Enhanced UBI layer for fast boot-up times of mobile consumer devices

摘要

Due to its short mounting time, the Unsorted Block Image File System (UBIFS) allows mobile consumer devices to boot up faster than devices with other existing flash file systems. However, UBIFS requires a preceding UBI image attachment, which is not scalable. This due to the fact that two pages have to be read per erase block of the UBI image during mounting process, including an erase counter (EC) header and volume ID (VID) header. To lessen the effect of this problem, the UBI attachment process is modified. The EC header scan is delegated to a kernel thread after the booting process. And using software error-correcting code (ECC) instead of hardware ECC, latency from the VID header scan is lightened. As a result, although still not scalable, the mounting time is shortened considerably. In addition, the coefficient (rate of increase) becomes less significant. In experiments, the mounting time is under 1/8 of the normal time with a 100MB UBI Image. In addition, the rate of increase in the mounting time according to the UBI image size, i.e., the coefficient, is lessened from 8.9 to 0.5 milliseconds per byte.