| 31. |
- 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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| 32. |
- Afshar, Sara
(författare)
-
Lock-Based Resource Sharing in Real-Time Multiprocessor Platforms
- 2014
-
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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| 33. |
- Afshar, Sara, et al.
(författare)
-
Per Processor Spin-Lock Priority for Partitioned Multiprocessor Real-Time Systems
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Two traditional approaches exist for a task that is blocked on a global resource; a task either performs a non-preemptive busy wait, i.e., spins, or suspends and releases the processor. Previously, we have shown that both approaches can be viewed as spinning either at the highest priority HP or at the lowest priority on the processor LP, respectively. Based on this view, previously we have generalized a task's blocking behavioral model, as spinning at any arbitrary priority level. In this paper, we focus on a particular class of spin-lock protocols from the introduced flexible spin-lock model where spinning is performed at a priority equal to or higher than the highest local ceiling of the global resources accessed on a processor referred to as CP spin-lock approach. In this paper, we assume that all tasks of a specific processor are spinning on the same priority level. Given this class and assumption, we show that there exists a spin-lock protocol in this range that dominates the classic spin-lock protocol which tasks spin on highest priority level (HP). However we show that this new approach is incomparable with the CP spin-lock approach. Moreover, we show that there may exist an intermediate spin-lock approach between the priority used by CP spin-lock approach and the new introduced spin-lock approach that can make a task set schedulable when those two cannot. We provide an extensive evaluation results comparing the HP, CP and the new proposed approach.
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| 34. |
- Afshar, Sara, et al.
(författare)
-
Per Processor Spin-Lock Priority for Partitioned Multiprocessor Real-Time Systems
- 2017
-
Ingår i: Leibniz Transactions on Embedded Systems. - 2199-2002. ; :2
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Two traditional approaches exist for a task that is blocked on a global resource; a task either performs a non-preemptive busy wait, i.e., spins, or suspends and releases the processor. Previously, we have shown that both approaches can be viewed as spinning either at the highest priority HP or at the lowest priority on the processor LP, respectively. Based on this view, previously we have generalized a task's blocking behavioral model, as spinning at any arbitrary priority level. In this paper, we focus on a particular class of spin-lock protocols from the introduced flexible spin-lock model where spinning is performed at a priority equal to or higher than the highest local ceiling of the global resources accessed on a processor referred to as CP spin-lock approach. In this paper, we assume that all tasks of a specific processor are spinning on the same priority level. Given this class and assumption, we show that there exists a spin-lock protocol in this range that dominates the classic spin-lock protocol which tasks spin on highest priority level (HP). However we show that this new approach is incomparable with the CP spin-lock approach. Moreover, we show that there may exist an intermediate spin-lock approach between the priority used by CP spin-lock approach and the new introduced spin-lock approach that can make a task set schedulable when those two cannot. We provide an extensive evaluation results comparing the HP, CP and the new proposed approach.
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| 35. |
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| 36. |
- Afzal, Wasif, et al.
(författare)
-
Program committee for icse 2018 posters track
- 2018
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Ingår i: Proceedings / International Conference of Software Engineering. - : IEEE Computer Society. - 0270-5257 .- 1558-1225. ; Part F137351
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 37. |
- Afzal, Wasif
(författare)
-
Search-based approaches to software fault prediction and software testing
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Software verification and validation activities are essential for software quality but also constitute a large part of software development costs. Therefore efficient and cost-effective software verification and validation activities are both a priority and a necessity considering the pressure to decrease time-to-market and intense competition faced by many, if not all, companies today. It is then perhaps not unexpected that decisions related to software quality, when to stop testing, testing schedule and testing resource allocation needs to be as accurate as possible. This thesis investigates the application of search-based techniques within two activities of software verification and validation: Software fault prediction and software testing for non-functional system properties. Software fault prediction modeling can provide support for making important decisions as outlined above. In this thesis we empirically evaluate symbolic regression using genetic programming (a search-based technique) as a potential method for software fault predictions. Using data sets from both industrial and open-source software, the strengths and weaknesses of applying symbolic regression in genetic programming are evaluated against competitive techniques. In addition to software fault prediction this thesis also consolidates available research into predictive modeling of other attributes by applying symbolic regression in genetic programming, thus presenting a broader perspective. As an extension to the application of search-based techniques within software verification and validation this thesis further investigates the extent of application of search-based techniques for testing non-functional system properties. Based on the research findings in this thesis it can be concluded that applying symbolic regression in genetic programming may be a viable technique for software fault prediction. We additionally seek literature evidence where other search-based techniques are applied for testing of non-functional system properties, hence contributing towards the growing application of search-based techniques in diverse activities within software verification and validation.
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| 38. |
- Afzal, Wasif
(författare)
-
Search-Based Prediction of Software Quality : Evaluations and Comparisons
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Software verification and validation (V&V) activities are critical for achieving software quality; however, these activities also constitute a large part of the costs when developing software. Therefore efficient and effective software V&V activities are both a priority and a necessity considering the pressure to decrease time-to-market and the intense competition faced by many, if not all, companies today. It is then perhaps not unexpected that decisions that affects software quality, e.g., how to allocate testing resources, develop testing schedules and to decide when to stop testing, needs to be as stable and accurate as possible. The objective of this thesis is to investigate how search-based techniques can support decision-making and help control variation in software V&V activities, thereby indirectly improving software quality. Several themes in providing this support are investigated: predicting reliability of future software versions based on fault history; fault prediction to improve test phase efficiency; assignment of resources to fixing faults; and distinguishing fault-prone software modules from non-faulty ones. A common element in these investigations is the use of search-based techniques, often also called metaheuristic techniques, for supporting the V&V decision-making processes. Search-based techniques are promising since, as many problems in real world, software V&V can be formulated as optimization problems where near optimal solutions are often good enough. Moreover, these techniques are general optimization solutions that can potentially be applied across a larger variety of decision-making situations than other existing alternatives. Apart from presenting the current state of the art, in the form of a systematic literature review, and doing comparative evaluations of a variety of metaheuristic techniques on large-scale projects (both industrial and open-source), this thesis also presents methodological investigations using search-based techniques that are relevant to the task of software quality measurement and prediction. The results of applying search-based techniques in large-scale projects, while investigating a variety of research themes, show that they consistently give competitive results in comparison with existing techniques. Based on the research findings, we conclude that search-based techniques are viable techniques to use in supporting the decision-making processes within software V&V activities. The accuracy and consistency of these techniques make them important tools when developing future decision-support for effective management of software V&V activities.
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| 39. |
- Agerskans, Natalie
(författare)
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Digital Technologies for Enabling Smart Production : Examining the Aspects of Selection and Integration
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the development towards Industry 5.0, manufacturing companies are developing towards smart production. In smart production, data is used as a resource to interconnect different elements in the production system to learn and adapt to changing production conditions. Common objectives include human-centricity, resource-efficiency, and sustainable production. To enable these desired benefits of smart production, there is a need to use digital technologies to create and manage the entire flow of data. To enable smart production, it is essential to deploy digital technologies in a way so that collected raw data is converted into useful data that can be applied by equipment or humans to generate value or reduce waste in production. This requires consideration to the data flow within the production system, i.e., the entire process of converting raw data into useful data which includes data management aspects such as the collection, analysis, and visualization of data. To enable a good data flow, there is a need to combine several digital technologies. However, many manufacturing companies are facing challenges when selecting suitable digital technologies for their specific production system. Common challenges are related to the overwhelming number of advanced digital technologies available on the market, and the complexity of production system and digital technologies. This makes it a complex task to understand what digital technologies to select and the recourses and actions needed to integrate them in the production system.Against this background, the purpose of this licentiate thesis is to examine the selection and integration of digital technologies to enable smart production within manufacturing companies. More specifically, this licentiate thesis examines the challenges and critical factors of selecting and integrating digital technologies for smart production. This was accomplished by performing a qualitative-based multiple case study involving manufacturing companies within different industries and of different sizes. The findings show that identified challenges and critical factors are related to the different phases of the data value chain: data sources and collection, data communication, data processing and storage, and data visualisation and usage. General challenges and critical factors that were related to all phases of the data value chain were also identified. Moreover, the challenges and critical factors were related to people, process, and technology aspects. This shows that there is a need for holistic perspective on the entire data value chain and different production system elements when digital technologies are selected and integrated. Furthermore, there is a need to define a structured process for the selection and integration of digital technologies, where both management and operational level are involved.
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| 40. |
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