• ETRI Journal
• /
• v.14 no.1
• /
• pp.23-39
• /
• 1992

본 논문에서는 기존의 정적인 스케쥴링 모델 즉, 그래프 이론, 정수 프로그래밍 그리고 휴리스틱 모델에 근거한 알고리즘들의 사례를 소개하고 분석하였으며 정적인 스케쥴링 알고리즘의 단점을 보완할 수 있고 고장허용구조를 지원할 수 있는 FAME 알고리즘을 제시하였다. FAME은 정적인 휴리스틱 알고리즘과 동적인 스케쥴링 알고리즘으로 구성되며 부하균형과 기억공간 크기 그리고 최소 통신비용 조건을 만족하고 태스크간 간섭비용을 도입함으로써 태스크간 통신 비용에 의해 나타날 수 있는 태스크들의 동시성 수행 정도의 감소를 방지할 수 있도록 하였다. 또한 기억공간 크기와 간섭비용의 조합은 테스크들이 일부 프로세서에만 할당되는 현상을 방지할 수 있다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2000.04a
• /
• pp.89-91
• /
• 2000

멀티미디어 응용이 점점 널리 사용되면서 멀티미디어 응용에 적합한 태스크 모델의 연구가 진행되었으나, 기존의 태스크 모델은 멀티미디어 응용의 특성을 충분히 반영하지 못하였다. 본 논문에서는 멀티미디어 응용의 자원 사용량의 패턴에 기반한 확률적 멀티프레임 태스크 모델(PMF)을 제시하고, PMF를 멀티미디어 응용의 스케줄링에 적용하여 CPU 자원을 효율적으로 이용하면서 멀티미디어 응용에게 통계적 QoS를 제공할 수 있는 방안을 제시한다. 또한, 다양한 스케줄링 기법을 채용한 모의실험을 통해 제시한 태스크 모델이 자원을 최대한 활용 하면서 응용에게 QoS를 보장할 수 있음을 보인다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04a
• /
• pp.97-99
• /
• 2003

대칭형 다중프로세서 (SMP: Symmetric Multiprocessors) 시스템은 고성능의 병렬 연산을 위한 중요하고 효과적인 기반환경을 제공하고 있다. SMP에서 태스크 클러스터링과 스케줄링 기법은 시스템의 성능에 큰 영향을 미친다. 본 논문에서는 버스 기반의 SMP에서 사용할 수 있는 태스크 중복 기반의 클러스터링과 스케줄링 기법을 소개한다. 본 논문에서 제안한 클러스터링 기법에서는 휴리스틱을 사용하여 중복할 태스크를 선택한 후 프로세서에 할당하고, 스케줄링 기법에서는 잠재하는 통신 충돌을 방지하기 위하여 네트워크 통신 자원을 사전에 할당한다. 새로운 클러스터링과 스케줄링 기법의 성능을 확인하기 위하여 시뮬레이션에서는 통신비용의 변화에 대한 병렬연산시간을 비교하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.8B
• /
• pp.509-520
• /
• 2007

In this paper, we propose a real-time sensor node platform that guarantees the real-time scheduling of periodic and aperiodic tasks through a multitask-based software decomposition technique. Since existing sensor networking operation systems available in literature are not capable of supporting the real-time scheduling of periodic and aperiodic tasks, the preemption of aperiodic task with high priority can block periodic tasks, and so periodic tasks are likely to miss their deadlines. This paper presents a comprehensive evaluation of how to structure periodic or aperiodic task decomposition in real-time sensor-networking platforms as regard to guaranteeing the deadlines of all the periodic tasks and aiming to providing aperiodic tasks with average good response time. A case study based on real system experiments is conducted to illustrate the application and efficiency of the multitask-based dynamic component execution environment in the sensor node equipped with a low-power 8-bit microcontroller, an IEEE802.15.4 compliant 2.4GHz RF transceiver, and several sensors. It shows that our periodic and aperiodic task decomposition technique yields efficient performance in terms of three significant, objective goals: deadline miss ratio of periodic tasks, average response time of aperiodic tasks, and processor utilization of periodic and aperiodic tasks.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.1
• /
• pp.97-102
• /
• 2014

Abdelzaher et al. proposed an algorithm to determine the schedulability of aperiodic tasks on multiprocessor systems, and proved that the aperiodic tasks are schedulable if the upperbound of synthetic utilization is less than or equal to 0.59. But this algorithm has a drawback in that if some tasks, even though they are completed and have no more execution times, are included in the current invocation set, their execution times and deadlines are added to the synthetic utilization. This may lead to a problem in which actually schedulable tasks are decided not to be schedulable. In this paper, we recognize the above mentioned problem and propose an improved synthetic utilization method that can be used to schedule aperiodic tasks more efficiently on multiprocessor systems.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.11
• /
• pp.1333-1343
• /
• 1999

경성 실시간 시스템의 태스크들은 논리적으로 올바른 결과를 산출해야 하지만 또한 각자의 시간 제한 조건을 만족하여야 한다. 간격제한 스케줄링은 시간 제한 조건이 시간 간격 제한으로 주어지는 실시간 태스크들을 스케줄하기 위하여 도입되었다. 간격제한 스케줄링에서의 각 태스크들은 시간 간격 제한 조건을 갖는데, 이것은 태스크의 두 연속적인 수행의 종료시간에 대해 제한을 가한다. 다시 말해, 간격제한 스케줄링에서의 각 태스크 수행은 그 태스크의 직전 수행 완료 시간으로부터 발생하는 데드라인을 갖는다. 간격제한 태스크 스케줄링에 관한 많은 연구는 단순화 방법에 기초하고 있다. 그러나, 우리는 이 논문에서 단순화 방법을 사용하지 않고, 정적 우선순위 및 정적 분리 제한 정책을 채용한 새로운 간격제한 태스크 스케줄링 방법을 제안한다. 제안된 정적 할당 방법은 스케줄링 분석 및 구현을 매우 간단히 할 수 있으며, 또한 스케줄러의 실행시간 오버헤드를 줄일 수 있다.Abstract Tasks in hard real-time systems must not only be logically correct but also meet their timing constraints. The distance-constrained scheduling has been introduced to schedule real-time tasks whose timing constraints are characterized by temporal distance constraints. Each task in the distance-constrained scheduling has a temporal distance constraint which imposes restriction on the finishing times of two consecutive executions of the task. Thus, each execution of a task in the distance-constrained scheduling has a deadline relative to the finishing time of the previous execution of the task.Much work on the distance-constrained task scheduling has been based on the reduction technique. In this paper, we propose a new scheme for the distance-constrained task scheduling which does not use the reduction technique but adopts static priority and static separation constraint assignment policy. We show that our static assignment approach can simplify the scheduling analysis and its implementation, and can also reduce the run-time overhead of the scheduler.

• Journal of the Korea Society of Computer and Information
• /
• v.16 no.2
• /
• pp.193-199
• /
• 2011

In this paper, we proposed battery driven low power algorithm in mobile device. Algorithm the mobile devices in power of the battery for the task to perform power consumption to reduce the frequency alters. Power of the battery perform to a task power consumption of is less than the task perform to frequency the lower. Frequency control the task, depending on in the entire system devices used among the highest frequency with devices first target perform to. Frequency in the decrease the second largest frequency with of the device the frequency in changes the power consumption to calculate. The calculated consumption power the battery of level is greater than level the frequency by adjusting power consumption, lower power of the battery the task perform when you can to the frequency to adjust. Experiment the frequency by adjusting power consumption a method to reduce using [6] and in the same environment power of the battery consider the task to perform frequency were controlled. The results in [6] perform does not battery power on task operates that the result was.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.7
• /
• pp.22-28
• /
• 2009

As multiprocessors have been widely adopted in embedded systems, task computation energy consumption should be minimized with several low power techniques supported by the multiprocessors. This paper proposes an energy-aware task scheduling algorithm that adopts both dynamic voltage scaling and power shutdown in multiprocessor environments. Considering the timing and energy overhead of power shutdown, the proposed algorithm performs an iterative task assignment and task ordering for multiprocessor systems. In this case, the iterative priority-based task scheduling is adopted to obtain the best solution with the minimized total energy consumption. Total energy consumption is calculated by considering a linear programming model and threshold time of power shutdown. By analyzing experimental results for standard task graphs based on real applications, the resource and timing limitations were analyzed to maximize energy savings. Considering the experimental results, the proposed energy-aware task scheduling provided meaningful performance enhancements over the existing priority-based task scheduling approaches.

• Journal of Digital Contents Society
• /
• v.9 no.3
• /
• pp.441-448
• /
• 2008

Recently, several algorithms for scheduling aperiodic tasks have been proposed. Among them, Abdelzaher et al proposed an algorithm to determine the schedulability of aperiodic tasks, and proved that the aperiodic tasks are schedulable if the upperbound of synthetic utilization is less than or equal to $\frac 1{1+\sqrt{1/2}}{\approx}0.59$. But this algorithm has a drawback in that if some tasks, even though they are completed and have no more execution times, are included in the current invocation set, their execution times and deadlines are added to the synthetic utilization. This may lead to a problem in which actually schedulable tasks are decided not to be schedulable. In this paper, we recognize the above mentioned problem and propose an improved synthetic utilization method that can be used to schedule aperiodic tasks more efficiently.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.2
• /
• pp.261-274
• /
• 1999

Recently, automated business processing systems, so called workflow systems, have been studied. have been studied. even though each task has noticible duration inherently, most of previous models regard it as a simple finite automation where state transitions occur instantly. In this paper, we propose a modeling method for workflow each of whose component task has minimum processing time and due-date. Firstly we provide a priority function to choose the proper alternatives when tasks fail before their due-date. The priority function considers the time-relevant factor and the semantic compatibility level to decide the best alternative. secondly, we identify six different types of execution requirements for tasks with noticible durations. They are serial, parallel, simultaneous start simultaneous termination, interleaved and nested dependency. Note that previous models deal with only serial execution and parallel execution. Lastly, we also propose graph-based methods to detect logical conflicts in time constraint-based workflow specifications.