• Journal of Korea Society of Industrial Information Systems
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• v.19 no.2
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• pp.15-22
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• 2014

This paper proposes a CUDA simulation framework for non-x86 computing platforms based on QEMU and GPGPU-sim. Previous simulators for heterogeneous computing platforms did not support for non-x86 CPU models or CUDA computing platform. In this work, we combined the QEMU and the GPGPU-Sim to support the non-x86 CPU models and the CUDA platform, respectively. This approach provides a simulation framework for CUDA computing on non-x86 CPU models.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.4-7
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• 2016

본 연구에서는 대표적인 오픈소스 virtual platform인 QEMU와 PC, FPGA에 다양한 운영체제(Windows, Linux, Android, ${\mu}C$/OS-II)를 포팅하고 벤치마크 프로그램을 수행함으로써 성능을 비교 분석하였다. 실험 결과 부동소수점 연산의 성능이 상대적으로 낮게 측정되었으며 이를 토대로 성능 취약점을 분석하고 QEMU를 개선하기 위한 방안을 연구하였다.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.105-113
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• 2011

During the development of flight software, the processor emulator and satellite simulator are essential tools for software development and verification, which can be substituted for the actual hardware. LEO satellites being developed by KARI recently use the MCM-ERC32SC processor for on-board computer (OBC). For the flight software (FSW) development and testing, the software-based spacecraft simulator was developed using TSIM-ERC32 processor emulator from Aeroflex Gaisler. It is needed to get rid of the constraints and dependencies of TSIM-ERC32 processor emulator and to obtain high performance processor emulator to develop full satellite simulator. This paper presents the development of the ERC32 emulator based on open source dynamic translator, QEMU, as the first step. And it describes the software development and testing/debugging on the developed emulator.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.76-78
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• 2015

시스템 자체를 에뮬레이션 하는 Virtual Platform은 임베디드 시스템 개발 프로세스 과정 중 하나인 소프트웨어 개발의 시점을 앞당길 수 있어 Time-To-Market을 줄일 수 있다. 본 논문에서는 Virtual Platform에 리눅스를 포팅하고 벤치마크 프로그램을 수행하여 성능을 측정하였다. 또한 이를 임베디드 시스템의 실제 개발단계에서 사용되는 Prototype Machine과 완성된 시제품에 각각 매칭 될 수 있는 FPGA 와 PC의 성능과 비교함으로써 Open Source Virtual Platform의 대표 주자인 QEMU의 효용성을 연구하였다. 실험 결과, 전체적인 성능은 PC가 FPGA보다 약 5.27배, FPGA가 Virtual Platform보다 5.38배, PC가 Virtual Platform보다 약 28.36배 더 좋은 성능을 보였다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.01a
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• pp.301-302
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• 2023

에뮬레이션 기술은 다양한 아키텍처에 대해 하드웨어 독립적인 실험 및 분석 환경을 제공하기 때문에 임베디드 기기 분석에 널리 활용되고 있다. 옥테온(Octeon) 아키텍처는 고성능 네트워크 장비에서 주로 사용되는 프로세서로, 이에 대응하는 에뮬레이션 환경의 구축이 어려워 초기 개발 및 분석에 어려움을 겪는다. 따라서 본 논문에서는 QEMU(v.6.0)을 활용한 옥테온 아키텍처의 에뮬레이션 환경을 구현하고 실험한 결과를 소개한다. 구현된 옥테온 에뮬레이션 환경은 옥테온 아키텍처 고유 인스트럭션 중 특정 하드웨어의 지원을 요하지 않는 인스트럭션에 대하여 에뮬레이션이 가능함을 보였으며 이는 옥테온 아키텍처 기반의 기기 프로그램 에뮬레이션에 활용할 수 있을 것으로 기대한다.

• Journal of KIISE
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• v.44 no.10
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• pp.1005-1018
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• 2017

Recently, virtualization has become an essential component of cloud computing due to its various strengths, including maximizing server resource utilization, easy-to-maintain software, and enhanced data protection. However, since virtualization allows sharing physical resources among the VMs, the system performance can be deteriorated due to device contentions. In this paper, we first investigate the I/O overhead based on the number of VMs on the same server platform and analyze the block I/O process of the KVM hypervisor. We also propose an in-memory block cache mechanism, called QBic, to overcome I/O virtualization latency. QBic is capable of monitoring the block I/O process of the hypervisor and stores the data with a high access frequency in the cache. As a result, QBic provides a fast response for VMs and reduces the I/O contention to physical devices. Finally, we present a performance measurement of QBic to verify its effectiveness.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.177-181
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• 2016

This paper analyzes the host cache effectiveness in full virtualization, particularly associated with journaling of guests. We observe that the journal access of guests degrades cache performance significantly due to the write-once access pattern and the frequent sync operations. To remedy this problem, we design and implement a novel caching policy, called PDC (Pollution Defensive Caching), that detects the journal accesses and prevents them from entering the host cache. The proposed PDC is implemented in QEMU-KVM 2.1 on Linux 4.14 and provides 3-32% performance improvement for various file and I/O benchmarks.

• KIISE Transactions on Computing Practices
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• v.24 no.3
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• pp.129-137
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• 2018

NVMe(Non-Volatile Memory Express) SSD(Solid State Drive) is a high-performance storage that makes use of flash memory as a storage cell, PCIe as an interface and NVMe as a protocol on the interface. It supports multiple I/O queues which makes it feasible to process parallel-I/Os on multi-core environments and to provide higher bandwidth than SATA SSDs. Hence, NVMe SSD is considered as a next generation-storage for data-center and cloud computing system. However, in the virtualization system, the performance of NVMe SSD is not fully utilized due to the bottleneck of the software I/O stack. Especially, when it uses I/O stack of the hypervisor or the host operating system like Xen and KVM, I/O performance degrades seriously due to doubled-I/O stack between host and virtual machine. In this paper, we propose a new I/O engine, called Direct-AIO (Direct-Asynchronous I/O) engine, that can access NVMe SSD directly for I/O performance improvements on QEMU emulator. We develop our proposed I/O engine and analyze I/O performance differences between the existed I/O engine and Direct-AIO engine.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5375-5400
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• 2016

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

• Journal of KIISE
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• v.42 no.12
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• pp.1480-1485
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• 2015

As SSDs are increasingly being used as high-performance storage or caches, attention is increasingly paid to the provision of SSDs with Quality-of-Service for I/O request streams of various applications in server systems. Since most SSDs are using the AHCI controller interface on a SATA bus, it is not possible to provide a differentiated service by distinguishing each I/O stream from others within the SSD. However, since a new SSD interface, the NVME controller interface on a PCI Express bus, has been proposed, it is now possible to recognize each I/O stream and schedule I/O requests within the SSD for differentiated services. This paper proposes Flash Operation Group Scheduling within NVME-based flash storage devices, and demonstrates through QEMU-based simulation that we can achieve a proportional bandwidth share for each I/O stream.