Incorporating Temporal Considerations during Assignment and Pre-run-time Scheduling of Objects and Processes
✍ Scribed by Jack P.C. Verhoosel; Lonnie R. Welch; Dieter K. Hammer; Erik J. Luit
- Book ID
- 102974749
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 517 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0743-7315
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✦ Synopsis
Given such a model, schedulability analysis techniques can be used to analyze an application [17]. Alternately, one can schedule a hard real-time system prerun-time, such that all timing constraints are satisfied and consistency of all resources, including processors, communication media, and devices, is guaranteed. With this approach, the run-time system simply dispatches and executes tasks according to the schedule constructed pre-runtime. Pre-run-time scheduling is the approach taken in this paper.
This paper considers a distributed memory MIMD system that consists of a set of homogeneous processors PR, a set of communication media CM, and a set of resources such as sensors and actuators. Each processor has a piece of private memory in which, usually part of, the application can be stored. A communication medium is assumed to be either a bus that typically connects a group of more than two processors or a high-speed bidirectional pointto-point link that connects only two processors directly. The only assumption that is made about the communication media interconnection topology among processors is that there is a unidirectional physical route from each processor to each other processor which consists of busses, links, and processors. Set RO is the set of all routes. Each resource is either a shared memory module or a physical device such as a sensor or an actuator. A shared memory module may be connected to a bus for temporary storage of global data. The module is then accessible by all processors connected to the bus. Each device has a bounded access time in order to be predictable. The device configuration is not fixed before an application is assigned to the system in order to reduce the constraints on the assignment. Only a maximum number of devices MDP can be assigned to each processor, due to physical constraints.
In order to guarantee timeliness, the complete system execution incorporating communication has to be scheduled pre-run-time such that consistency of all devices is guaranteed when the system operates according to the constructed schedule. Since the system operates strictly according to the pre-run-time schedule, no queues will exist at run-time. This means that a (local) schedule for each processor is constructed pre-run-time. This schedule indicates at which time a particular activity, which performs