CELF Project Proposal/UBIFS mount time speedups


 * Summary : Improve UBIFS mounting time


 * Proposer : Tim Bird, Kyungmin Park

Description
UBIFS is a next-generation flash-based file system for Linux. It is a read/write file system, which supports compression and has good performance. However, it's mount times are not very good. This affects overall Linux boot time, for a UBIFS-based embedded system.

The purpose of this project would be to investigate mount performance issues, and try to resolve them. One suggestion is to keep the bad block table on flash, instead of re-scanning it on every boot. It is not known if algorithms to do this are covered by existing flash management patents.

Related work

 * UBIFS
 * http://en.wikipedia.org/wiki/UBIFS
 * http://lwn.net/Articles/276025/
 * UBI2
 * see portions of http://www.mjmwired.net/kernel/Documentation/filesystems/ubifs.txt
 * Mount times
 * http://osl.sed.hu/wiki/ubifs/index.php/Mount_results
 * http://elinux.org/images/f/f8/CELFJamboree30-UBIFS_update.pdf


 * Scope : This project might take about 4 months

Comments
Toshiba may already be working on this project.

Kyungmin Park writes:

Description: UBI scans all physical block at boot time. and maintain it at RAM. Usually this scan time takes almost 2 or more seconds. To reduce the this time UBI maintain block mapping information on flash and use it at next boot time.

Also it have to support or provide rescan mechanism at runtime to use single image into another flash

http://www.mjmwired.net/kernel/Documentation/filesystems/ubifs.txt
 * UBI2
 * see portions of