| 1. |
- Aminifar, Amir, et al.
(författare)
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Analysis and Design of Real-Time Servers for Control Applications
- 2016
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Ingår i: IEEE Transactions on Computers. - : IEEE COMPUTER SOC. - 0018-9340 .- 1557-9956. ; 65:3, s. 834-846
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Tidskriftsartikel (refereegranskat)abstract
- Today, a considerable portion of embedded systems, e.g., automotive and avionic, comprise several control applications. Guaranteeing the stability of these control applications in embedded systems, or cyber-physical systems, is perhaps the most fundamental requirement while implementing such applications. This is different from the classical hard real-time systems where often the acceptance criterion is meeting the deadline. In other words, in the case of control applications, guaranteeing stability is considered to be a main design goal, which is linked to the amount of delay and jitter a control application can tolerate before instability. This advocates the need for new design and analysis techniques for embedded real-time systems running control applications. In this paper, the analysis and design of such systems considering a server-based resource reservation mechanism are addressed. The benefits of employing servers are manifold: providing a compositional and scalable framework, protection against other tasks misbehaviors, and systematic bandwidth assignment and co-design. We propose a methodology for designing bandwidth-optimal servers to stabilize control tasks. The pessimism involved in the proposed methodology is both discussed theoretically and evaluated experimentally.
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| 2. |
- Aminifar, Amir, et al.
(författare)
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Optimization of Message Encryption for Real-Time Applications in Embedded Systems
- 2018
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Ingår i: IEEE Transactions on Computers. - : IEEE. - 0018-9340 .- 1557-9956. ; 67:5, s. 748-754
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Tidskriftsartikel (refereegranskat)abstract
- Today, security can no longer be treated as a secondary issue in embedded and cyber-physical systems. Therefore, one of the main challenges in these domains is the design of secure embedded systems under stringent resource constraints and real-time requirements. However, there exists an inherent trade-off between the security protection provided and the amount of resources allocated for this purpose. That is, the more the amount of resources used for security, the higher the security, but the fewer the number of applications which can be run on the platform and meet their timing requirements. This trade-off is of high importance since embedded systems are often highly resource constrained. In this paper, we propose an efficient solution to maximize confidentiality, while also guaranteeing the timing requirements of real-time applications on shared platforms.
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| 3. |
- Amirijoo, Mehdi, et al.
(författare)
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Specification and Management of QoS in Real-Time Databases Supporting Imprecise Computations
- 2006
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Ingår i: IEEE Transactions on Computers. - 0018-9340 .- 1557-9956. ; 55:3, s. 304-319
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Tidskriftsartikel (refereegranskat)abstract
- Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services that are provided by real-time databases. Since the workload of real-time databases cannot be precisely predicted, they can become overloaded and thereby cause temporal violations, resulting in damage or even a catastrophe. Imprecise computation techniques address this problem and allow graceful degradation during overloads. In this paper, we present a framework for QoS specification and management consisting of a model for expressing QoS requirements, an architecture based on feedback control scheduling, and a set of algorithms implementing different policies and behaviors. Our approach gives a robust and controlled behavior of real-time databases, even for transient overloads and with inaccurate runtime estimates of the transactions. Further, performance experiments show that the proposed algorithms outperform a set of baseline algorithms that uses feedback control.
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| 4. |
- Arlat, Jean, et al.
(författare)
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Comparison of Physical and Software-Implemented Fault Injection Techniques
- 2003
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Ingår i: IEEE Transactions on Computers. - 0018-9340. ; 52:9, s. 1115-1133
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the issue of characterizing the respective impact of fault injection techniques. Three physical techniques and one software-implemented technique that have been used to assess the fault tolerance features of the MARS fault-tolerant distributed real-time system are compared and analyzed. After a short summary of the fault tolerance features of the MARS architecture and especially of the error detection mechanisms that were used to compare the erroneous behaviors induced by the fault injection techniques considered, we describe the common distributed testbed and test scenario implemented to perform a coherent set of fault injection campaigns. The main features of the four fault injection techniques considered are then briefly described and the results obtained are finally presented and discussed. Emphasis is put on the analysis of the specific impact and merit of each injection technique.
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| 5. |
- Bartlett, Mark, et al.
(författare)
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Accurate Determination of Loop Iterations for Worst-Case Execution Time Analysis
- 2010
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Ingår i: IEEE Transactions on Computers. - 0018-9340 .- 1557-9956. ; 59:12, s. 1520-1532
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Tidskriftsartikel (refereegranskat)abstract
- Determination of accurate estimates for the Worst-Case Execution Time of a program is essential for guaranteeing the correct temporal behavior of any Real-Time System. Of particular importance is tightly bounding the number of iterations of loops in the program or excessive undue pessimism can result. This paper presents a novel approach to determining the number of iterations of a loop for such analysis. Program traces are collected and analyzed allowing the number of loop executions to be parametrically determined safely and precisely under certain conditions. The approach is mathematically proved to be safe and its practicality is demonstrated on a series of benchmarks.
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| 6. |
- Bini, Enrico
(författare)
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The Quadratic Utilization Upper Bound for Arbitrary Deadline Real-Time Tasks
- 2015
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Ingår i: IEEE Transactions on Computers. - 0018-9340. ; 64:2, s. 593-599
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Tidskriftsartikel (refereegranskat)abstract
- In high throughput applications, such as in multimedia, it is preferable to fully utilize computing resources, even at the price of some (bounded) delay. However, in real-time systems, where the maximum admissible delay is modeled by a deadline, most of the theory is developed with the assumption of a task deadline smaller than or equal to the task period. The reason of this limitation is in the intrinsic difficulty of the schedulability analysis in the arbitrary deadline case. The most notable guarantee test for sets of arbitrary deadline tasks was due to Lehoczky in 1990. In this paper, we propose the quadratic utilization bound applicable to tasks with arbitrary deadline, which extends Lehoczky’s result. The improvement is made possible by providing some information about the task periods.
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| 7. |
- Bini, Enrico, et al.
(författare)
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Zero-Jitter Chains of Periodic LET Tasks via Algebraic Rings
- 2023
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Ingår i: IEEE Transactions on Computers. - 0018-9340. ; 72:11, s. 3057-3071
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Tidskriftsartikel (refereegranskat)abstract
- In embedded computing domains, including the automotive industry, complex functionalities are split across multiple tasks that form task chains. These tasks are functionally dependent and communicate partial computations through shared memory slots based on the Logical Execution Time (LET) paradigm. This paper introduces a model that captures the behavior of a producer-consumer pair of tasks in a chain, characterizing the timing of reading and writing events. Using ring algebra, the combined behavior of the pair can be modeled as a single periodic task. The paper also presents a lightweight mechanism to eliminate jitter in an entire chain of any size, resulting in a single periodic LET task with zero jitter. All presented methods are available in a public repository.
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| 8. |
- Cantoro, Riccardo, et al.
(författare)
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Test of Reconfigurable Modules in Scan Networks
- 2018
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Ingår i: IEEE Transactions on Computers. - 0018-9340. ; 67:12, s. 1806-1817
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Tidskriftsartikel (refereegranskat)abstract
- Modern devices often include several embedded instruments, such as BIST interfaces, sensors, calibration facilities. New standards, such as IEEE Std 1687, provide vehicles to access these instruments. In approaches based on reconfigurable scan networks (RSNs), instruments are coupled with scan registers, connected into chains and interleaved with reconfigurable modules. Such modules embed reconfigurable multiplexers that permit a selective access to different parts of the chain. A similar scenario is also supported by IEEE Std 1149.1-2013. The test of permanent faults affecting an RSN requires to shift test vectors throughout a certain number of network configurations. This paper presents some methodologies to select the list of configurations that perform the complete test of the reconfigurable modules of the RSN. In particular, one method is presented that, by construction, can be proved to be able to apply the test in the minimum amount of clock cycles. Other methods are sub-optimal in terms of test application time (TAT), but scale well on large circuits. In order to provide a comparison between the proposed methods, experimental results on some benchmark RSNs are provided.
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| 9. |
- Cederman, Daniel, 1981, et al.
(författare)
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Supporting Lock-Free Composition of Concurrent Data Objects: Moving Data Between Containers
- 2013
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Ingår i: IEEE Transactions on Computers. - 0018-9340. ; 62:9, s. 1866-1878
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Tidskriftsartikel (refereegranskat)abstract
- Lock-free data objects offer several advantages over their blocking counterparts, such as being immune to deadlocks, priority inversion and convoying. They have also been shown to work well in practice. However, composing the operations they provide into larger atomic operations, while still guaranteeing efficiency and lock-freedom, is a challenging algorithmic task. We present a lock-free methodology for composing a wide variety of concurrent linearizable objects together by unifying their linearization points. This makes it possible to relatively easily introduce atomic lock-free move operations to a wide range of concurrent lock-free containers. This move operation allows data to be transferred from one container to another, in a lock-free way, without blocking any of the operations supported by the original container. For a data object to be suitable for composition using our methodology it needs to fulfil a set of requirements. These requirement are however generic enough to be fulfilled by a large set of objects. To show this we have performed case studies on six commonly used lock-free objects (a stack, a queue, a skip-list, a deque, a doubly linked-list and a hash-table) to demonstrate the general applicability of the methodology. We also show that the operations originally supported by the data objects keep their performance behavior under our methodology.
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| 10. |
- Charif, Amir, et al.
(författare)
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First-Last: A Cost-Effective Adaptive Routing Solution for TSV-Based Three-Dimensional Networks-on-Chip
- 2018
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Ingår i: IEEE Transactions on Computers. - 0018-9340 .- 1557-9956. ; 67:10, s. 1430-1444
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Tidskriftsartikel (refereegranskat)abstract
- 3D integration opens up new opportunities for future multiprocessor chips by enabling fast and highly scalable 3DNetwork-on-Chip (NoC) topologies. However, in an aim to reduce the cost of Through-silicon via (TSV), partially vertically connectedNoCs, in which only a few vertical TSV links are available, have been gaining relevance. To reliably route packets under suchconditions, we introduce a lightweight, efficient and highly resilient adaptive routing algorithm targeting partially vertically connected3D-NoCs named First-Last. It requires a very low number of virtual channels (VCs) to achieve deadlock-freedom (2 VCs in the Eastand North directions and 1 VC in all other directions), and guarantees packet delivery as long as one healthy TSV connecting all layersis available anywhere in the network. An improved version of our algorithm, named Enhanced-First-Last is also introduced and shownto dramatically improve performance under low TSV availability while still using less virtual channels than state-of-the-art algorithms. Acomprehensive evaluation of the cost and performance of our algorithms is performed to demonstrate their merits with respects toexisting solutions.
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