基于LIRS的YAFFS2元数据缓存管理机制设计

Design of Metadata Cache Management Scheme for YAFFS2 Based on LIRS

由于闪存采取异地更新机制,文件操作过程中伴随着大量的元数据修改操作,YAFFS2文件系统是以同步的方式更新元数据,这样就会带来大量的无效object header,降低系统I/O性能。使用缓存是解决这一问题的有效方法,缓存置换算法决定着缓存管理的效率,文章在已有研究的基础上简化了元数据缓存管理机制,并提出了基于缓存状态信息的LIRS-P算法,该算法保留了LIRS捕获弱局部性数据的特点,同时结合文件系统特点和闪存特性,优先置换出对文件系统可靠性影响较大,I/O开销较小的缓存页。实验结果表明,LIRS-PP提高了元数据缓存的管理效率,进而提高了文件系统的I/O性能。

With the out-of-place update mechanism of flash,the writing process is accompanied by a large number of metadata modification operations. Whereas,YAFFS2 file system updates metadata synchronously,which will produce a lot of invalid object headers,and thus reduce the system I / O performance. Caching is an effective way to solve this problem,and the cache replacement algorithm determines the management efficiency. On the basis of existing research,this paper simplifies the metadata cache management mechanism and proposes LIRS-P algorithm based on cache status information. The algorithm preserves the features of LIRS,which is senstive to the access partterns with weak locality. Considering the characteristics of the file system and flash features,the scheme preferentially replaces the caches having greater impact on the reliability of the file system,and lower I /O overhead. The results show that LIRS-P improves metadata cache management efficiency,thereby increasing the I / O performance of the file system.