Fohler, G. (1994). Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Institut fur Technische Informatik, Treitlstr. Vienna, Austria.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....available in the interval [a; d) is e; if the job is admitted, then the available idle times are appropriately decremented. This approach has since been significantly extended to more general job, task, and system models, notably in the slot shifting work of Fohler and colleagues (see, e.g. [3]) This research. The preprocessing phase of the Chetto Chetto algorithm requires the sequential consideration of a time interval of length proportional to the least common multiple of the periods of the periodic tasks (see [2] for details) and is hence an inherently exponential time ....

....of periodic hard real time tasks, such that the feasibility of none of the periodic jobs or previously admitted aperiodic jobs is compromised. One approach towards solving this problem was pioneered by Chetto Chetto [2] this approach has subsequently been extended by Fohler and colleagues [3]) The Chetto Chetto approach (and hence by extension, the work of Fohler et al. suffers from the drawback that it requires exponential time preprocessing of the system of periodic tasks, in order to compute certain data structures that are necessary for performing on line admission control. ....

G. Fohler. Flexibility in Statically-Scheduled Hard-RealTime Systems. PhD thesis, Technische Universitat Wien, 1994.

....available in the interval ### ## is # #; if the job is admitted, then the available idle times are appropriately decremented. This approach has since been significantly extended to more general job, task, and system models, notably in the slot shifting work of Fohler and colleagues (see, e.g. [4]) This research. The preprocessing phase of the Chetto Chetto algorithm requires the sequential consideration of a time interval of length proportional to the least common multiple of the periods of the periodic tasks (see [3] for details) and is hence an inherently exponential time ....

....of periodic hard real time tasks, such that the feasibility of none of the periodic jobs or previously admitted aperiodic jobs is compromised. One approach towards solving this problem was pioneered by Chetto Chetto [3] this approach has subsequently been extended by Fohler and colleagues [4]) The Chetto Chetto approach (and hence by extension, the work of Fohler et al. suffers from the drawback that it requires exponential time preprocessing of the system of periodic tasks, in order to compute certain data structures that are necessary for performing on line admission control. ....

G. Fohler. Flexibility in Statically-Scheduled Hard-RealTime Systems. PhD thesis, Technische Universitat Wien, 1994.

....it handles (somewhat) different requirements. It does not, as [13] and [35] assume that all nodes in the system are identical; it does not as [30] require software circuits to be statically allocated to nodes; it does not as most algorithms assume that communication takes zero time; it does not as [10] assume that the ticklength is the same for all nodes in the system. Furthermore, our algorithm does not use heuristic search methods to find a schedule, instead it uses (heuristic) estimations and decisions that (seem to) make the backtracking unnecessary. One benefit of this is that the ....

Gerhard Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technischen Universitat Wien Austria, 1994.

....I also contacted Christer Eriksson at the Department of Real time Computer Systems, M alardalen University, V aster as. He has develped an off line scheduler that takes mode shift, interrupt and communication between red and blue processes into consideration [EL94a] In the MARS project (see [Foh94] there is a static scheduling algorithm developed that takes dynamic changes into consideration using mode shift (changing schedule) Within the VIA project there is also work done under Roger Johansson at Chalmers in G oteborg but their work concentrate mostly on fault tolerance. I have also ....

....statically assigned to nodes before the scheduling starts (e.g. SG91] This is not the case in the used algorithm. ffl Communication takes zero time, no algorithms care about communication times. This is not the case in BASEMENT. ffl The ticklength is the same for all nodes in the system (e.g. Foh94] The tool must handle different ticklengths. The used algorithm basically consists of two parts: 1. Node allocation and relation selection VIA BASEMENT RTS: The Scheduling Tool, ProVIA 94204, Version 0 Draft, January 25, 1995 12 2. Communication initiation The scheduling algorithm doesn t ....

Gerhard Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technischen Universit at Wien Austria, 1994.

....search algorithms to find the feasible task sequence. Good examples of state of the art scheduling algorithms can be the branch and bound algorithm by Xu and Parnas [10] where tasks with exclusive relations and precedence constraints are scheduled in a preemptive manner and the Mars scheduler [5] using an iterative deepening search algorithm to solve the distributed scheduling problem. If we tried to use a traditional search based solution of this kind, we should use a fairly complex heuristic function to achieve the secondary goal of minimizing the jitter. The problem of finding a ....

G. Fohler, "Flexibility in Statically Scheduled Hard Real-Time Systems," Technisch Naturwissenschaftliche Fakultaet, Technische Universitaet Wien, April 1994.

....(somewhat) different requirements. It does not, as [HAR94] and [Xu93] assume that all nodes in the system are identical; it does not as [SG91] require software circuits to be statically allocated to nodes; it does not as most algorithms assume that communication takes zero time; it does not as [Foh94] assume that the tick length is the same for all nodes in the system. Furthermore, our algorithm does not use heuristic search methods to find a schedule, instead it uses (heuristic) estimations and decisions that (seem to) make the backtracking unnecessary. One benefit of this is that the ....

Gerhard Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technischen Universitat Wien Austria, 1994.

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G. Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

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G. Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....end to end deadlines in distributed systems, completed by constraints from experienced engineers such as separation of messages on the bus to reduce EMI risks, allocation of tasks to nodes, etc. A number of algorithms for the construction of offline schedules has been presented, e.g. 7] [2] to address the NP hard problem in a heuristic, efficient way. These algorithms focus, however, on providing one shot single solutions, i.e. constructing a schedule for a specified application. Changes in the created schedule or the specification are not supported or require rescheduling ....

G. Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....3.1 Local scheduling algorithm We use the slotshifting method to schedule the tasks on locally on each node. Foh95] 1 . Due to space limitations, we cannot give a full description here, but con ne to salient features relevant to our new algorithms. More detailed descriptions can be found in [Foh94], IF99] It uses standard o ine schedulers, e.g. Ram90] Foh94] to create schedules which are then analyzed to de ne start times and deadlines of tasks, and these tasks can then be scheduled by EDF at runtime. The resulting feasible schedules represent the original complex constraints. ....

....schedule the tasks on locally on each node. Foh95] 1 . Due to space limitations, we cannot give a full description here, but con ne to salient features relevant to our new algorithms. More detailed descriptions can be found in [Foh94] IF99] It uses standard o ine schedulers, e.g. Ram90] [Foh94] to create schedules which are then analyzed to de ne start times and deadlines of tasks, and these tasks can then be scheduled by EDF at runtime. The resulting feasible schedules represent the original complex constraints. Additional runtime tasks, however, can create overload situations, ....

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G. Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....overall constraints, e.g. demanded by control performance. Instead of specific requirements, our algorithm takes an entire off line schedule and all task requirements to determine task attributes. A method to transform off line schedules into earliest deadline first tasks has been presented in [5]. A related paper [4] deals with priority assignment for off line schedules. It uses a constructive, heuristic approach, potentially creating large numbers of artifacts, while the approach presented here generates optimal solutions with an ILP based algorithm. The paper is organized as follows: ....

G. Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....constraints, e.g. demanded by control performance. Instead of specific requirements, our algorithm takes an entire off line schedule and all message requirements to determine message attributes. A method to transform off line schedules into earliest deadline first tasks has been presented in [4]. A related paper [3] deals with priority assignment for off line CPU scheduled tasks. It uses a constructive, heuristic approach, potentially creating large numbers of artifacts, while the approach presented here presents a general algorithm applied to message scheduling on CAN using ILP for ....

G. Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....propose to use the offline transformation and online guarantee of complex constraints of the slot shifting method [8] 1 . Due to space limitations, we cannot give a full description here, but confine to salient features relevant to our new algorithms. More detailed descriptions can be found in [7], 8] 12] It uses standard offline schedulers, e.g. 20] 7] to create schedules which are then analyzed to define starttimes and deadlines of tasks. First, the offline scheduler creates scheduling tables for the selected periodic tasks with complex constraints. It allocates tasks to nodes ....

....of complex constraints of the slot shifting method [8] 1 . Due to space limitations, we cannot give a full description here, but confine to salient features relevant to our new algorithms. More detailed descriptions can be found in [7] 8] 12] It uses standard offline schedulers, e.g. 20] [7] to create schedules which are then analyzed to define starttimes and deadlines of tasks. First, the offline scheduler creates scheduling tables for the selected periodic tasks with complex constraints. It allocates tasks to nodes and resolves complex constraints by constructing sequences of task ....

[Article contains additional citation context not shown here]

G. Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....a overall constraints, e.g. demanded by control performance. Instead of specific requirements, our algorithm takes an entire off line schedule and all task requirements to determine task attributes. A method to transform offline schedules into earliest deadline first tasks has been presented in [3]. A related paper [2] deals with priority assignment for offline schedules, but using only a constructive, heuristic approach, potentially creating large numbers of artifacts tasks. 2 Algorithm Figure 1 gives an overview of the algorithm. 2.1 Overview 1) Initially, tasks are given with their ....

....priorities, offsets, periods, deadlines, it is straightforward to schedule these using FPS. Off line schedule: First, an off line schedule is created for a set of tasks and constraints. While our method does not rely on a particular off line scheduling algorithm, we have used the one described in [3] for our implementation and analysis. The schedule is usually created up to the least common multiple, LCM , of all task periods. LCM=T (T i ) instances of each task T i with period T (T i ) will execute in the schedule. The off line scheduler resolves constraints such as distribution, end to end ....

G. Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

....If the sum of all three is larger than MAXT (TA ) TA can be accommodated, and therefore guaranteed. Upon guarantee of a task, the spare capacities are updated to reflect the decrease in available resources. This guarantee algorithm is O(N) N being the number of intervals. It is shown in [7], that this acceptance test has equivalent results but with simpler run time handling as to the ones presented in [9] and [6] which are optimal for single processors. On line scheduling On line scheduling is performed locally for each node. If the spare capacities of the current interval ....

G. Fohler. Flexibility in Statically Scheduled Hard RealTime Systems. PhD thesis, Technische Universitat Wien, Austria, Apr. 1994.

No context found.

Fohler, G. (1994). Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universitat Wien, Institut fur Technische Informatik, Treitlstr. Vienna, Austria.

No context found.

G. Fohler. Flexibility in Statically Scheduled Hard Real-Time Systems. PhD thesis, Technische Universit at Wien, Austria, Apr. 1994.

No context found.

G. Fohler, "Flexibility in Statically Scheduled Hard Real-Time Systems," PhD thesis, Technishe Universitt Wien, 1994.

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