Improved Scheduling of Control Tasks

The paper considers the implementation of digital controllers as real-time tasks in priority-preemptive systems. The performance of a digital feedback control system depends critically on the timing of its sampling and control actions. It is desirable to minimize the computational delay in the controller, as well as the sampling jitter and the control jitter. It is shown that by scheduling the two main parts of a control algorithm as separate tasks, the computational delay can often be reduced significantly. A heuristic method for assigning deadlines to the parts is presented. Further modifications are given to reduce the jitter and to facilitate delay compensation. The result is improved control performance under maintained schedulability

Feedback and time are essential for the optimal control of computing systems

The performance, reliability, cost, size and energy usage of computing systems can be improved by one or more orders of magnitude by the systematic use of modern control and optimization methods. Computing systems rely on the use of feedback algorithms to schedule tasks, data and resources, but the models that are used to design these algorithms are validated using open-loop metrics. By using closed-loop metrics instead, such as the gap metric developed in the control community, it should be possible to develop improved scheduling algorithms and computing systems that have not been over-engineered. Furthermore, scheduling problems are most naturally formulated as constraint satisfaction or mathematical optimization problems, but these are seldom implemented using state of the art numerical methods, nor do they explicitly take into account the fact that the scheduling problem itself takes time to solve. This paper makes the case that recent results in real-time model predictive control, where optimization problems are solved in order to control a process that evolves in time, are likely to form the basis of scheduling algorithms of the future. We therefore outline some of the research problems and opportunities that could arise by explicitly considering feedback and time when designing optimal scheduling algorithms for computing systems

Timing analysis for embedded systems using non-preemptive EDF scheduling under bounded error arrivals

Embedded systems consist of one or more processing units which are completely encapsulated by the devices under their control, and they often have stringent timing constraints associated with their functional specification. Previous research has considered the performance of different types of task scheduling algorithm and developed associated timing analysis techniques for such systems. Although preemptive scheduling techniques have traditionally been favored, rapid increases in processor speeds combined with improved insights into the behavior of non-preemptive scheduling techniques have seen an increased interest in their use for real-time applications such as multimedia, automation and control. However when non-preemptive scheduling techniques are employed there is a potential lack of error confinement should any timing errors occur in individual software tasks. In this paper, the focus is upon adding fault tolerance in systems using non-preemptive deadline-driven scheduling. Schedulability conditions are derived for fault-tolerant periodic and sporadic task sets experiencing bounded error arrivals under non-preemptive deadline scheduling. A timing analysis algorithm is presented based upon these conditions and its run-time properties are studied. Computational experiments show it to be highly efficient in terms of run-time complexity and competitive ratio when compared to previous approaches

APLIKASI PENYUSUNAN JADWAL MATA KULIAH DAN RUANGAN DI FAKULTAS ILMU KOMPUTER DENGAN PEMROGRAMAN BERORIENTASI OBJEK

Scheduling is an important process in project management that involves setting time, resources, and tasks to be completed. The purpose of setting a schedule is to organize and coordinate activities so as to achieve project goals efficiently. In the process of preparing a schedule, steps such as assistance with tasks, time estimates, setting priorities, allocating resources, and setting the sequence of activities carried out. The main components of a schedule include assignment of tasks to individuals or teams, costing start and finish times for each task, assistance of dependencies between tasks, and visualization of the schedule in graphical or tabular form. The benefits of effective scheduling include improved team coordination, monitoring of project progress , time control, risk and schedule conflict assistance, and the ability to make more accurate plans. However, the schedule development process also faces challenges, such as limited resources, tension in time estimates, and unexpected changes. Therefore, schedule flexibility and adaptation to changing conditions are important considerations in preparing the schedule. In this abstract, we provide an overview of the process and purpose of developing a schedule. It is hoped that this brief explanation will provide readers with an initial understanding of how important scheduling is in project management and how it can help achieve goals efficiently

Scheduling Algorithm for Real-Time Embedded Control Systems using Arduino Board

The time taken for the scheduling task in a control system to reduce the traffic within the system is one of significant field of research in modern era. There are different control systems that require time scheduling such as elevator control system, traffic control system and train control system. Currently, there are unique control logic strategies adopting scheduling algorithm that are implemented in real time systems like earliest deadline first and ant colony optimization. At the same time, the disadvantages possessed by them are the exponential dip in the performance ratio due to over loading. Despite of all the available resources there are many issues faced such as congestion in traffic networks due to non-adaptive scheduling algorithms, etc., which led to several misfortunes and danger for human life. Hence an improved algorithm that increases the efficiency of the system is required to validate the processing time and the deadlines. Our research is focused on validating a proposed idea of using Arduino microcontroller to implement the different scheduling tasks and validate the efficiency of the algorithm to optimize the results of the system. This take cares of assigning the critical paths which priorities the tasks and focuses on reducing the scheduling time. This rapidly increases the processing speed and efficiency of the algorithm. We plan to use the Arduino board which has an inbuilt error detection algorithm that helps in checking whether the time scheduling is done effectively. In the initial phase of the project we develop and fabricate the hardware design using CAD design software packages like Solid Works. This is later employed with suitable environmental interfaces like, sensors and microcontrollers that can work in an adaptable environment as per requirements to validate the scheduling algorithm. The scheduling algorithm can also be used for controlling the current flow and power storage which will contribute a lot in the power consumption aspect. Graphical data interpretation of various algorithms from the past literature is observed and few selected ones are to be implemented in the experimental set up that is built as an initial proof of concept. By analyzing the results from the simulations carried out using the Altera FPGA board with VHDL and Arduino it is clear that we obtain better results using the Arduino board. Finally, to have an extensive study on different intelligent control logics that are used in the above mentioned control systems, we use the prototyped miniature model of an elevator system and a train control system to validate the different disk scheduling approaches like First Come-First Serve (FCFS), Elevator (SCAN) and ant colonization to solve the discrete combinational optimization of the scheduling logic. Initial validation of the system focuses on the effectiveness of using the ant colonization strategies to enhances the efficiency of the scheduling algorithm and optimize it for real time application

PAStime: Progress-Aware Scheduling for Time-Critical Computing

Over-estimation of worst-case execution times (WCETs) of real-time tasks leads to poor resource utilization. In a mixed-criticality system (MCS), the over-provisioning of CPU time to accommodate the WCETs of highly critical tasks may lead to degraded service for less critical tasks. In this paper we present PAStime, a novel approach to monitor and adapt the runtime progress of highly time-critical applications, to allow for improved service to lower criticality tasks. In PAStime, CPU time is allocated to time-critical tasks according to the delays they experience as they progress through their control flow graphs. This ensures that as much time as possible is made available to improve the Quality-of-Service of less critical tasks, while high-criticality tasks are compensated after their delays. This paper describes the integration of PAStime with Adaptive Mixed-criticality (AMC) scheduling. The LO-mode budget of a high-criticality task is adjusted according to the delay observed at execution checkpoints. This is the first implementation of AMC in the scheduling framework of LITMUS^RT, which is extended with our PAStime runtime policy and tested with real-time Linux applications such as object classification and detection. We observe in our experimental evaluation that AMC-PAStime significantly improves the utilization of the low-criticality tasks while guaranteeing service to high-criticality tasks

Real-time scheduling algorithms, task visualization

Real-time systems are computer systems that require responses to events within specified time limits or constraints. Many real-time systems are digital control systems comprised entirely of binary logic or a microprocessor dedicated to one software application that is its own operating system. In recent years, the reliability of general-purpose real-time operating systems (RTOS) consisting of a scheduler and system resource management have improved. In this project, I write a real-time simulator, a workload generator, analysis tools, several test cases, and run and interpret results. My experiments focus on providing evidence to support the claim that for the Rate Monotonic scheduling algorithm (RM), workloads with harmonically non-similar, periodic tasks are more difficult to schedule. The analysis tool I have developed is a measurement system and real-time simulator that analyzes real-time scheduling strategies. I have also developed a visualization system to display the scheduling decisions of a real-time scheduler. Using the measurement and visualization systems, I investigate scheduling algorithms for real-time schedulers and compare their performance. I run different workloads to test the scheduling algorithms and analyze what types of workload characteristics are preferred for real-time benchmarks

Scheduling of Early Quantum Tasks

An Early Quantum Task (EQT) is a Quantum EDF task that has shrunk its first period into one quantum time slot. Its purpose is to be executed as soon as possible, without causing deadline overflow of other tasks. We will derive the conditions under which an EQT can be admitted and can have an immediate start. The advantage of scheduling EQTs is shown by its use in a buffered multi-media server. The EQT is associated with a multimedia stream and it will use its first invocation to fill the buffer, such that a client can start receiving data immediately