Rank-Aware Dynamic Migrations and Adaptive Demotions for DRAM Power Management (Supplementary File)

A.1 Studies on Dynamic Migrations We study the impact of dynamic migrations, comparing RAMZzz and RZ–SP (RZ–SP uses the adaptive demotion scheme with no page migration). Figure 1 presents ED results for RAMZzz and RZ–SP on DDR3. RAMZzz has much lower ED than RZ–SP, with an average reduction of 23.3%. The reduction depends on the memory footprint and memory access intensiveness. The reduction is more significant on memoryintensive workloads (such as M4) or workloads with small memory footprint (such as S3 and S4). If a workload has a small memory footprint, the page migration has a small overhead on both the delay and the energy consumption, and the portion of cold ranks is higher. If the memory access of a workload is more intensive, many idle periods are too short and RZ–SP has less opportunities for saving background power (even with our proposed adaptive demotion scheme). On those two kinds of workloads, page migration is important for the effectiveness of power management. In contrast, when the memory access is less intensive or has a large memory footprint, RZ–SP is quite competitive to RAMZzz. The example workloads include S1 and M2.