• KIISE Transactions on Computing Practices
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• v.23 no.7
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• pp.452-457
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• 2017

Linux is a general-purpose operating system that supports several schedulers, allowing different schedulers to coexist. In addition, Linux uses the Control Group (cgroup) to reserve CPU resources for task groups that follow the real-time (SCHED_FIFO, SCHED_RR) and non-real-time (SCHED_NORMAL) scheduler policies, except for the deadline scheduler (SCHED_DEADLINE). The cgroup performs the schedulability analysis to guarantee the reserved CPU resource as much as possible. However, current implementation of the schedulability analysis does not distinguish between deadline tasks and real-time tasks. Therefore, if these deadline tasks and real-time task groups coexist, there is a case where the resource reservation for the real-time task group is rejected. In this paper, we analyze the problems in the schedulability analysis for real-time task groups of Linux cgroups and propose patches to solve these problems.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.71-78
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• 2007

In this paper, an effective task scheduling scheme was proposed for the flexible real time LINUX systems with the selection between EDF(earliest deadline first) and RMS(rate monotonic scheduling). It was known that many task scheduling schemes were analyzed according to the characteristics of scheduling schemes and the guarantee of an earliest deadline scheduler for process utilities.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.40 no.5
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• pp.306-316
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• 2003

본 논문에서는 소프트웨어 PLC를 구현하는 방안을 제시하였다. 하드웨어는 표준적인 산업용 PC와 입출력 보드들로 구성된다. 운영체제로는 수십 마이크로초의 정밀한 단위로 태스크들의 스케줄링이 가능한 실시간 리눅스를 사용하였다. 소프트웨어 PLC를 위해 개발한 실시간 태스크들은 실시간 리눅스의 커널 모드에서 실행되며, 사용 목적에 따라 작성된 PLC 프로그램을 해석하고 실행하는 작업을 일정한 주기로 반복한다. 또한 PLC 프로그램을 편리하게 작성할 수 있도록 자체 프로그램 문법을 제안하고 이를 위한 컴파일러도 구현하였다. 이렇게 구현된 PLC는 가격 대비 성능이 우수하며 소규모의 응용분야들에 유용하게 활용할 수 있다.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.45-52
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• 2008

As multiple functions arc required in a robot controller, RTOS(Real Time Operating System) should be adopted to manage complex situations, such as choosing most urgent task among competing ones. In this paper, we implemented RTAI(Real Time Application Interface) based robot controller for wafer handling robots including graphic simulator. We showed how multiple tasks are organized and also explained in detail about task priorities and execution periods. Finally, we presented simulation results.

• The Journal of the Korea Contents Association
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• v.17 no.10
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• pp.587-597
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• 2017

Recently, the demand for real-time performance in mobile environment is increasing due to the improvement of hardware performance, however a GPOS(General-Purpose Operating System) such as Android and Linux do not provide real-time performance. We developed RTiK(Real-Time implant Kernel) for this problem, but it has the disadvantage of supporting only x86 Architecture. In this paper, we designed and implemented a RTiKA(Real-Time implanted Kernel for ARM) to support real-time in ARM Linux. We used MCT(Multi-Core Timer) timer which replaces Local APIC Timer for real-time support, and we measured the period of generated real-time task for performance verification and evaluation. As the recent the RTiKA can guarantee the operating of several real-time tasks based on the cycle of 1ms.

• The Journal of the Korea Contents Association
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• v.20 no.8
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• pp.54-64
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• 2020

RTiK-Linux is a method to provide real-time performance to Linux, it is controlled by directly accessing hardware registers to implement time tick interrupts. It implemented on x86 Intel and ARM based Exynoss 5422, but it had a disadvantage that it could not be ported to both fragmented other platform environments. In this paper, We change structure of time tick interrupt for improve po rtability so that it can operate on other platforms. We apply high-resolution timers that are independent of hardware, and modify operating structure to task and event to satisfy time determinism. It was confirmed that the improved RTiK-Linux works well in x86 and various ARM AP environments.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.337-342
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• 2012

This paper presents performance evaluation of real-time mechanisms for real-time embedded linux. First, we presents process for implementing open-source real-time embedded linux namely RTAI and Xenomai. These are real-time extensions to linux kernel and we implemented real-time embedded linux over the latest linux kernel. Measurements of executions of real-time mechanisms for each distribution are performed to give a quantitative comparison. Performance evaluations are conducted in kernel space about repeatability of periodic task, response time of Semaphore, FIFO, Mailbox and Message queue in terms of inter-task communication for each distribution. These rules can be helpful for deciding which real-time linux extension should be used with respect to the requirements of the real-time applications.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.15-16
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• 2009

OSEK/VDX 운영체제는 자동차 전자제어장치(ECU)를 위하여 OSEK/VDX에서 제안한 사양을 준수하는 실시간 운영체제이다. 본 연구는 OSEK/VDX 운영체제의 태스크관리 서비스들 중에서 태스크 활성화를 위한 서비스 함수를 설계하고 그 타당성을 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.1
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• pp.88-95
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• 2004

The previous disk scheduling schemes for best-effort applications do not guarantee the real-time requirement of multimedia objects and the real-time disk scheduling schemes do not satisfy throughput of multimedia server. So, this paper propose a two-step disk scheduling scheme to satisfy the requirement of best-effort as well as soft real-time applications. This scheme is based on the round robin algorithm that imposes different weights on the best-effort task and the real-time one. The experiment results on the Linux kernel have shown that both best-effort tasks and real-time tasks could get fair service.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.4
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• pp.201-212
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• 2002

This paper proposes a reconfigurable scheduler model that can support various real-time scheduling algorithms. The proposed model consists of two hierarchical upper and lower components, task scheduler and scheduling framework, respectively. The scheduling framework provides a job dispatcher and software timers. The task scheduler implements an appropriate scheduling algorithm, which supports a specific real-time application, based on the scheduling framework. If system developers observe internal kernel interfaces to communicate between two hierarchical components, they can implement a new scheduling algorithm independent of complex low kernel mechanism. Once a task scheduler is developed, it can be reused in a new real-time system in future. In Real-Time Linux (5), we implemented the proposed scheduling framework and several representative real-time scheduling algorithms. Throughout these implementations, we confirmed that a new scheduling algorithm could be developed independently without updates of complex low kernel modules. In order to confirm efficiency of the proposed model, we measured the performance of representative task schedulers. The results showed that the scheduling overhead of proposed model, which has two separated components, is similar to that of a classic monolithic kernel scheduler.