Object-based programming techniques help to reduce the cost of software development and maintenance due to the benefits of reuse, information hiding, and encapsulation. This is especially helpful in ...large, real-time systems that are highly parallel and distributed. The paper reviews asemi-preemptionexecution model of object-based real-time systems that simplifies reasoning about the quality of process-to-processor assignment. The model is used to define system properties such as interprocess parallelism, processor utilization, and interprocessor communication. Additionally, an innovative assignment algorithm is presented which incorporates feasibility constraints. The algorithm is guided by an objective that balances minimum communication against maximum parallelism. Experimental results show that the process assignment algorithm performs extremely well with respect to finding process assignments in isolation. The algorithm easily finds process assignments for which a feasible schedule exists as long as the number of items to be scheduled does not exceed approximately 500.
Dedos: a distributed real-time environment Hammer, D.K.; Luit, E.J.; van Roosmalen, O.S. ...
IEEE parallel & distributed technology,
1994, Letnik:
2, Številka:
4
Journal Article
Until now, little research has been done on methods to combine the seemingly incompatible paradigms of hard and soft real-time systems. To this end, we have developed Dedos, a dependable distributed ...operating system. The driving forces behind the project are twofold: to meet the demand for dependable distributed control systems, especially in the area of embedded systems and industrial control; and to increase the productivity and quality of application programming for distributed control. Our current focus is on hard real-time issues; soft real-time needs are handled by conventional techniques. However, our work has raised interesting questions about the communication between the soft and hard real-time tasks of the system, which is necessary to pass externally specified control parameters and control status information. The problem is that the data set must always be consistent (concurrency atomicity), but hard real-time activities can never be delayed by soft real-time ones. Other intriguing questions are related to the integration of the reliability and security concepts that are used in the two parts of the systems. in this paper, however, we limit our discussion to the Dedos development model, the Dedos programming model, hard real-time scheduling, and the distributed algorithms needed to implement the Dedos execution environment.< >
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