| 21. |
- Becker, Matthias, et al.
(författare)
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Increased Reliability of Many-Core Platforms through Thermal Feedback Control
- 2014
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Ingår i: Performance, Power and Predictability of Many-Core Embedded Systems 3PMCES'14. - Dresden, Germany.
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Konferensbidrag (refereegranskat)abstract
- In this paper we present a low overhead thermal management approach to increase reliability of many-core embedded real-time systems. Each core is controlled by a feedback controller. We adapt the utilization of the core in order to decrease the dynamic power consumption and thus the corresponding heat development. Sophisticated control mechanisms allow us to migrate the load in advance, before reaching critical temperature values and thus we can migrate in a safe way with a guarantee to meet all deadlines.
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| 22. |
- Becker, Matthias, et al.
(författare)
-
Limiting temperature gradients on many-cores by adaptive reallocation of real-time workloads
- 2014
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Ingår i: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014. - 9781479948468 ; , s. Article number 7005241-
-
Konferensbidrag (refereegranskat)abstract
- The advent of many-core processors came with the increase in computational power needed for future applications. However new challenges arrived at the same time, especially for the real-time community. Each core on such a processor is a heat source and uneven usage can lead to hot spots on the processor, affecting its lifetime and reliability. For real-time systems, it is therefore of paramount importance to keep the temperature differences between the individual cores below critical values, in order to prevent premature failure of the system. We argue that this problem can not be solved by traditional approaches, since the growing number of cores makes them intractable. We rather argue to split the problem in the spacial domain and control the temperature on core level. The cores control their temperature by rearranging the load in a predictable manner during runtime. To achieve this, a feedback controller is implemented on each core. We conclude our work with a simulation based evaluation of the proposed approach comparing its performance against a previously presented algorithm.
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| 23. |
- Becker, Matthias, et al.
(författare)
-
Mapping Real-Time Tasks onto Many-Core Systems considering Message Flows
- 2014
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Ingår i: Proceedings of the Work-in-Progress Session of the 20th IEEE Real-Time and Embedded Technology and Applications Symposium. - Berlin, Germany. ; , s. 17-18
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Konferensbidrag (refereegranskat)abstract
- In this work we focus on the task mapping problem for many-core real-time systems. The growing number of cores connected by a Network-on-Chip (NoC) calls for sophisticated mapping techniques to meet the growing demands of real-time applications. Hardware should be used in an efficient way such that unnecessary resource usage is avoided. Because of the NP-hardness of the problem, heuristic and meta-heuristic techniques are used to find good solutions. We further consider periodic communication between tasks and we focus on a static mapping solution.
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| 24. |
- Behnam, Moris, et al.
(författare)
-
Analysis and Optimization of the MTU in Real-Time Communications over Switched Ethernet
- 2011
-
Ingår i: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA. ; , s. Art.nr. 6059021-
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Konferensbidrag (refereegranskat)abstract
- The Flexible Time-Triggered communication over Switched Ethernet protocol (FTT-SE) was proposed to overcome the limitation of guaranteeing the real-time communication requirements of conventional switches, and at the same time to support reconfiguration of dynamic adaptive systems. The protocol fragments large messages into a sequence of packets that are individually scheduled. The maximum transmission unit (MTU), that restricts the packets size, has a significant effect on the schedulability of the packets. In this paper, we investigate the problem of selecting the optimal MTU size that maximizes the schedulability of real-time messages. We propose two algorithms to find optimal/sub-optimal values of MTU; the first one finds an optimal solution but exhibits high computational complexity, while the second one is sub-optimal but exhibits a lower computational complexity. Finally, we evaluate our proposed algorithms by means of simulation studies and compare their results with the results of assigning MTU to the maximum packet size that the protocol can allow.
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| 25. |
- Behnam, Moris, 1973-, et al.
(författare)
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Bounding the number of self-blocking occurrences of SIRAP
- 2010
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Ingår i: Proceedings - Real-Time Systems Symposium. - 9780769542980 ; , s. 61-72
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a new schedulability analysis for hierarchically scheduled real-time systems executing on a single processor using SIRAP; a synchronization protocol for inter subsystem task synchronization. We show that it is possible to bound the number of self-blocking occurrences that should be taken into consideration in the schedulability analysis of subsystems. Correspondingly, we present two novel schedulability analysis approaches with proof of correctness for SIRAP. An evaluation suggests that this new schedulability analysis can decrease the analytical subsystem utilization significantly
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| 26. |
- Behnam, Moris, et al.
(författare)
-
Engineering and analyzing multi-switch networks with single point of control
- 2011
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Ingår i: 1st International Workshop on Worst-Case Traversal Time, WCTT 2011, Held in Conjunction with the 32nd IEEE Real-Time Systems Symposium, RTSS 2011; Vienna; 29 November 2011 through29 November 2011. - New York, NY, USA : ACM. - 9781450310086 ; , s. 11-18
-
Konferensbidrag (refereegranskat)abstract
- Recent trends in distributed embedded systems have shown an increase in the amount and heterogeneity of the information that needs to be exchanged, together with a growing importance of supporting dynamic reconfiguration and adaptive behaviors. In this paper we focus on Ethernet technology and we address the case of middle-size networking infrastructure with a few switches. We use the FTT-SE protocol to support dynamic heterogeneous real-time transactions with temporal isolation and we propose the needed scheduling adaptations to support multi-hop network configurations. The paper also includes a companion worst-case response-time analysis that allows verifying the timeliness of the system. Copyright 2011 ACM.
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| 27. |
- Behnam, Moris, et al.
(författare)
-
Multi-core Composability in the Face of Memory Bus Contention
- 2012
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Konferensbidrag (refereegranskat)abstract
- In this paper we describe the problem of achieving composability of independently developed real-time subsystems to be executed on a multicore platform.We evaluate existing work for achieving real-time performance on multicores and illustrate their lack with respect to composability. To better address composability we present a multi-resource server-based scheduling technique to provide predictable performance when composing multiple subsystems on a multicore platform. To achieve composability also on multicore platforms, we propose to add memory-bandwidth as an additional server resource. Tasks within our multi-resource servers are guaranteed both CPU- and memory-bandwidth; thus the performance of a server will become independent of resource usage by tasks in other servers. We are currently implementing multi-resource servers for the Enea’s OSE operating system for a P4080 8-core processor to be tested with software for a 3G-basestation.
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| 28. |
- Behnam, Moris, et al.
(författare)
-
On Optimal Real-time Subsystem-Interface Generation in the Presence of Shared Resources
- 2010
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Ingår i: Proceedings of the 15th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2010. - Bilbao, Spain. - 9781424468508
-
Konferensbidrag (refereegranskat)abstract
- 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. However, supporting resource sharing in HSF is a major challenge, since it increases the amount of CPU resources required to guarantee schedulability of the hard real time tasks, and it decreases the composability at the system level. In this paper, we focus on a compositional framework called the bounded-delay resource open environment (BROE) server, and we identify key parameters of this framework that have a great effect on how the framework will utilize CPU resources. In addition, we show how to select optimal values for these parameters in order to reduce the required CPU resource
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| 29. |
- Behnam, Moris, 1973-, et al.
(författare)
-
Overrun Methods and Resource Holding Times for Hierarchical Scheduling of Semi-Independent Real-Time Systems
- 2010
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Ingår i: IEEE Transactions on Industrial Informatics. - 1551-3203. ; 6:1, s. 93-104
-
Tidskriftsartikel (refereegranskat)abstract
- The Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework toenable compositional schedulability analysis of embedded software systems with real-time properties. Inthis 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 designprocess, in the paper, the proposed methods allow non-intrusive configuration and tuning of subsystemtiming-behaviour via subsystem interfaces for selecting scheduling parameters.This paper considers three methods to handle overruns due to resource sharing between subsystemsin the HSF. For each one of these three overrun methods corresponding scheduling algorithms and associatedschedulability 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 techniqueof calculating resource-holding times within the framework under different scheduling algorithms; theresource holding times being an important parameter in the global schedulability analysis.
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| 30. |
- Behnam, Moris, 1973-, et al.
(författare)
-
Schedulability analysis of synchronization protocols based on overrun without payback for hierarchical scheduling frameworks revisited
- 2010
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we show that both global as well as local schedulability analysis of synchronization protocols based on the stack resource protocol (SRP) and overrun without payback for hierarchical scheduling frameworks based on fixed-priority pre-emptive scheduling (FPPS) are pessimistic.We present improved global and local schedulability analysis,illustrate the improvements by means of examples, and show that the improved global analysis is both uniform and sustainable.We evaluate the improved global and local schedulabilityanalysis based on an extensive simulation study and comparethe results with the existing analysis.
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