| 1. |
|
|
| 2. |
- Batsuuri, Tseesuren, et al.
(författare)
-
Performance and Fairness in VANETs
- 2011
-
Ingår i: Digest of Technical Papers - IEEE International Conference on Consumer Electronics. - 9781424487127 ; , s. 637-638
-
Konferensbidrag (refereegranskat)
|
|
| 3. |
|
|
| 4. |
- Bril, Reinder J., et al.
(författare)
-
Best-case response times and jitter analysis of real-time tasks with arbitrary deadlines
- 2013
-
Ingår i: RTNS '13 Proceedings of the 21st International conference on Real-Time Networks and Systems. - Sophia Antipolis, France : ACM. - 9781450320580 ; , s. 193-202
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present and prove exact best-case response time and improved jitter analysis of real-time periodic tasks with activation jitter and arbitrary deadlines that are scheduled by means of fixed-priority pre-emptive scheduling. We illustrate the analysis by means of examples.Apart from having a value on its own whenever timing constraints include lower bounds on response times of a system to events, our novel analysis also allows for an improvement of existing end-to-end response time analysis in distributed systems, i.e. where the finalization of one task on a processor activates another task on another processor.Best-case and worst-case analysis for tasks with constrained deadlines have a dual nature. We present various witnesses of non-duality of best-case and worst-case analysis for tasks with arbitrary deadlines, illustrating that both our novel best-case analysis and its proof are not straightforward extensions of existing work.
|
|
| 5. |
- Bril, Reinder J., et al.
(författare)
-
Generalized fixed-priority scheduling with limited preemptions
- 2012
-
Ingår i: Proceedings - Euromicro Conference on Real-Time Systems, 2012. - 9780769547398 ; , s. 209-220
-
Konferensbidrag (refereegranskat)abstract
- Fixed-priority scheduling with deferred preemption(FPDS) and fixed-priority scheduling with preemption thresholds(FPTS) have been proposed in the literature as viable alternatives to fixed-priority preemptive scheduling (FPPS), that reduce memory requirements, reduce the cost of arbitrary preemptions, and may improve the feasibility of a task set even when preemption overheads are neglected. This paper aims at advancing the relative strength of limited preemptive schedulers by combining FPDS and FPTS. In particular, we present a refinement of FPDS with preemption thresholds for both jobs and sub-jobs, termed FPGS. We provide an exact schedulability analysis for FPGS, and show how to maximize the feasibility of a set of sporadic tasks under FPGS for given priorities, computation times, periods, and deadlines of tasks. We evaluate the effectiveness of FPGS by comparing the feasibility of task sets under FPGS with other fixed-priority scheduling algorithms by means of a simulation. Our experiments show that FPGS allows an increase of the number of task sets that are schedulable under fixed-priority scheduling.
|
|
| 6. |
- Bril, Reinder J., et al.
(författare)
-
Improved feasibility of fixed-priority scheduling with deferred preemption using preemption thresholds for preemption points
- 2013
-
Ingår i: RTNS '13 Proceedings of the 21st International conference on Real-Time Networks and Systems. - New York, NY, USA : ACM. - 9781450320580 ; , s. 255-264
-
Konferensbidrag (refereegranskat)abstract
- This paper aims at advancing the relative strength of limited-preemptive schedulers by improving the feasibility of a task set and simultaneously limiting, or even precluding, arbitrary preemptions. In particular, we present a refinement of existing limited-preemptive fixed-priority scheduling (FPS) schemes with preemption thresholds for preemption points next to preemption thresholds for sub-jobs, termed fixed-priority scheduling with varying preemption thresholds (FPVS). We derive exact schedulability analysis for FPVS and we develop algorithms to maximize the schedulability of a set of sporadic tasks for given priorities. Since FPVS generalizes existing FPS schemes, we apply our algorithms to those schemes to compare the ratio of schedulable systems. Our experiments show that FPVS can achieve the same schedulability ratio with limited-preemptive sub-jobs as with entirely non-preemptive sub-jobs.
|
|
| 7. |
- Bril, Reinder J., et al.
(författare)
-
Worst-case response time analysis of real-time tasks under fixed-priority scheduling with deferred preemption
- 2009
-
Ingår i: Real-time systems. - Netherlands : Springer Science and Business Media LLC. - 0922-6443 .- 1573-1383. ; 42:1-3, s. 63-119
-
Tidskriftsartikel (refereegranskat)abstract
- Fixed-priority scheduling with deferred preemption (FPDS) has been proposed in the literature as a viable alternative to fixed-priority pre-emptive scheduling (FPPS), that obviates the need for non-trivial resource access protocols and reduces the cost of arbitrary preemptions. This paper shows that existing worst-case response time analysis of hard real-time tasks under FPDS, arbitrary phasing and relative deadlines at most equal to periods is pessimistic and/or optimistic. The same problem also arises for fixed-priority non-pre-emptive scheduling (FPNS), being a special case of FPDS. This paper provides a revised analysis, resolving the problems with the existing approaches. The analysis is based on known concepts of critical instant and busy period for FPPS. To accommodate for our scheduling model for FPDS, we need to slightly modify existing definitions of these concepts. The analysis assumes a continuous scheduling model, which is based on a partitioning of the timeline in a set of non-empty, right semi-open intervals. It is shown that the critical instant, longest busy period, and worst-case response time for a task are suprema rather than maxima for all tasks, except for the lowest priority task. Hence, that instant, period, and response time cannot be assumed for any task, except for the lowest priority task. Moreover, it is shown that the analysis is not uniform for all tasks, i.e. the analysis for the lowest priority task differs from the analysis of the other tasks. These anomalies for the lowest priority task are an immediate consequence of the fact that only the lowest priority task cannot be blocked. To build on earlier work, the worst-case response time analysis for FPDS is expressed in terms of known worst-case analysis results for FPPS. The paper includes pessimistic variants of the analysis, which are uniform for all tasks, illustrates the revised analysis for an advanced model for FPDS, where tasks are structured as flow graphs of subjobs rather than sequences, and shows that our analysis is sustainable.
|
|
| 8. |
- Cao, Jingyue, et al.
(författare)
-
An Independent yet Efficient Analysis of Bandwidth Reservation for Credit-based Shaping in Ethernet TSN
- 2018
-
Ingår i: International Workshop on Factory Communication Systems WFCS'18. - Imperia, Italy. - 9781538610664 ; , s. 1-10
-
Konferensbidrag (refereegranskat)abstract
- Ethernet TSN is an upcoming communication standard for industrial distributed embedded systems with high demands on bandwidth and traffic delay. In this paper, we present and prove an improved analysis to determine bandwidth reservations for credit based shapers in a single Ethernet TSN switch. We compare this new analysis, which is based on eligible intervals, to the state-of-the-art bandwidth reservation analysis based on busy periods through experiments. Despite its low complexity and the independence of the knowledge of the interfering traffic, the results show an improvement of efficiency, i.e., a decrease of the required bandwidth, for the new analysis.
|
|
| 9. |
- Holenderski, Mike J., et al.
(författare)
-
Grasp : Visualizing the Behavior of Hierarchical Multiprocessor Real-Time Systems
- 2013
-
Ingår i: Journal of systems architecture. - : Elsevier BV. - 1383-7621 .- 1873-6165. ; 59:6, s. 307-314
-
Tidskriftsartikel (refereegranskat)abstract
- Trace visualization is a viable approach for gaining insight into the behavior of complex distributed realtime systems. Grasp is a versatile trace visualization toolset. Its flexible plugin infrastructure allows for easy extension with custom visualization and analysis techniques for automatic trace verification. This paper presents its visualization capabilities for hierarchical multiprocessor systems, including partitioned and global multiprocessor scheduling with migrating tasks and jobs, communication between jobs via shared memory and message passing, and hierarchical scheduling in combination with multiprocessor scheduling. For tracing distributed systems with asynchronous local clocks Grasp also supports the synchronization of traces from different processors during the visualization and analysis.
|
|
| 10. |
- Holenderski, Mike J., et al.
(författare)
-
Memory Management for Multimedia Quality of Service in Resource Constrained Embedded Systems
- 2010
-
Ingår i: Proceedings of the 15th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2010. - 9781424468508
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider multimedia Quality-of-Service (QoS) in resource constrained embedded systems, where scalable applications are structured as directed acyclic graphs of tasks, which communicate via shared buffers. Scalable multimedia applications allow to trade quality for resource usage during run-time. We present two QoS problems: (i) temporal dependencies between subchains of tasks due to a common predecessor, and (ii) mode change latency in applications. These problems are addressed through advanced memory management techniques. For the first problem, it is shown how additional access to the buffer, in particular the support for dropping selected frames, allows to guarantee the Quality of Service of the application during overload conditions, preventing congestion in one buffer to propagate across the whole application. For the latter problem, the approach of in-buffer scaling is applied to reduce the mode change latency in scalable multimedia processing applications, which can adapt their memory requirements during runtime according to a set of predefined modes. The latter approach is validated with simulation results.
|
|
