible effects on performance. We also show this work is applicable to other memory architectures, and is orthogonal to previously-proposed hardware-controlled power-management techniques, so it can be applied simultaneously to further enhance energy conservation in a variety of platforms.