| 1. |
- Yin, Hang, 1982-
(författare)
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Introducing Mode Switch in Component-Based Software Development
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-adaptivity, characterized by the ability to dynamically adjust behavior at runtime, is a growing trend in the evolution of modern embedded systems. While self-adaptive systems tend to be flexible and autonomous, self-adaptivity may inevitably complicate software design, test and analysis. A strategy for taming the growing software complexity of self-adaptive systems is to partition system behaviors into different operational modes specified at design time. Such a multi-mode system can change behavior by switching between modes at runtime under certain circumstances. Multi-mode systems can benefit from a complementary approach to the software development of complex systems: Component-Based Software Engineering (CBSE), which fosters reuse of independently developed software components. However, the state-of-the-art component-based development of multi-mode systems does not take full advantage of CBSE, as reuse of modes at component level is barely addressed. Modes are often treated as system properties, while mode switches are handled by a global mode manager. This centralized mode management entails global information of all components, whereas the global information may be inaccessible in component-based systems. Another potential problem is that a single mode manager does not scale well, particularly at design time, for a large number of components and modes. In this thesis we propose a distributed solution to the component-based development of multi-mode systems, aiming for a more efficient and scalable mode management. Our goal is to fully incorporate modes in software component reuse, supporting reuse of multi-mode components, i.e., components able to run in multiple modes. We have developed a generic framework, the Mode-Switch Logic (MSL), which not only supports reuse of multi-mode components but also provides runtime mechanisms for handling mode switch. MSL includes three fundamental elements: (1) a mode-aware component model with the formal specification of reusable multi-mode software components; (2) a mode mapping mechanism for the seamless composition of multi-mode components; and (3) a mode-switch runtime mechanism which is executed by each component in isolation from its functional execution and coordinates the mode switches of different components without the need of global mode information. The mode-switch runtime mechanism has been verified by model checking in conjunction with mathematical proofs. We also provide a mode-switch timing analysis for the runtime mechanism to respect real-time requirements. MSL is dedicated to the mode aspect of a system irrespective of component execution semantics, thus independent of the choice of component models. We have integrated MSL in the ProCom component model with the extension of support for reuse of multi-mode components and distributed mode-switch handling. Although the distributed mode-switch handling of MSL is more flexible and scalable than the conventional centralized approach, when components are deployed on a single hardware platform and global mode information is available, centralized mode-switch handling is more efficient in terms of runtime overhead and mode-switch time. Hence, MSL is supplemented with a mode transformation technique to enhance runtime mode-switch efficiency by converting the distributed mechanism to a centralized mechanism. MSL together with the mode transformation technique has been implemented in a prototype tool where one can build multi-mode systems by reusing multi-mode components. The applicability of MSL is demonstrated in two proof-of-concept case studies.
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| 2. |
- Afshar, Sara
(författare)
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Lock-Based Resource Sharing for Real-Time Multiprocessors
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are widely used in the industry and are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory might be limited in the system. Hence, techniques that can enable an efficient usage of processor bandwidths in such systems are of great importance. Locked-based resource sharing protocols are proposed as a solution to overcome resource limitation by allowing the available resources in the system to be safely shared. In recent years, due to a dramatic enhancement in the functionality of systems, a shift from single-core processors to multi-core processors has become inevitable from an industrial perspective to tackle the raised challenges due to increased system complexity. However, the resource sharing protocols are not fully mature for multi-core processors. The two classical multi-core processor resource sharing protocols, spin-based and suspension-based protocols, although providing mutually exclusive access to resources, can introduce long blocking delays to tasks, which may be unacceptable for many industrial applications. In this thesis we enhance the performance of resource sharing protocols for partitioned scheduling, which is the de-facto scheduling standard for industrial real-time multi-core processor systems such as in AUTOSAR, in terms of timing and memory requirements. A new scheduling approach uses a resource efficient hybrid approach combining both partitioned and global scheduling where the partitioned scheduling is used to schedule the major number of tasks in the system. In such a scheduling approach applications with critical task sets use partitioned scheduling to achieve higher level of predictability. Then the unused bandwidth on each core that is remained from partitioning is used to schedule less critical task sets using global scheduling to achieve higher system utilization. These scheduling schema however lacks a proper resource sharing protocol since the existing protocols designed for partitioned and global scheduling cannot be directly applied due to the complex hybrid structure of these scheduling frameworks. In this thesis we propose a resource sharing solution for such a complex structure. Further, we provide the blocking bounds incurred to tasks under the proposed protocols and enhance the schedulability analysis, which is an essential requirement for real-time systems, with the provided blocking bounds.
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| 3. |
- Becker, Matthias, 1986-
(författare)
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Efficient Resource Management for Many-Core based Industrial Real-Time Systems
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increased complexity of today’s industrial embedded systems stands inneed for more computational power while most systems must adhere to a restrictedenergy consumption, either to prolong the battery lifetime or to reduceoperational costs. The many-core processor is therefore a natural fit. Due tothe simple architecture of the compute cores, and therefore their good analyzability,such processors are additionally well suited for real-time applications.In our research, we focus on two particular problems which need to be addressedin order to pave the way into the many-core era. The first area is powerand thermal aware execution frameworks, where we present different energyaware extensions to well known load balancing algorithms, allowing them todynamically scale the number of active cores depending on their workload.In contrast, an additional framework is presented which balances workloadsto minimize temperature gradients on the die. The second line of works focuseson industrial standards in the face of massively parallel platforms, wherewe address the automotive and automation domain. We present an executionframework for IEC 61131-3 applications, allowing the consolidation of severalIEC 61131-3 applications on the same platform. Additionally, we discussseveral architectural options for the AUTOSAR software architecture on suchmassively parallel platforms.
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| 4. |
- Bujosa Mateu, Daniel
(författare)
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Enhancing TSN Adoption by Industry : Tools to Support Migrating Ethernet-based Legacy Networks into TSN
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New technologies present opportunities and challenges for industries. One major challenge is the ease, or even feasibility, of its adoption. The Time-Sensitive Networking (TSN) standards offer a range of features relevant to various applications and are key for the transition to Industry 4.0. These features include deterministic zero-jitter, low-latency data transmission, transmission of traffic with various levels of time-criticality on the same network, fault tolerance mechanisms, and advanced network management allowing dynamic reconfiguration.This thesis aims to develop tools that enable the industry to adopt TSN easily and efficiently. Specifically, we create tools that facilitate the migration of legacy networks to TSN, enabling the preservation of most of the legacy systems and solutions while reducing costs and adoption time. Firstly, we introduce LETRA (Legacy Ethernet-based Traffic Mapping Tool), a tool for mapping Ethernet-based legacy traffic to the new TSN traffic classes. Secondly, we develop HERMES (Heuristic Multi-queue Scheduler), a heuristic Time-Triggered (TT) traffic scheduler that can meet the characteristics of legacy systems and provide quick results suitable for reconfiguration. Thirdly, we develop TALESS (TSN with Legacy End-Stations Synchronization), a mechanism to avoid adverse consequences caused by the lack of synchronization between legacy systems and TSN-based ones, as not all legacy systems need to support the TSN synchronization mechanisms. Finally, we improve Stream Reservation Protocol (SRP) to enhance Audio-Video Bridging (AVB) traffic configuration in terms of termination and consistency.
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| 5. |
- Johansson, Bjarne, 1977-
(författare)
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Dependable Distributed Control System : Redundancy and Concurrency defects
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Intelligent devices, interconnectivity, and information exchange are characteristics often associated with Industry 4.0. A peer-to-peer-oriented architecture with the network as the system center succeeds the traditional controller-centric topology used in today's distributed control systems, improving information exchange in future designs. The network-centric architecture allows IT-solution such as cloud, fog, and edge computing to enter the automation industry. IT-solution that rely on virtualization techniques such as virtual machines and containers. Virtualization technology, combined with virtual instance management, provide the famous elasticity that cloud computing offer. Container management systems like Kubernetes can scale the number of containers to match the service demand and redeploy containers affected by failures.Distributed control systems constitute automation infrastructure core in many critical applications and domains. The criticality puts high dependability requirements upon the systems, i.e., dependability is essential. High-quality software and redundancy solutions are examples of traditional ways to increase dependability. Dependability is the common denominator for the challenges addressed in this thesis. Challenges that range from concurrency defect localization with static code analysis to utilization of failure recovery mechanisms provided by container management systems in a control system context.We evaluate the feasibility of locating concurrency defects in embedded industrial software with static code analysis. Furthermore, we propose a deployment agnostic failure detection and role selection mechanism for controller redundancy in a network-centric context. Finally, we use the container management system Kubernetes to orchestrate a cluster of virtualized controllers. We evaluate the failure recovery properties of the container management system in combination with redundant virtualized controllers - redundant controllers using the proposed failure detection and role selection solution.
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| 6. |
- Lu, Yue
(författare)
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Pragmatic Approaches for Timing Analysis of Real-Time Embedded Systems
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many industrial real-time embedded systems are very large, flexible and highly configurable software systems. Such systems are becoming ever more complex, and we are reaching the stage in which even if existing timing analysis was feasible from a cost and technical perspective, the analysis results are overly pessimistic, making them less useful to practitioners. When combined with the fact that most existing real-time embedded systems tend to be probabilistic in nature due to high complexity featured by advanced hardware and more flexible and/or adaptive software applications, this advocates moving toward pragmatic timing analysis, which is not specifically limited by constrains related to intricate task execution and temporal dependencies in systems. In this thesis, we address this challenge, and we present two pragmatic timing analysis techniques for real-time embedded systems.The first contribution is a simulation-based analysis using two simple yet novel search algorithms of meta-heuristic type, i.e., a form of genetic algorithms and hill-climbing with random restarts, yielding substantially better results, comparing traditional Monte Carlo simulation-based analysis methods.As the second contribution, we discuss one major issue when using simulation-based methods for timing analysis of real-time embedded systems, i.e., model validity, which determines whether a simulation model is an accurate representation of the target system at the certain level of satisfaction, from a task response time and execution time perspective.The third contribution is a statistical timing analysis, which, unlike the traditional timing analysis, does not require worst-case execution times of tasks as inputs, and computes a probabilistic task worst-case response time estimate pertaining to a configurable task reliability requirement.In addition, a number of tools have been implemented and used for the evaluation of our research results. Our evaluations, using different simulation models depicting fictive but representative industrial control applications, have shown a clear indication that our new timing analysis techniques have the potential to be both applicable and useful in practice, as well as being complementary to software testing focusing on timing properties of real-time embedded systems that are used in various domains of industrial automation, aerospace and defense, automotive telematics, etc.
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| 7. |
- Nemati, Farhang, Senior Lecturer, 1975-
(författare)
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Partitioned Scheduling of Real-Time Tasks on Multi-core Platforms
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years multiprocessor architectures have become mainstream, and multi-core processors are found in products ranging from small portable cell phones to large computer servers. In parallel, research on real-time systems has mainly focused on traditional single-core processors. Hence, in order for real-time systems to fully leverage on the extra capacity offered by new multi-core processors, new design techniques, scheduling approaches, and real-time analysis methods have to be developed.In the multi-core and multiprocessor domain there are mainly two scheduling approaches, global and partitioned scheduling. Under global scheduling each task can execute on any processor at any time while under partitioned scheduling tasks are statically allocated to processors and migration of tasks among processors is not allowed. Besides simplicity and efficiency of partitioned scheduling protocols, existing scheduling and synchronization methods developed for single-core processor platforms can more easily be extended to partitioned scheduling. This also simplifies migration of existing systems to multi-cores. An important issue related to partitioned scheduling is distribution of tasks among processors which is a bin-packing problem.In this thesis we propose a partitioning framework for distributing tasks on the processors of multi-core platforms. Depending on the type of performance we desire to achieve, the framework may distribute a task set differently, e.g., in an application in which tasks process huge amounts of data the goal of the framework may be to decrease cache misses.Furthermore, we propose a blocking-aware partitioning heuristic algorithm to distribute tasks onto the processors of a multi-core architecture. The objective of the proposed algorithm is to decrease blocking overhead of tasks which reduces the total utilization and has the potential to reduce the number of required processors.Finally, we have implemented a tool to facilitate evaluation and comparison of different multiprocessor scheduling and synchronization approaches, as well as different partitioning heuristics. We have applied the tool in the evaluation of several partitioning heuristic algorithms, and the tool is flexible to which any new scheduling or synchronization protocol as well as any new partitioning heuristic can easily be added.
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| 8. |
- Afshar, Sara
(författare)
-
Lock-Based Resource Sharing in Real-Time Multiprocessor Platforms
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded systems are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory can be limited for tasks in the system. Therefore, techniques that enable an efficient usage of such resources are of great importance.In the industry, typically large and complex software systems are divided into smaller parts (applications) where each part is developed independently. Migration towards multiprocessor platforms has become inevitable from an industrial perspective. Due to such migration and to efficient use of system resources, these applications eventually may be integrated on a shared multiprocessor platform. In order to facilitate the integration phase of the applications on a shared platform, the timing and resource requirements of each application can be provided in an interface when the application is developed. The system integrator can benefit from such provided information in the interface of each application to ease the integration process. In this thesis, we have provided the resource and timing requirements of each application in their interfaces for applications that may need several processors to be allocated on when they are developed.Although many scheduling techniques have been studied for multiprocessor systems, these techniques are usually based on the assumption that tasks are independent, i.e. do not share resources other than the processors. This assumption is typically not true. In this thesis, we provide an extension to such systems to handle sharing of resources other than processor among tasks. Two traditional approaches exist for multiprocessor systems to schedule tasks on processors. A recent scheduling approach for multiprocessors has combined the two traditional approaches and achieved a hybrid more efficient approach compared to the two previous one. Due to the complex nature of this scheduling approach the conventional approaches for resource sharing could not be used straight forwardly. In this thesis, we have modified resource sharing approaches such that they can be used in such hybrid scheduling systems. A second concern is that enabling resource sharing in the systems can cause unpredictable delays and variations in response time of tasks which can degrade system performance. Therefore, it is of great significance to improve the resource handling techniques to reduce the effect of imposed delays caused by resource sharing in a multiprocessor platform. In this thesis we have proposed alternative techniques for resource handling that can improve system performance for special setups.
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| 9. |
- Ashjaei, Mohammad, 1980-
(författare)
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Multi-Hop Real-Time Communication over Switched Ethernet Technology
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Switched Ethernet technology has been introduced to be exploited in real-time communication systems due to its features such as its high throughput and wide availability, hence being a cost-effective solution. Many real-time switched Ethernet protocols have been developed, preserving the profits of traditional Ethernet technology, to overcome the limitations imposed by using commercially available (COTS) switches. These limitations mainly originate from the non-deterministic behavior of the Ethernet switches inherent in the use of FIFO queues and a limited number of priority levels. In our research we focus on two particular real-time communication technologies, one based on COTS Ethernet switches named the FTT-SE architecture and the other using a modified Ethernet switch called the HaRTES architecture. Both architectures are based on a master-slave technique supporting different and temporally isolated traffic types including real-time periodic, real-time sporadic and non-real-time traffic. Also, they provide mechanisms implementing adaptivity as a response to the requirements imposed by dynamic real-time applications. Nevertheless, the two mentioned architectures were originally developed for a simple network consisting of a single switch, and they were lacking support for multi-hop communication. In industrial applications, multi-hop communication is essential as the networks comprise a high number of nodes, that is far beyond the capability of a single switch. In this thesis, we study the challenges of building multi-hop communication using the FTT-SE and the HaRTES architectures. We propose different architectures to provide multi-hop communication while preserving the key characteristics of the single-switch architecture such as timeliness guarantee, resource efficiency, adaptivity and dynamicity. We develop a response time analysis for each proposed architecture and we compare them to assess their corresponding benefits and limitations. Further, we develop a simulation tool to evaluate the solutions.
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| 10. |
- Ashjaei, Mohammad, 1980-
(författare)
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Real-Time Communication over Switched Ethernet with Resource Reservation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to the need for advanced computer-controlled functionality in distributed embedded systems the requirements on network communication are becoming overly intricate. This dissertation targets the requirements that are concerned with real-time guarantees, run-time adaptation, resource utilization and flexibility during the development. The Flexible Time-Triggered Switched Ethernet (FTT-SE) and Hard Real-Time Ethernet Switching (HaRTES) network architectures have emerged as two promising solutions that can cater for these requirements. However, these architectures do not support multi-hop communication as they are originally developed for single-switch networks. This dissertation presents a fundamental contribution in multi-hop real-time communication over the FTT-SE and HaRTES architectures targeting the above mentioned requirements. It proposes and evaluates various solutions for scheduling and forwarding the traffic through multiple switches in these architectures. These solutions preserve the ability of dynamic adaptation without jeopardizing real-time properties of the architectures. Moreover, the dissertation presents schedulability analyses for the timeliness verification and evaluation of the proposed solutions as well as several protocols to support run-time adaptation in the multi-hop communication. Finally, the work led to an end-to-end resource reservation framework, based on the proposed multi-hop architectures, to support flexibility during the development of the systems. The efficiency of the proposed solutions is evaluated on various case studies that are inspired from industrial systems.
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