• The Transactions of the Korea Information Processing Society
• /
• v.2 no.1
• /
• pp.119-129
• /
• 1995

In this paper, we propose a schedulatility analysis method for real-time programs. Several approaches to anlayzing schedulability have been developed, but since these approaches use a fixed priority scheduling method and/or traverse all possible state spaces, there take place exponential time and space complexity of these methods, Therefore it is necessary to reduce the state space and detect schedulability at earlier time. Our schedulability analysis method uses a minimum unit time taken to terminate synchronization action, a minimum unit time taken to terminate actions after synchronization, and a deadline of processes to detect unschedulability at earlier time and dynamic scheduling scheme to reduce state space. We conclude that our method can detected unschedulability earlier 50 percent unit time than Fredette's method.

• Journal of the Korea Computer Industry Society
• /
• v.2 no.7
• /
• pp.923-932
• /
• 2001

In this paper, An imprecise real-time task sets composed of multimedia datas are generated using several parameters and an algorithm which can analyse schedulability of generated imprecise real-time task sets before execution of this task sets is proposed. Also, The schedulability of task set depends on variation of parameter values which were used during the generation of the task set is studied. As a result of experiment, It isproved that the schedulability of task set is more and more weak as large as execution requirement time of mandatory subtasks and, as many as the number of tasks which can be scheduled at some instant. The schedulabilty analysis algorithm which is presented on this paper is expected to use effectively on QoS service of multimedia datas.

• KIISE Transactions on Computing Practices
• /
• v.23 no.7
• /
• pp.452-457
• /
• 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 KIISE:Computer Systems and Theory
• /
• v.28 no.11
• /
• pp.573-580
• /
• 2001

When tasks access shared resources in real-time systems, the unbounded priority inversion may occur. In such cases it is impossible to guarantee the schedulability of real-time tasks. Several resource access protocols have been proposed to bound the duration of priority inversion and sufficient conditions are given to guarantee the schedulability of periodic task set. In this paper, we show an improved sufficient condition for schedulability when the dynamic priority ceiling protocol is used. Our approach exploits the fact that a lower priority task can continue to execute as far as the higher priority tasks do not miss their deadlines. This permitting execution time of the higher priority tasks for a lower priority task can be excluded from the worst-case blocking time of the higher priority tasks. Since the worst-case blocking time of tasks can be reduced, the sufficient condition for schedulability of dynamic priority ceiling protocol becomes further tight.

• Journal of the Korea Convergence Society
• /
• v.12 no.2
• /
• pp.15-20
• /
• 2021

The imprecise real-time scheduling can be used for minimizing the bad effects of timing faults by leaving less important tasks unfinished if necessary when a transient overload occured. In the imprecise scheduling, every time-critical task can be logically decomposed into two tasks : a mandatory task and an optional task. Recently, some studies in this field showed good schedulability performance and minimum total error by deferring the optional tasks. But the schedulability performance of the studies can be shown only when the execution time of each optional task was less than or equal to the execution time of its corresponding mandatory task. Therefore, in this paper, a new deferring strategy is proposed under the reverse execution time restriction to the previous studies. Nevertheless, the strategy produces comparable or superior schedulability performance to the previous studies and can minimize the total error also.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.10
• /
• pp.2797-2808
• /
• 1999

Timing Constraint Petri Nets(TCPN) extend petri nets by adding timing constraints, it is provide a formal method for the modeling and analysis of real-time system. A real-time schedulability analysis decide that a set of concurrent processes will always meet its deadline. In this paper, we present TCPN model for real-time system include timing constraints and propose a schedulability analysis algorithm using them. Also, When the TCPN model is unscheduleable under the imposed timing constraints, we propose a recovery technique that will be scheduleable by the system specification modifying or timing constraints relaxing in the optimized time.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.12
• /
• pp.1338-1345
• /
• 2014

Recently, wireless technology gains attention for industrial networks due to low cost, flexibility, relatively easy installation and most importantly, solving the rouring issue. ISA100.11a is one of promising standard for wireless industrial networks (WINs). Data traffic in industrial networks are known to be periodic and must satisfy the real-time property namely deadline. Therefore, in this paper, we proposed to apply deadline monotonic scheduling to periodic tasks in ISA100.11a networks and to evaluate the performance of ISA100.11a by checking the schedulability and beacon frame overhead. Simulation results showns, that our proposed scheme can reduces the network overhead while maintaining schedulability as compared to the previous algorithm. In addition, by reducing the network overhead, our proposed scheme can send more data without degrading the overall performance of WINs.

• Journal of KIISE:Computer Systems and Theory
• /
• v.29 no.9
• /
• pp.520-529
• /
• 2002

This paper presents an approach for scheduling network messages with real-time dynamic algorithms. We present the method that calculates an intermediate relative deadline of the message based on the EDF(Earliest Deadline First) scheduling policy. We adjust the slack of message by using this intermediate relative deadline to allocate a priority of message. The priority of the message can be determined accurately by using the slack that calculates in our approach, which increases the schedulability efficiency of the message. As a result, we reduce the worst-case response time and improve the guarantee ratio of real-time messages. Also, we describe the analysis method to check the schedulability on message sets, and show the efficiency of our approach by comparing the results of the DM(Deadline Monotonic) approach and the existing EDF approach with that of the improved EDF in our approach through the simulation.

• KIISE Transactions on Computing Practices
• /
• v.21 no.9
• /
• pp.604-609
• /
• 2015

The use of Operating System(OS) virtualization is increasing as it provides many useful features such as efficient use of hardware(HW), easy system migration, and isolation between virtual spaces which prevents errors effecting each other. Recent development in HW has made it possible to use OS virtualization in embedded systems. However, implementing OS virtualization means that a multiple number of schedulers are layered in a system, rendering it difficult to analyze the schedulability of the system and errors are easily produced. Errors in safety critical embedded systems can cause serious damage to life and property; thus, the hierarchical schedulability must be verified. In this paper, we propose a framework which supports formal modeling and verification of hierarchical scheduling systems with UPPAAL.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.1
• /
• pp.194-203
• /
• 2005

The process of guaranteeing that a distributed real-time control system will meet its timing constraints, is referred to as schedulability analysis. However, schedulability analysis algorithm cannot be simply used to analyze the system because of complex calculations of algorithm. It is difficult for control engineer to understand the algorithm because it was developed in a software engineer's position. In this paper we introduce a Response-time Analysis Tool(RAT) which provides easy way far system designer to analyze the system by encapsulating calculation complexity. Based on the RAT, control engineer can verify whether all real-time tasks and messages in a system will be completed by their deadline in the system design phase.