July 13th-16th, 2010
Ottawa Westin
Ottawa, Canada

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Boosting up Embedded Linux device: experience on Linux-based Smartphone

Modern smartphones have extensive capabilities and connectivities, comparable to those of personal computers (PCs). As the number of smartphone features increases, smartphone boot time also increases, since all features must be initialized during the boot time. Many fast boot techniques have focused on optimizing the booting sequence. However, it is difficult to obtain quick boot time (under 5 seconds) using the fast boot techniques, and many parts of the software platform require additional optimization. An intuitive way to obtain instant boot times, while avoiding these issues, is to boot directly from hibernation. We apply hibernation-based techniques to a Linux-based smartphone, and thereby overcome two major obstacles: long loading times for snapshot image and maintenance costs related to hardware change.

We propose two mechanisms, based on hibernation, to obtain outstanding reductions in boot time. First, minimize the size of snapshot image via page reclamation, which reduces the load time of image. Snapshot is split into two major segments: essential-snapshot-image and supplementary-snapshot-image. The essential snapshot image is a minimally-sized image used to run the Linux kernel and idle screen, and the supplementary-snapshot-image contains the remained that could be restored on demand. Second, we add additional device information to the essential-snapshot-image, which is used when the the device is reactivated upon booting up. As a result, our mechanism omits some time-consuming jobs related to device re-initialization and software state recovery. In addition to quick boot times, our solution is low maintenance. That is, while the snapshot boot is implemented in the bootloader, our solution utilizes the kernel infrastructure because it is implemented in the kernel. Therefore, there is little effort required, even when the target hardware is changed. We prototyped our quick boot solution using a S5PC110-based smartphone. The results of our experiments indicate that we can obtain get dramatic gain in performance in a practical manner using this quick boot solution.

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