| 1. |
- Behnam, Moris, et al.
(författare)
-
A Hierarchical Approach for Reconfigurable and Adaptive Embedded Systems
- 2008
-
Ingår i: APRES'08 Adaptive and Reconfigurable Embedded Systems. ; , s. 51-54
-
Konferensbidrag (refereegranskat)abstract
- Adaptive and reconfigurable embedded systems have been gaining an increasing interest in the past year from both academics and industry. This paper presents our work on hierarchical scheduling frameworks (HSF) intended as a backbone architecture facilitating the implementation of operating system support for adaptability and reconfigurability.
|
|
| 2. |
|
|
| 3. |
- Behnam, Moris, et al.
(författare)
-
An overrun method to support composition of semi-independent real-time components
- 2008
-
Ingår i: Proceedings - International Computer Software and Applications Conference. - 9780769532622 ; , s. 1347-1352
-
Konferensbidrag (refereegranskat)abstract
- Engineers of embedded software systems rely on efficient design techniques and tools along with efficient run-time support. In the design of complex embedded real-time systems, the Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework enabling compositional schedulability analysis of embedded software systems with real-time properties. Moreover, the HSF provides a run-time framework guaranteeing that these non-functional requirements are met. In this paper a system consists of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF makes sure that the individual subsystems respect their allocated CPU budgets. However, as semi-independent sub-systems share logical resources, extra complexity is introduced. Specifically, the contribution of this paper is a novel method to allow for budget overruns; a common scenario when a subsystem utilizes shared logical resources. This proposed method is not only more resource efficient than existing methods, but it is also more appropriate for supporting composability of independently developed real-time subsystems.
|
|
| 4. |
- Behnam, Moris
(författare)
-
Hierarchical Real Time Scheduling and Synchronization
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation. In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism. In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness
|
|
| 5. |
- Behnam, Moris, et al.
(författare)
-
Improved SIRAP analysis for synchronization in hierarchical scheduled real-time systems
- 2009
-
Ingår i: Proceedings of 14th IEEE International Conference on Emerging Techonologies and Factory (ETFA'09). - 9781424427284
-
Konferensbidrag (refereegranskat)abstract
- We present our ongoing work on synchronization in hierarchical scheduled real-time systems, where tasks are scheduled using fixed-priority pre-emptive scheduling. In this paper, we show that the original local schedulability analysis of the synchronization protocol SIRAP is very pessimistic when tasks of a subsystem access many global shared resources. The analysis therefore suggests that a subsystem requires more CPU resources than necessary. A new way to perform the schedulability analysis is presented which can make the SIRAP protocol more efficient in terms of calculated CPU resource needs.
|
|
| 6. |
- Behnam, Moris, et al.
(författare)
-
Independent Abstraction and Dynamic Slack Reclaiming in Hierarchical Real-Time Open Systems
- 2007
-
Ingår i: Proceedings of the Work-In-Progress (WIP) session of the 19th Euromicro Conference on Real-Time Systems (ECRTS'07), Pisa, Italy. ; , s. 1-4
-
Konferensbidrag (refereegranskat)abstract
- Independent subsystem abstraction allows subsystems to be developed and validated separately and supports an easier subsystem integration. In particular, this approach is desirable in open systems, since it does not require knowledge of temporal behaviour of other subsystems. However, independentabstraction, assuming the worst-case CPU supply pattern, requires extra CPU allocations. We present our work in progress on dynamic slack reclamation, which keeps track of such extra CPU allocations at run time. We are also investigating how to utilize those extra resources for supporting soft real-time tasks.
|
|
| 7. |
|
|
| 8. |
- Behnam, Moris, et al.
(författare)
-
Overrun Methods for Semi-Independent Real-Time Hierarchical Scheduling
- 2009
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework to enable compositional schedulability analysis of embedded software systems with real-time properties. In this paper a software system consists of a number of semi-independent components called subsystems. Subsystems are developed independently and later integrated to form a system. To support this design process, in the paper, the proposed methods allow non-intrusive configuration and tuning of subsystem timing-behaviour via subsystem interfaces for selecting scheduling parameters. This paper considers three methods to handle overruns due to resource sharing between subsystems in the HSF. For each one of these three overrun methods corresponding scheduling algorithms The work in this paper is supported by the Swedish Foundation for Strategic Research (SSF), via the research programme PROGRESS. and associated schedulability analysis are presented together with analysis that shows under what circumstances one or the other is preferred. The analysis is generalized to allow for both Fixed Priority Scheduling (FPS) and Earliest Deadline First (EDF) scheduling. Also, a further contribution of the paper is the technique of calculating resource-holding times within the framework under different scheduling algorithms. The resource holding times being an important parameter in the global schedulability analysis.
|
|
| 9. |
- Behnam, Moris, et al.
(författare)
-
Real-Time Control and Scheduling Co-Design for Efficient Jitter Handling
- 2007
-
Ingår i: Proceedings - 13th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications. - 9780769529752 ; , s. 516-521
-
Konferensbidrag (refereegranskat)abstract
- Real-time control algorithms are designed based on thecharacteristics of the controlled plants and they require goodperformance without delays. However, digital control implementationtypically introduces delays and jitters due to insufficient CPUprocessing power and the limitations of the real-time schedulingmethod used. This can degrade the system performance or even make itunstable.In this paper we propose an integrated approach for control designand real-time scheduling, suitable for both discrete-time andcontinuous-time controllers. It guarantees system performance byaccepting a certain minimum value of jitter for control tasks andfeasibly schedules them together with other tasks in the system.Results from comparison with other approaches from real-time andcontrol theory domains underline the effectiveness of our method.
|
|
| 10. |
- Behnam, Moris, et al.
(författare)
-
Real-Time Control Design for Flexible Scheduling using Jitter Margin
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Real-time control algorithms are designed based on the characteristics of the controlled plants and they require good performance without delays. However, digital control implementation typically introduces delays and jitters due to insufficient CPU processing power and the limitations of the real-time scheduling method used. This can degrade the system performance or even make it unstable. In this paper we propose an integrated approach for control design and real-time scheduling, suitable for both discrete-time and continuous-time controllers. It guarantees system performance by accepting a certain minimum value of jitter for control tasks and feasibly schedules them together with other tasks in the system. Results from comparison with other approaches from real-time and control theory domains underline the effectiveness of our method.
|
|
