• 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.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.202-204
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• 2003

경성 실시간 시스템(Hard Real-Time System)어서는 주기 태스크들의 엄격한 마감시간(Deadline) 보장이 시스템의 성능을 좌우한다. 본 논문에서는 CPU의 이용률(Utilization)이 높아 비율단조 정책으로는 마감시간을 보장 할 수 없는 주기 태스크들을 위해 확장된 스케줄 가능성 검사를 통해 수행할 태스크들의 공통 주기(L.C.M : Least Common Multiple)내에서 EDF(Earliest-Deadline First) 정책을 기반으로 마감시간 보장 수행패턴(Feasible Pattern)을 찾고, 이를 참조하여 우선순위를 고려하지 않고 태스크들을 강제 수행할 수 있게 하는 비율단조 기반의 스케쥴링 기법을 제안한다. EDF를 기반으로 생성된 패턴은 EDF 정책의 특성에 따라 CPU의 이용률을 100% 까지 가능하게 하며 패턴을 참조하여 강제 수행함으로써 EDF 정책이 갖는 실행시간 스케쥴링 오버헤드를 없앨 수 있다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2
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• pp.507-519
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• 2000

n this paper, we implement the real-time scheduler which performs extended schedulability testing, to reconfigure Mach kernel in which Real-Time scheduling is possible. for this purpose, first, we propose the configuration factors according to requirements of Real-Time operation systems and we analyze a Real-time scheduling algorithm. Second, for the reconfiguration of Mach kernel, we propose the modified data structure through the analysis of Mach kernel environments and scheduling. Third, we suggest the extended scheduling method by analyzing conventional Real-Time scheduling policies. Fourth, we implement the scheduler which executes tasks according to the Earliest-Deadline-First scheduling and the Rate Monotonic scheduling.

• Journal of Internet Computing and Services
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• v.6 no.2
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• pp.25-35
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• 2005

The Rate Monotonic(RM) scheduling algorithm and Earliest Deadline First(EDF) scheduling algorithm are normally used in Real-Time scheduling algorithm. In those scheduling algorithm, we could predict the performance possibility with total utilization value of task group. But. it had problems with prediction of the boundedness in individual task when the utilization value was over in temporary task. In this paper, the suggested scheduling algorithm can predict task when the utilization value was over and it suggested the method of predicting scheduling possibility based on the utilization value of individual task as well. it predicted the boundedness of scheduling possibility test through simulation In Real-Time scheduling algorithm and analyzed the result.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.50-60
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• 2004

Recently, most of the embedded system is required not only many functions but also real-time characteristics in purpose. In the hard real-time system, especially, strict deadline of periodic task can affect the performance of the system. In this paper, we design and implement the scheduler based on RM(Rate-Monotonic) rule. This scheduler makes feasible patterns based on EDF(Earliest deadline first) rule with extended schedulability inspection before execution, for periodic task-set that has high CPU utilization and then, execute periodic task-set depended on feasible patterns. The feasible pattern formed into EDF rule is capable of the efficiency of CPU up to 100 percentage and by the referenced execution of the feasible pattern is possible of removing the red-time scheduling overhead that is the defect of the order of dynamic assignment rule.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1613-1616
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• 2010

본 논문은 실시간 운영체제인 Xenomai 를 사용하여, 회전익 무인항공기 소프트웨어 개발에 대한 내용을 설명하고 있다. 실시간 운영체제 사용하여 고정 순위 우선 스케줄링을 채택함으로써 데드라인의 타이밍(Timming) 결정성을 보장하였고, 이기종 시스템과의 호환성과 확장성을 고려하여 POSIX API 를 사용하여 멀티 쓰레드를 구현하였다. 또한 실시간 드라이버 모델(RTDM : Real-Time Driver Model)을 사용하여 획득한 데이터를 실시간 전송이 가능하도록 하였다. 본 논문은 실시간 운영체제를 무인항공기에 적용하고 구현된 비행제어 컴퓨터와 제어 소프트웨어를 비율 단조 스케줄링을 적용하여 무인항공기의 쓰레드들의 응답 속도 및 안정성을 보장하는 방안을 제시하였다.

• Journal of KIISE
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• v.44 no.2
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• pp.115-123
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• 2017

A message processor is server software that receives non-realtime messages as well as realtime messages from clients that need to be processed within a deadline. With the recent advances of micro-processor technologies and Linux, the message processor is often implemented in Linux-based multi-core servers and it is important to use cores efficiently to maximize the performance of system in multi-core environments. Numerous research efforts on a real-time scheduler for the efficient utilization of the multi-core environments have been conducted. Typically, though, they have been conducted theoretically or via simulation, making a subsequent real-system application difficult. Moreover, many Linux-based real-time schedulers can only be used in a specific Linux version, or the Linux source code needs to be modified. This paper presents the design of a Linux-based message processor for multi-core environments that maps the threads to the cores at user level. The message processor is implemented through a modification of the traditional RM algorithm that consolidates the real-time messages into certain cores using a first-fit-based bin-packing algorithm; this minimizes the response-time delay of the non-real-time messages, while guaranteeing the violation rate of the real-time messages. To compare the performances, the message processor was implemented using the two multi-core-scheduling algorithms GSN-EDF and P-FP, which are provided by the LITMUS framework. The benchmarking results show that the response-time delay of non-real-time messages in the proposed system was improved up to a maximum of 17% to 18%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2891-2898
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• 2014

It is feasible to develop a fault tolerant system through module level redundancy on the Integrated Modular Avionics (IMA). However, its great implementation complexity is one of important challenges when asynchronous hardware environment is naturally assumed. To solve this problem, Physically Asynchronous Logically Synchronous (PALS) on IMA has been proposed. But, it has adaptation problem by not addressing specific architecture for IMA system. In the paper, we propose how to synchronize the input data on the IMA system under primary/secondary redundancy architecture by referring to existing PALS. In the proposed scheme, we introduce window frame by considering rate monotonic scheduling and analyze the adequate the synchronization time. Finally, we verify the feasibility of the proposed design pattern through the systematic experiments.