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| 2. |
- Bril, Reinder J., et al.
(författare)
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Worst-case response time analysis of real-time tasks under fixed-priority scheduling with deferred preemption
- 2009
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Ingår i: Real-time systems. - Netherlands : Springer Science and Business Media LLC. - 0922-6443 .- 1573-1383. ; 42:1-3, s. 63-119
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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.
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| 3. |
- Cao, Jingyue, et al.
(författare)
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An Independent yet Efficient Analysis of Bandwidth Reservation for Credit-based Shaping in Ethernet TSN
- 2018
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Ingår i: International Workshop on Factory Communication Systems WFCS'18. - Imperia, Italy. - 9781538610664 ; , s. 1-10
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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.
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| 4. |
- Holenderski, Mike J., et al.
(författare)
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Grasp : Visualizing the Behavior of Hierarchical Multiprocessor Real-Time Systems
- 2013
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Ingår i: Journal of systems architecture. - : Elsevier BV. - 1383-7621 .- 1873-6165. ; 59:6, s. 307-314
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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.
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| 5. |
- Holenderski, Mike J., et al.
(författare)
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Memory Management for Multimedia Quality of Service in Resource Constrained Embedded Systems
- 2010
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Ingår i: Proceedings of the 15th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2010. - 9781424468508
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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.
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| 6. |
- Holenderski, Mike J., et al.
(författare)
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Parallel-task scheduling on multiple resources
- 2012
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Ingår i: Proceedings - Euromicro Conference on Real-Time Systems, 2012. - 9780769547398 ; , s. 233-244
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of scheduling periodic parallel tasks on a multi-resource platform, where tasks have real-time constraints. The goal is to exploit the inherent parallelism of a platform comprised of multiple heterogeneous resources. A resource model is proposed, which abstracts the key properties of any heterogeneous resource from a scheduling perspective. A new scheduling algorithm called PSRP is presented, which refines MSRP. The schedulability analysis for PSRP is presented. The benefits of PSRP are demonstrated by means of an example application showing that PSRP indeed exploits the available concurrency in heterogeneous real-time systems.
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| 7. |
- Holenderski, Mike J., et al.
(författare)
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Reducing memory requirements in a multimedia streaming application
- 2011
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Ingår i: Digest of Technical Papers - IEEE International Conference on Consumer Electronics, 2011. - 9781424487127 ; , s. 325-326
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Konferensbidrag (refereegranskat)abstract
- This paper investigates memory management for real-time multimedia applications running on a resource-constrained platform. It is shown how a shared memory pool can reduce the total memory requirements of an application comprised of a data-driven chain of tasks with a time-driven head and tail and a bounded end-to-end latency. The general technique targeted at memory-constrained streaming systems is demonstrated with a video encoding example, showing memory savings of about 19%.
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| 8. |
- Holenderski, Mike J., et al.
(författare)
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Reducing memory requirements in a multimedia streaming application
- 2011
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Ingår i: IEEE transactions on consumer electronics. - Las Vegas, United States. - 0098-3063 .- 1558-4127. ; 57:1, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates memory management for real-time multimedia applications running on resource-constrained electronic devices. The target applications are comprised of a data-driven task chain with a time-driven head and tail and a bounded end-to-end latency. The necessary buffer capacities along the task chain are derived. Subsequently it is shown how a shared memory pool can reduce the total memory requirements of the whole application. The impact of a shared memory pool is also evaluated in the context of scalable applications. The general technique targeted at memory-constrained streaming systems is demonstrated with a video encoding example, showing memory savings of about 19%.
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| 9. |
- Holenderski, Mike J., et al.
(författare)
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Swift mode changes in memory constrained real-time systems
- 2009
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Konferensbidrag (refereegranskat)abstract
- A method for "preempting memory" is presented, where (parts of) the memory allocated to an active task may be reallocated to another task, without corrupting the state of the active task's job. The method is based on combining scalable components with Fixed-Priority Scheduling with Deferred Preemption (FPDS). Real-time systems composed of scalable components are investigated. A scalable component can operate in one of several modes, where each mode defines a certain trade off between the resource requirements and output quality. The focus of this paper is on memory constrained systems, with modes limited to memory requirements. During runtime the system may decide to reallocate the resources between the components, resulting in a mode change. The latency of a mode change should satisfy timing constraints expressed by upper bounds. A modeling framework is presented combining scalable components with FPDS. A quantitive analysis comparing Fixed-Priority Preemptive Scheduling (FPPS) and FPDS is provided, showing that FPDS sets a lower bound on the mode change latency. The analytical results are verified by simulation. The results for both FPPS and FPDS are applied to improve the existing latency bound for mode changes in the processor domain. The presented protocol is especially suited for pipelined applications, allowing to perform the mode change without the need to first clear the whole pipeline.
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| 10. |
- J. Bril, Reinder, et al.
(författare)
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Cost of Robustness of independent WCRT analysis for CBS of Ethernet AVB using eligible intervals
- 2023
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Ingår i: 2023 IEEE 19TH INTERNATIONAL CONFERENCE ON FACTORY COMMUNICATION SYSTEMS, WFCS. - : IEEE. - 9781665464321 ; , s. 229-232
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Konferensbidrag (refereegranskat)abstract
- The existing worst-case response time (WCRT) analysis for individual priority classes under credit-based shaping (CBS) in Ethernet AVB based on so-called eligible intervals is both independent and tight. This WCRT analysis does not rely on any assumptions on interfering inter-priority streams other than those enforced by the Ethernet standard. A major advantage of this independent analysis is that CBS may be viewed as resource reservation, where allocated bandwidth is both guaranteed and enforced. Although independent analysis provides inter-priority class robustness, it comes at a cost of over-provisioning bandwidth. We illustrate this cost of inter-priority class robustness by means of an example that requires 7.8 times the amount of bandwidth reservation for a given set of streams compared to a different analysis that takes knowledge of interpriority streams into account.
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