iTRIM: I/O-Aware TRIM for Improving User Experience on Mobile Devices

TRIM is a recommended command to deliver data invalidation information of the file system to flash storage. It is issued on both system level and device level. Since it can reduce the number of data copies during device-level garbage collection (DGC), TRIM has been widely used to improve the endurance and performance of mobile devices. Contrary to the common belief, this work identifies that the default TRIM scheme has both merit and drawback to the performance of mobile devices, especially in flash-friendly file system (F2FS), which is a commonly used file system in mobile devices. On one hand, TRIM can reduce garbage collection migration to prolong the flash lifetime as well as improving I/O throughput; On the other hand, TRIM may induce I/O contentions. This article proposes a new TRIM scheme, iTRIM, to distribute the timing overheads to system idle time. To further reduce I/O contention and improve I/O performance, the design of iTRIM considers the TRIM size, and the logical addresses' pattern of victim invalidated data. Experimental results show that iTRIM can minimize I/O contentions while retaining the benefits of the default TRIM scheme for endurance and performance.