Energy and Performance Optimization of Demand Paging With OneNAND Flash

New fusion memory devices consisting of multiple heterogeneous memory components in a single die or package offer efficient ways to optimize embedded systems in terms of energy, performance, and cost. Samsung Electronics recently announced the OneNAND fusion memory, in which a NAND flash array is integrated with dual SRAM buffers to provide a nor-type I/O interface. OneNAND has the low cost and large capacity of a NAND flash but also permits eXecution-in-Place (XIP) like a nor flash. The deployment of such devices requires careful system-level resource management because of their impact on energy consumption and performance, and existing memory optimization techniques, such as the demand paging used with NAND flash, may no longer be appropriate for systems with a fusion memory. We introduce a new online demand paging scheme that fully exploits the XIP capability of OneNAND flash by classifying pages as load preferred (residing in the on-chip SRAM) and XIP preferred (accessed directly from the OneNAND flash and discarded after use). This achieves, on average, a 26% reduction in energy consumption and a 19% increase in performance, compared with conventional NAND flash demand paging.