基于逻辑区间热度的NAND闪存垃圾回收算法

Garbage collection algorithm for NAND flash memory based on logical region heat

针对现有的NAND闪存垃圾回收算法中回收性能不高,磨损均衡效果差,并且算法内存开销大的问题,提出了一种基于逻辑区间热度的垃圾回收算法。该算法重新定义了热度计算公式,把连续逻辑地址的NAND内存定义为一个热度区间,以逻辑区间的热度来代替逻辑页的热度,并将不同热度的数据分开存储到不同擦除次数的闪存块上,有效地实现了数据冷热分离,并且节约了内存空间。同时,算法还构造了一种新的回收代价函数来选择回收块,在考虑回收效率的同时,还兼顾了磨损均衡的问题。实验结果表明,该算法与性能优异的FaGC算法相比,总的擦除次数减少了11%,总的拷贝次数减少了13%,擦次数最大差值减少了42%,内存消耗能减少了75%。因此,该算法有利于增加闪存可用空间,改善闪存系统的读写性能,延长闪存使用寿命。

To solve the problems of low collection performance, poor wear leveling effect, and high memory overhead in the existing NAND flash memory garbage collection algorithms, a new garbage collection algorithm based on logical region heat was proposed. The heat calculation formula was redefined, the NAND memory of continuous logical address was defined as a heat range which was used to replace the heat of logical page, then the data with different heat was separated into the corresponding flash blocks with different erase counts. The cold and hot data were effectively separated,and the memory space was also saved. Meanwhile, a new collection cost function was constructed to improve the collection efficiency and wear leveling effect. The experimental results showed that compared with the excellent File-aware Garbage Collection（FaGC）algorithm, the total number of erase operations was reduced by 11%, the total number of copy operations was reduced by 13%, the maximum difference of erase counts was reduced by 42%, and the memory consumption was reduced by 75%.Therefore, the available flash memory space can be increased, the read and write performance of flash memory can be improved, and the flash memory life can be also extended by using the proposed algorithm.