• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.11-19
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• 2022

In this paper, we propose a fault tolerant embedded system using memory redundancy on the full-virtualization based virtual machine monitor. The proposed virtual machine monitor first virtualizes main memory of embedded system utilizing efficient shadow page table scheme so that the embedded system runs as a virtual machine on the virtual machine monitor. The virtual machine monitor makes the backup of the embedded system run as another virtual machine by copying memory contents of the embedded system into memory space of backup system according to predefined schedules. When an error occurs in the target virtual machine, the corresponding standby virtual machine takes the role of target virtual machine and continues its operation. Performance evaluation studies show that such backups and switches of virtual machines are performed with minor performance degradation.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.57-64
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• 2009

Recently virtualization has been one of the most popular research topics in system software area. While there already exist many commercial virtualization products for general-purpose computer system, little efforts are made to virtualize embedded system. In this paper, we design and implement a virtual machine monitor which divides each physical hardware resource of a embedded system into logical ones and reorganizes them into many virtual machines, which result in running several real-time operating systems concurrently on a single embedded system. We measure various performance metrics of the virtual machine monitor developed on a real embedded system. The results of the study show that our virtual machine monitor has enough potentiality of its application to real-world embedded systems.

• Journal of the Korea Society of Computer and Information
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• v.22 no.6
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• pp.1-8
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• 2017

In this paper, we propose a fault tolerance technique which enables embedded systems to run without interruption while its operating system and tasks fail. In order to improve reliability, the proposed scheme makes an embedded system run as a virtual machine on virtual machine monitor. It also prepares a contingency virtual machine at which periodical backups of the embedded system are saved. When an error occurs in the main virtual machine, the corresponding standby virtual machine takes a role of the main virtual machine and continues its operation. Especially such backups and switches of virtual machines are performed with minor performance degradation by manipulating page table entries in virtual machine monitor. By conducting performance evaluation studies, we show that the proposed scheme makes embedded system robust against errors while it does not degrade the performance of the system significantly.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.770-771
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• 2009

리눅스 커널을 VMM(Virtual Machine Monitor)로 만들어 주는 KVM의 메모리 관리 기법을 분석한다. Xen과의 차이점과 KVM의 구조를 알아보고 KVM에서의 메모리 관리 기법에 대해 분석하였다. 또한 CPU의 가상화 기능인 Intel VT-x가 어떻게 적용되었는지 분석한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.14-19
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• 1998

The purpose of our study is to develop tool kits which give us inexpensive simulation method. We develop a Programmable Logic Controller (PLC) program module with which we can edit and monitor PLC program, a virtual PLC (VPLC) system and simulation equipment. The PLC and simulation equipment are interlinked each other and controlled by the PLC program in real time. So, e can get effect as actural operation. Using our new tool kits we don't have to prepare PLC and machine, because we can configure PLC system and see the response of virtual machine n monitor. For validity of the developed program, we make experiments for the PLC program of elevator and automatic materials weighting system. The experimental results show that the virtual machine (VM) operates properly by the PLC control program.

• Smart Media Journal
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• v.5 no.4
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• pp.18-25
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• 2016

Virtualized hardware resources provides efficiency in use and easy of management. Based on the benefits, virtualization techniques are used to build large server clusters and cloud systems. The performance of a virtualized system is significantly affected by the virtual machine scheduler. However, the existing virtual machine scheduler have a problem in that the I/O response is reduced in accordance with the scheduling delay becomes longer. In this paper, we introduce the Loan/Redemption mechanism of a virtual machine scheduler in order to improve the responsiveness to I/O events. The proposed scheme gives additional credits for to virtual machines and classifies the task characteristics of each virtual machine by analyzing the credit consumption pattern. When an I/O event arrives, the scheduling priority of a virtual machine is temporally increased based on the analysis. The evaluation based on the implementation shows that the proposed scheme improves the I/O response 60% and bandwidth of virtual machines 62% compared to those of the existing virtual machine scheduler.

• IEMEK Journal of Embedded Systems and Applications
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• v.8 no.3
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• pp.145-153
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• 2013

Virtualization technology has been applied in IA-32 based server or desktop systems. Recently it has been applied in ARM based mobile systems. Virtualization technology provides many useful features that are not possible in operating system level such as isolation, interposition, encapsulation and portability. In this research, we implement an ARM based VMM(Virtual Machine Monitor) by using the following techniques. First, we use "emulation" to virtualize the processor. Second, we use "shadow page tables" to virtualize the memory. Finally, we use a simple "pass-through I/O" to virtualize the device. Currently the VMM runs ARM Linux kernel 3.4.4 on a BeagleBoard-xM, and we evaluated the performance of the VMM using lmbench and dhrystone. The result of the evaluation shows that our VMM is slower than Xen on ARM that is implemented using paravirtualization but has good performance among the VMMs using full-virtualization.

• Journal of the Korea Society of Computer and Information
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• v.17 no.9
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• pp.127-138
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• 2012

In this paper, we present a tool (named VMBootFailMonitor) to detect and analyze a failure of a VM boot creation caused by faults on virtual disks of a Xen-based VM. Also, we presents an architecture and detail analysis process of the virtual disk faults in our tool. Especially, VMBootFailMonitor provides a causual analysis result for a case of VM creation failure based on three modules which performs virtual disk analysis, virtualized system analysis and system log analysis. We also support a comparison result between boot times of normal VMs and fault detection times of VM creation based on abnormal virtual disks. At result, our tool detects VM boot failures (3~6 seconds) within normal VM boot times (8~16 seconds).

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2899-2902
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• 2003

Mobile communication is one of the fastest growing industries in the world and especially in Korea, where we have well over 30 million voice subscribers. Mobile communication now offers variety of data communication services such as wireless internet, multimedia messages, and color graphic displays. Handsets also have grown to accommodate such services, thus with functionalities such as programmable virtual machines that users can download and execute their own programs. In this paper, we have demonstrated a PCS handset monitoring system which can monitor biometry signals - in this case ECG over wireless internet and wireless data network (IS95C) based on programmable virtual machine architecture. The remote client handset receives data signals from a centralized server and processes and displays them in human friendly form in real time. Since every single handset on sales in Korea has programmable virtual machine and more than 10 million handsets are in distribution already, proper applications may have substantial impact on the related fields.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.6
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• pp.385-393
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• 2017

As the use of mobile devices such as smartphones increases, there is growing interest on the benefits of virtualization in embedded systems. Full virtualization has the advantage of running the guest virtual machine without modifying the guest operating system. However, full virtualization suffers slow execution speed due to the cost of context switching between the virtual machines and the virtual machine monitor. In this paper, we propose a translated block and context switching optimization to improve the guest execution speed in the embedded system. As a result, the improved dynamic binary translator is up to 5.95 times faster than the native execution. Performance degradation is less than that of the other virtualization system.