基于NAND Flash的嵌入式内存数据管理算法研究

发布时间：2018-03-04 08:35

本文选题：嵌入式系统　切入点：NAND　出处：《中南大学》2013年硕士论文　论文类型：学位论文

【摘要】：摘要：在会议评审辅助支撑系统中海量数据的存取对嵌入式终端的性能提出了很高的要求,尤其需要大量数据快速读写,并保证有较高的可靠性,而应用于嵌入式系统的闪存芯片本身具有读写不平衡和异地更新等特点,需要进行系统的数据管理研究。论文针对实际问题提出了基于热度优先级的改进置换算法,以及基于该算法的两级cache映射粒度交换的FTL(闪存转换层)算法-CEFTL。该算法将NAND闪存划分为数据块和转换块,页映射表保存在转换块,地址映射机制则采用块映射和页映射两种不同的粒度,通过全局转换字典(GTD)进行交换,从而提高cache命中率。通过研究LRU-WSR算法,论文借鉴其中提出的冷热检测算法,并对LRU-WSR的置换划分进行改进,根据访问数据在NAND闪存存储中的访问频率和存储特点将数据块标记成四种不同优先级级别,通过这种优先级的划分构建两级置换算法,以此解决NAND闪存中数据访问的特殊性带来的置换开销。论文以两级置换算法为基础构建CEFTL映射算法,针对RFTL算法在可靠性和磨损均衡上的不足,改变其混合映射中页映射存储位置,借鉴CDFTL提出的两级cache机制,减少RAM空间消耗,从而使OOB可存储码长更长的BCH校验码,提高可靠性。对RFTL的分段垃圾回收策略中的交换操作和移位操作进行改进,加入基于热度的块映射交换,使系统在运行过程中,闪存物理块的擦除次数相近。通过优先级置换的策略,使CEFTL的系统平均响应时间接近RFTL的最佳响应时间。
[Abstract]:Absrtact: the access of massive data in the conference review support system requires high performance of embedded terminals, especially requires a large number of data to read and write quickly, and to ensure high reliability. The flash memory chip used in the embedded system has the characteristics of unbalanced reading and writing and remote updating, so it is necessary to study the data management of the system. In this paper, an improved permutation algorithm based on heat priority is proposed to solve practical problems, and an FTL (flash memory conversion layer) algorithm based on two-level cache mapping granularity exchange is proposed. The algorithm divides NAND flash memory into data blocks and conversion blocks. The page mapping table is stored in the translation block, and the address mapping mechanism uses block mapping and page mapping two different granularity, which is exchanged by the global translation dictionary, so as to improve the hit rate of cache. By studying the LRU-WSR algorithm, this paper uses the proposed cold and heat detection algorithm for reference, and improves the permutation partition of LRU-WSR. According to the access frequency and storage characteristics of access data in NAND flash memory, the data block is marked into four different priority levels. In this way, the permutation overhead caused by the particularity of data access in NAND flash memory is solved. In this paper, we construct CEFTL mapping algorithm based on two-level permutation algorithm. Aiming at the deficiency of RFTL algorithm in reliability and wear equalization, we change the storage location of page mapping in its hybrid mapping, draw lessons from the two-level cache mechanism proposed by CDFTL, and reduce the space consumption of RAM. So that OOB can store longer code length BCH check code, improve the reliability, improve the switching operation and shift operation in the section garbage collection strategy of RFTL, add block mapping exchange based on heat, make the system run in the process. The average response time of CEFTL system is close to the optimal response time of RFTL.
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

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