Energy-aware flash memory management in virtual memory system
Resource
IEEE Transactions on Very Large Scale Integration (VLSI) Systems 16 (8): 952-964
Journal
IEEE Transactions on Very Large Scale Integration (VLSI) Systems
Journal Volume
16
Journal Issue
8
Pages
952-964
Date Issued
2008
Author(s)
Abstract
The traditional virtual memory system is designed for decades assuming a magnetic disk as the secondary storage. Recently, flash memory becomes a popular storage alternative for many portable devices with the continuing improvements on its capacity, reliability and much lower power consumption than mechanical hard drives. The characteristics of flash memory are quite different from a magnetic disk. Therefore, in this paper, we revisit virtual memory system design considering limitations imposed by flash memory. In particular, we focus on the energy efficient aspect since power is the first-order design consideration for embedded systems. Due to the write-once feature of flash memory, frequent writes incur frequent garbage collection thereby introducing significant energy overhead. Therefore, in this paper, we propose three methods to reduce writes to flash memory. The HotCache scheme adds an SRAM cache to buffer frequent writes. The subpaging technique partitions a page into subunits, and only dirty subpages are written to flash memory. The duplication-aware garbage collection method exploits data redundancy between the main memory and flash memory to reduce writes incurred by garbage collection. We also identify one type of data locality that is inherent in accesses to flash memory in the virtual memory system, intrapage locality. Intrapage locality needs to be carefully maintained for data allocation in flash memory. Destroying intrapage locality causes noticeable increases in energy consumption. Experimental results show that the average energy reduction of combined subpaging, HotCache, and duplication-aware garbage collection techniques is 42.2%. © 2008 IEEE.
Subjects
Embedded systems; Energy-efficient; NAND flash memory; Virtual memory
SDGs
Other Subjects
Conservation; Data storage equipment; Disks (structural components); Embedded systems; Energy efficiency; Energy policy; Integrated circuits; Magnetic disk storage; Magnetic storage; Mechanical drives; Nonvolatile storage; Refuse collection; Refuse disposal; Waste disposal; Average energy; Data allocation; Data locality; Data redundancies; Design considerations; Energy consumption.; Energy-aware; Energy-efficient; First orders; Garbage collection; Hard drives; Lower-power consumption; Magnetic disks; Main memories; NAND flash memory; Portable devices; Secondary storage; Virtual memory; Write-once; Flash memory
Type
journal article
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