A cost-aware page replacement algorithm for NAND flash based mobile embedded systems
A cost-aware page replacement algorithm for NAND flash based mobile embedded systems
复制标题
基于 NAND 闪存的移动嵌入式系统的成本感知页面替换算法
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
H. Bahn
中科院分区：
文献类型：
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作者：
Junseok Park;Hyejeong Lee;S. Hyun;K. Koh;H. Bahn
NAND闪存在手机、数码相机等移动嵌入式系统中被广泛用作辅助存储。这些系统通常采用压缩文件系统(CFS)来存储在设计阶段固定的系统文件，并与常规文件系统相结合来存储数据文件。由于从CFS检索页面需要额外的解压缩时间，因此在做出页面替换决策时授予它们更高的优先级是合理的。本文针对基于NAND闪存的嵌入式系统提出了一种新的页面替换算法，该算法考虑了各页面的非对称操作开销。该算法考虑了CFS页面的解压缩开销以及闪存中读写的非对称I/O开销。为此，该算法根据不同的操作成本将存储空间划分为读取区、写入区和压缩区。然后，根据访问模式的变化和对降低I/O成本的贡献，动态调整每个区域的大小。跟踪驱动的仿真结果表明，该算法显著提高了移动嵌入式系统的I/O性能。具体地说，与公认的时钟、CAR和CFLRU等算法相比，它将I/O时间减少了4.8-53.3%。
NAND flash memory is widely used as secondary storage in mobile embedded systems such as cellular phones and digital cameras. These systems usually employ a compressed file system (CFS) to store system files which are fixed during the design phase, in combination with a normal file system to store data files. Since retrieving pages from a CFS requires additional decompression time, it is reasonable to grant them higher priorities when making a page replacement decision. In this paper, we present a new page replacement algorithm for NAND flash memory based embedded systems that considers asymmetric operation cost of each page. The proposed algorithm considers the decompression cost of a page from CFS as well as the asymmetric I/O costs of reads and writes in flash memory. To do this, the algorithm partitions the memory space into a read area, a write area, and a compressed area depending on different operation costs. The size of each area is then dynamically adjusted based on the change of access patterns and the contribution to reducing the I/O costs. Trace-driven simulations show that the proposed algorithm improves the I/O performance of mobile embedded systems significantly. Specifically, it reduces I/O time by 4.8-53.3% compared to widely acknowledged algorithms such as CLOCK, CAR, and CFLRU.