Lazy TRIM: Optimizing the Journaling Overhead caused by TRIM commands on Ext4 File System

Nowadays, NAND flash storage devices have become a standard for secondary storage in consumer electronics devices. Unfortunately, TRIM command for the flash storage causes journaling overhead on the ext4 file system. In this paper, to figure out the root cause of the overhead, we study the relationship between ordered mode journaling and the TRIM command. Then, we propose a novel scheme, called lazy TRIM, that adopts multi-threading in background to gracefully distribute the journaling overhead caused by the TRIM command. Our evaluation results clearly confirm that lazy TRIM improves the latency of the fsync system call by up to 99% compared with the conventional scheme.