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Improving the startup time of digital TV
Heeseung Jo,Hwanju Kim,Hyun-Gul Roh,Joonwon Lee IEEE 2009 IEEE transactions on consumer electronics Vol.55 No.2
<P>Digital TV was introduced with promises for higher quality displays and converging Internet services which require more computing power and complex software systems. Such complexity entails a prolonged startup time that is similar to booting a computer system. In this paper, we propose two approaches to reduce the startup time of digital TV. Based on the suspend-resume technique employed in many commodity operating systems, our mechanisms replace the cold startup process of digital TV with the resuming from a suspend image. We also analyze the bottlenecks in the startup process and suggest hardware supports to improve the startup time. The proposed approaches reduce the startup time of digital TV by about 50%.</P>
Transparent Fault Tolerance of Device Drivers for Virtual Machines
Heeseung Jo,Hwanju Kim,Jae-Wan Jang,Joonwon Lee,Seungryoul Maeng IEEE 2010 IEEE Transactions on Computers Vol.59 No.11
<P>In a consolidated server system using virtualization, physical device accesses from guest virtual machines (VMs) need to be coordinated. In this environment, a separate driver VM is usually assigned to this task to enhance reliability and to reuse existing device drivers. This driver VM needs to be highly reliable, since it handles all the I/O requests. This paper describes a mechanism to detect and recover the driver VM from faults to enhance the reliability of the whole system. The proposed mechanism is transparent in that guest VMs cannot recognize the fault and the driver VM can recover and continue its I/O operations. Our mechanism provides a progress monitoring-based fault detection that is isolated from fault contamination with low monitoring overhead. When a fault occurs, the system recovers by switching the faulted driver VM to another one. The recovery is performed without service disconnection or data loss and with negligible delay by fully exploiting the I/O structure of the virtualized system.</P>
지상우,조환주,신희영,이상훈,안지환,Ji, Sangwoo,Jo, Hwanju,Shin, Hee-young,Lee, Sang-hun,Ahn, Ji-Whan 한국자원리싸이클링학회 2019 資源 리싸이클링 Vol.28 No.4
본 연구에서는 국내 폐광산에 이용될 채움재의 위해성 평가작업을 위한 전략과 방법론을 개념적 측면에서 제시하였다. 채움재는 석탄발전소 비산재와 고형재로 구성되어 있으며 탄산염 등 위해도가 적은 물질이 대부분을 차지하지만 일부 중금속 성분이 포함되어 있어서 이에 대한 위해성 평가가 요구된다. 위해성 평가는 주로 인체내 발암 및 비발암성 유발 가능성을 정량화하는 것이 목적이며, 본 연구의 경우 국내/외 토양 및 광해 위해성평가 기법을 참조 할 수 있을 것으로 판단된다. 이 때 독성이나 분배계수 등 항목별 주요 은 인자 값은 국내 토양위해성평가 가이드라인에서 제시하는 수치를 주로 이용할 수 있다. 오염도에 대한 정확한 위해 성평가는 현장답사와 실측 등을 통한 노력과 시간이 요구된다. 또한 채움재내 중금속 성분 및 농도가 매우 다양하고 반응이 복잡하여 이를 전부 상세하게 평가한다는 것은 비효율적이다. 따라서, 효과적인 위해성 평가를 위하여 일단 문헌 자료와 채움재 시료특성분석결과를 이용한 예비위해성평가를 먼저 실시하고, 그 이후 상세 위해성 평가에서 예비위해성평가에서 선정된 유의 사항을 중점적으로 다뤄야 할 것으로 생각된다. 이를 위해서는 신뢰성 있는 시료분석기법과 노출경로 및 관련 메커니즘에 대한 충분한 이해가 선행되어야 한다.
KAL: kernel-assisted non-invasive memory leak tolerance with a general-purpose memory allocator
Jeong, Jinkyu,Seo, Euiseong,Choi, Jeonghwan,Kim, Hwanju,Jo, Heeseung,Lee, Joonwon John Wiley Sons, Ltd. 2010 SOFTWARE-PRACTICE & EXPERIENCE Vol.40 No.8
<P>Memory leaks are a continuing problem in the software developed with programming languages, such as C and C++. A recent approach adopted by some researchers is to tolerate leaks in the software application and to reclaim the leaked memory by use of specially constructed memory allocation routines. However, such routines replace the usual general-purpose memory allocator and tend to be less efficient in speed and in memory utilization. We propose a new scheme which coexists with the existing memory allocation routines and which reclaims memory leaks. Our scheme identifies and reclaims leaked memory at the kernel level. There are some major advantages to our approach: (1) the application software does not need to be modified; (2) the application does not need to be suspended while leaked memory is reclaimed; (3) a remote host can be used to identify the leaked memory, thus minimizing impact on the application program's performance; and (4) our scheme does not degrade the service availability of the application while detecting and reclaiming memory leaks. We have implemented a prototype that works with the GNU C library and with the Linux kernel. Our prototype has been tested and evaluated with various real-world applications. Our results show that the computational overhead of our approach is around 2% of that incurred by the conventional memory allocator in terms of throughput and average response time. We also verified that the prototype successfully suppressed address space expansion caused by memory leaks when the applications are run on synthetic workloads. Copyright © 2010 John Wiley & Sons, Ltd.</P>