Garbage collection schemeoptimization in YAFFS

Abstract

In this project we present an improved garbage collection scheme for YAFFS2 (Yet Another Flash File System). Our objective was to reduce the number of Aggressive Garbage Collections in Garbage Collection module of YAFFS2. We explore the various values of beta (ratio of number of erased chunks to number of free chunks) experimentally and try to find the optimal value of beta for which number of Aggressive Garbage Collections (Garbage Collection) is the least. Extensive tests were conducted by varying the value of beta (0< beta<1). A total of three tests were used to determine the number of Garbage Collections in different scenarios: a write test (clean write as well as overwrites), an erase test and a post erase test Garbage Collection monitoring test. A generic write test and an erase test were provided with YAFFS2 source code, which needed little modifications. The last test was developed by us as the situation demanded. Reduction in the number of Aggressive Garbage Collections reduces computational load on the processor, which in turn saves power, especially in battery powered devices.