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As more consumer electronics adopt monolithic kernels, NAND flash memory is used for the swap space in virtual memory systems. While flash memory has the advantages of low-power consumption, shock-resistance and non-volatility, it requires garbage collection due to its erase-before- write characteristic. The efficiency of the garbage collection scheme largely affects the performance of flash memory. This paper proposes a novel garbage collection technique which exploits data redundancy between the main memory and flash memory in flash memory-based virtual memory systems. Compared to the previous approach, our proposed scheme takes into consideration the locality of data to minimize the garbage collection overhead. In addition, by considering the computational overhead of the garbage collection algorithm, we also propose an adaptive scheme which can minimize the computational overhead with marginal I/O performance degradation. Experimental results demonstrate that the proposed garbage collection scheme improves performance by 37% on average compared to those of previous schemes.
Date of Publication: November 2010