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Hyunchan Park
Division of Computer Science and Engineering, Jeonbuk National University, Jeonju 54896, Korea

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Journal article
Published: 29 July 2020 in Applied Sciences
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In cloud systems, computing resources, such as the CPU, memory, network, and storage devices, are virtualized and shared by multiple users. In recent decades, methods to virtualize these resources efficiently have been intensively studied. Nevertheless, the current virtualization techniques cannot achieve effective I/O virtualization when packets are transferred between a virtual machine and a host system. For example, VirtIO, which is a network device driver for KVM-based virtualization, adopts an interrupt-based packet-delivery mechanism, and incurs frequent switch overheads between the virtual machine and the host system. Therefore, VirtIO wastes valuable CPU resources and decreases network performance. To address this limitation, this paper proposes an adaptive polling-based network I/O processing technique, called NetAP, for virtualized environments. NetAP processes network requests via a periodical polling-based mechanism. For this purpose, NetAP adopts the golden-section search algorithm to determine the near-optimal polling interval for various workloads with different characteristics. We implement NetAP in a Linux kernel and evaluated it with up to six virtual machines. The evaluation results show that NetAP can improve the network performance of virtual machines by up to 31.16%, while only using 32.92% of the host CPU time used by VirtIO for packet processing.

ACS Style

Hyunchan Park; Juyong Seong; Munkyu Lee; Kyungwoon Lee; Cheol-Ho Hong. NetAP: Adaptive Polling Technique for Network Packet Processing in Virtualized Environments. Applied Sciences 2020, 10, 5219 .

AMA Style

Hyunchan Park, Juyong Seong, Munkyu Lee, Kyungwoon Lee, Cheol-Ho Hong. NetAP: Adaptive Polling Technique for Network Packet Processing in Virtualized Environments. Applied Sciences. 2020; 10 (15):5219.

Chicago/Turabian Style

Hyunchan Park; Juyong Seong; Munkyu Lee; Kyungwoon Lee; Cheol-Ho Hong. 2020. "NetAP: Adaptive Polling Technique for Network Packet Processing in Virtualized Environments." Applied Sciences 10, no. 15: 5219.

Research article
Published: 18 June 2020 in Computer Applications in Engineering Education
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Assignments on kernel programming are essential parts of operating system (OS) courses taught to computer science students to provide them a deep understanding of real‐world OSs. However, these assignments require tremendous effort from both students and instructors. Students are routinely flustered by the daunting task of building a practice environment from scratch; instructors are pressurized for time while validating a student's work that requires several kernel installations and reboots. To minimize this effort, we propose CLIK, a cloud‐based Linux kernel practice environment supporting automatic judgment. It provides students with an individual and easy‐to‐use kernel practice environment and instructors with a fast and easy evaluation of students' work with live feedback. Our experiences with two assignments from a real‐world OS course carried out on CLIK show that CLIK can successfully provide Linux kernel environments for 40 students and help instructors greatly by validating their kernels within one minute using parallel and automated judgments. We also describe detailed lessons learned from developing CLIK that will help both researchers and instructors building similar systems.

ACS Style

Hyunchan Park; Youngpil Kim. CLIK: Cloud‐based Linux kernel practice environment and judgment system. Computer Applications in Engineering Education 2020, 28, 1137 -1153.

AMA Style

Hyunchan Park, Youngpil Kim. CLIK: Cloud‐based Linux kernel practice environment and judgment system. Computer Applications in Engineering Education. 2020; 28 (5):1137-1153.

Chicago/Turabian Style

Hyunchan Park; Youngpil Kim. 2020. "CLIK: Cloud‐based Linux kernel practice environment and judgment system." Computer Applications in Engineering Education 28, no. 5: 1137-1153.

Journal article
Published: 23 March 2020 in IEEE Access
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The problem associated with current file archiving systems is a slow processing time owing to unnecessary data copying. To address this problem, a novel archiving system with zero-copy merging and splitting operations, referred to as AvaTar, is presented herein. For the operations, instead of copying the data, the block allocation information of the files is manipulated at the kernel level. We implemented kernel-level archiving primitives in a Linux kernel, called AvaTar-FS, and a user-level archiving tool, called AvaTar agent. Our evaluation results indicated that AvaTar required only 0.48 s to extract 1,024 files from a 4 GB archive file, which is 132-times faster when compared with traditional GNU Tar archiving. AvaTar affords practical benefits in uploading files to a real-world cloud storage system, and successfully completes the transfer of 1,024 files to Amazon Web Service cloud storage within 60.55% of the processing time required through a traditional approach.

ACS Style

Hyunchan Park; Youngpil Kim; Seehwan Yoo. AvaTar: Zero-Copy Archiving With New Kernel-Level Operations. IEEE Access 2020, 8, 59315 -59325.

AMA Style

Hyunchan Park, Youngpil Kim, Seehwan Yoo. AvaTar: Zero-Copy Archiving With New Kernel-Level Operations. IEEE Access. 2020; 8 (99):59315-59325.

Chicago/Turabian Style

Hyunchan Park; Youngpil Kim; Seehwan Yoo. 2020. "AvaTar: Zero-Copy Archiving With New Kernel-Level Operations." IEEE Access 8, no. 99: 59315-59325.

Journal article
Published: 04 February 2020 in Applied Sciences
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In cloud computing, a shared storage server, which provides a network-attached storage device, is usually used for centralized data management. However, when multiple virtual machines (VMs) concurrently access the storage server through the network, the performance of each VM may decrease due to limited bandwidth. To address this issue, a flash-based storage device such as a solid state drive (SSD) is often employed as a cache in the host server. This host-side flash cache saves remote data, which are frequently accessed by the VM, locally in the cache. However, frequent VM migration in the data center can weaken the effectiveness of a host-side flash cache as the migrated VM needs to warm up its flash cache again on the destination machine. This study proposes Cachemior, Firepan, and FirepanIF for rapid flash-cache migration in cloud computing. Cachemior warms up the flash cache with a data preloading approach using the shared storage server after VM migration. However, it does not achieve a satisfactory level of performance. Firepan and FirepanIF use the source node’s flash cache as the data source for flash cache warm-up. They can migrate the flash-cache more quickly than conventional methods as they can avoid storage and network congestion on the shared storage server. Firepan incurs downtime of the VM during flash cache migration for data consistency. FirepanIF minimizes the VM downtime with the invalidation filter, which traces the I/O activity of the migrated VM during flash cache migration in order to invalidate inconsistent cache blocks. We implement and evaluate the three flash cache migration techniques in a realistic virtualized environment. FirepanIF demonstrates that it can improve the performance of the I/O workload by up to 21.87% compared to conventional methods.

ACS Style

Hyunchan Park; Munkyu Lee; Cheol-Ho Hong. FirepanIF: High Performance Host-Side Flash Cache Warm-Up Method in Cloud Computing. Applied Sciences 2020, 10, 1014 .

AMA Style

Hyunchan Park, Munkyu Lee, Cheol-Ho Hong. FirepanIF: High Performance Host-Side Flash Cache Warm-Up Method in Cloud Computing. Applied Sciences. 2020; 10 (3):1014.

Chicago/Turabian Style

Hyunchan Park; Munkyu Lee; Cheol-Ho Hong. 2020. "FirepanIF: High Performance Host-Side Flash Cache Warm-Up Method in Cloud Computing." Applied Sciences 10, no. 3: 1014.

Research article
Published: 20 September 2018 in Scientific Programming
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Solid-state drive (SSD) becomes popular as the main storage device. However, over time, the reliability of SSD degrades due to bit errors, which poses a serious issue. The periodic remapping (PR) has been suggested to overcome the issue, but it still has a critical weakness as PR increases lifetime loss. Therefore, we propose the conditional remapping invocation method (CRIM) to sustain reliability without lifetime loss. CRIM uses a probability-based threshold to determine the condition of invoking remapping operation. We evaluate the effectiveness of CRIM using the real workload trace data. In our experiments, we show that CRIM can extend a lifetime of SSD more than PR by up to 12.6% to 17.9% of 5-year warranty time. In addition, we show that CRIM can reduce the bit error probability of SSD by up to 73 times in terms of typical bit error rate in comparison with PR.

ACS Style

Youngpil Kim; Hyunchan Park; Cheol-Ho Hong; Chuck Yoo. CRIM: Conditional Remapping to Improve the Reliability of Solid-State Drives with Minimizing Lifetime Loss. Scientific Programming 2018, 2018, 1 -10.

AMA Style

Youngpil Kim, Hyunchan Park, Cheol-Ho Hong, Chuck Yoo. CRIM: Conditional Remapping to Improve the Reliability of Solid-State Drives with Minimizing Lifetime Loss. Scientific Programming. 2018; 2018 ():1-10.

Chicago/Turabian Style

Youngpil Kim; Hyunchan Park; Cheol-Ho Hong; Chuck Yoo. 2018. "CRIM: Conditional Remapping to Improve the Reliability of Solid-State Drives with Minimizing Lifetime Loss." Scientific Programming 2018, no. : 1-10.

Journal article
Published: 01 November 2014 in Journal of Systems and Software
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ACS Style

Hyunchan Park; Sam H. Noh; Chuck Yoo. O1FS: Flash file system with O(1) crash recovery time. Journal of Systems and Software 2014, 97, 86 -96.

AMA Style

Hyunchan Park, Sam H. Noh, Chuck Yoo. O1FS: Flash file system with O(1) crash recovery time. Journal of Systems and Software. 2014; 97 ():86-96.

Chicago/Turabian Style

Hyunchan Park; Sam H. Noh; Chuck Yoo. 2014. "O1FS: Flash file system with O(1) crash recovery time." Journal of Systems and Software 97, no. : 86-96.