Geun-sik Lim

BB: booting booster for consumer electronics with modern OS

Unconventional computing platforms have spread widely and rapidly following smart phones and tablets: consumer electronics such as smart TVs and digital cameras. For such devices, fast booting is a critical requirement; waiting tens of seconds for a TV or a camera to boot up is not acceptable, unlike a PC or smart phone. Moreover, the software platforms of these devices have become as rich as conventional computing devices to provide comparable services. As a result, the booting procedure to start every required OS service, hardware component, and application, the quantity of which is ever increasing, may take unbearable time for most consumers. To accelerate booting, this paper introduces Booting Booster (BB), which is used in all 2015 Samsung Smart TV models, and which runs the Linux-based Tizen OS. BB addresses the init scheme of Linux, which launches initial user-space OS services and applications and manages the life cycles of all user processes, by identifying and isolating booting-critical tasks, deferring non-critical tasks, and enabling execution of more tasks in parallel. BB has been successfully deployed in Samsung Smart TV 2015 models achieving a cold boot in 3.5 s (compared to 8.1 s with full commercial-grade optimizations without BB) without the need for suspend-to-RAM or hibernation. After this successful deployment, we have released the source code via http://opensource.samsung.com/, and BB will be included in the open-source OS, Tizen (http://tizen.org/).

Enhancing init scheme for improving bootup time in mobile devices

The init process has evolved as a system and service manager of process scheduling, input/output scheduling, memory scheduling, and the creation and termination of processes. The addition of software functionality increases software complexity. In a mobile environment, the increase of software complexity results in a slow boot time for mobile devices. This paper describes a mobile aware bootup framework by isolating the dependencies of the execution sequence among the processes, and by simplifying the existing init scheme to accelerate the boot time of the mobile device. From our experiment, our proposed approaches reduce the bootup time of the mobile device by about 50%.

User-level memory scheduler for optimizing application performance in NUMA-based multicore systems

Multicore CPU architectures have been established as a structure for general-purpose systems for high-performance processing of applications. Recent multicore CPU has evolved as a system architecture based on non-uniform memory architecture. For the technique of using the kernel space that shifts the tasks to the ideal memory node, the characteristics of the applications of the user-space cannot be considered. Therefore, kernel level approaches cannot execute memory scheduling to recognize the importance of user applications. Moreover, users need to run applications after sufficiently understanding the multicore CPU based on non-uniform memory architecture to ensure the high performance of the users applications. This paper presents a user-space memory scheduler that allocates the ideal memory node for tasks by monitoring the characteristics of non-uniform memory architecture. From our experiment, the proposed system improved the performance of the application by up to 25% compared to the existing system.

Preemptibility-aware responsive multi-core scheduling

We propose a novel responsive scheduling technique to minimize the scheduling latency of a real-time process in the multi-core architecture, called the preemptibility-aware scheduling (PAS). Modern complex operating systems contain numerous long interrupt-disabled and non-preemptible sections, and consequently these sections obstruct the immediate handling of urgent interrupts and the rapid scheduling of interrupt-driven real-time tasks, causing significant latency between interrupt arrival and process scheduling. The proposed PAS guarantees that before an urgent interrupt occurs, at least one among multiple CPU cores is always in both interrupt-enabled and preemptible sections, so that the incoming urgent interrupt can always be handled with no significant delay by such CPU core. Experimental results show that the worst-case latency can be reduced by 27-96%.

Cloud-based content cooperation system to assist collaborative learning environment

Online educational systems running on smart devices have the advantage of allowing users to learn online regardless of the location of the users. In particular, data synchronization enables users to cooperate on contents in real time anywhere by sharing their files via cloud storage. However, users cannot collaborate by simultaneously modifying files that are shared with each other. In this paper, we propose a content collaboration method and a history management technique that are based on distributed system structure and can synchronize data shared in the cloud for multiple users and multiple devices.