13,980 research outputs found
TASKers: A Whole-System Generator for Benchmarking Real-Time-System Analyses
Implementation-based benchmarking of timing and schedulability analyses requires system code that can be executed on real hardware and has defined properties, for example, known worst-case execution times (WCETs) of tasks. Traditional approaches for creating benchmarks with such characteristics often result in implementations that do not resemble real-world systems, either due to work only being simulated by means of busy waiting, or because tasks have no control-flow dependencies between each other. In this paper, we address this problem with TASKers, a generator that constructs realistic benchmark systems with predefined properties. To achieve this, TASKers composes patterns of real-world programs to generate tasks that produce known outputs and exhibit preconfigured WCETs when being executed with certain inputs. Using this knowledge during the generation process, TASKers is able to specifically introduce inter-task control-flow dependencies by mapping the output of one task to the input of another
Controlling Concurrent Change - A Multiview Approach Toward Updatable Vehicle Automation Systems
The development of SAE Level 3+ vehicles [{SAE}, 2014] poses new challenges not only for the functional development, but also for design and development processes. Such systems consist of a growing number of interconnected functional, as well as hardware and software components, making safety design increasingly difficult. In order to cope with emergent behavior at the vehicle level, thorough systems engineering becomes a key requirement, which enables traceability between different design viewpoints. Ensuring traceability is a key factor towards an efficient validation and verification of such systems. Formal models can in turn assist in keeping track of how the different viewpoints relate to each other and how the interplay of components affects the overall system behavior. Based on experience from the project Controlling Concurrent Change, this paper presents an approach towards model-based integration and verification of a cause effect chain for a component-based vehicle automation system. It reasons on a cross-layer model of the resulting system, which covers necessary aspects of a design in individual architectural views, e.g. safety and timing. In the synthesis stage of integration, our approach is capable of inserting enforcement mechanisms into the design to ensure adherence to the model. We present a use case description for an environment perception system, starting with a functional architecture, which is the basis for componentization of the cause effect chain. By tying the vehicle architecture to the cross-layer integration model, we are able to map the reasoning done during verification to vehicle behavior
Considering Human Aspects on Strategies for Designing and Managing Distributed Human Computation
A human computation system can be viewed as a distributed system in which the
processors are humans, called workers. Such systems harness the cognitive power
of a group of workers connected to the Internet to execute relatively simple
tasks, whose solutions, once grouped, solve a problem that systems equipped
with only machines could not solve satisfactorily. Examples of such systems are
Amazon Mechanical Turk and the Zooniverse platform. A human computation
application comprises a group of tasks, each of them can be performed by one
worker. Tasks might have dependencies among each other. In this study, we
propose a theoretical framework to analyze such type of application from a
distributed systems point of view. Our framework is established on three
dimensions that represent different perspectives in which human computation
applications can be approached: quality-of-service requirements, design and
management strategies, and human aspects. By using this framework, we review
human computation in the perspective of programmers seeking to improve the
design of human computation applications and managers seeking to increase the
effectiveness of human computation infrastructures in running such
applications. In doing so, besides integrating and organizing what has been
done in this direction, we also put into perspective the fact that the human
aspects of the workers in such systems introduce new challenges in terms of,
for example, task assignment, dependency management, and fault prevention and
tolerance. We discuss how they are related to distributed systems and other
areas of knowledge.Comment: 3 figures, 1 tabl
Reservation-Based Federated Scheduling for Parallel Real-Time Tasks
This paper considers the scheduling of parallel real-time tasks with
arbitrary-deadlines. Each job of a parallel task is described as a directed
acyclic graph (DAG). In contrast to prior work in this area, where
decomposition-based scheduling algorithms are proposed based on the
DAG-structure and inter-task interference is analyzed as self-suspending
behavior, this paper generalizes the federated scheduling approach. We propose
a reservation-based algorithm, called reservation-based federated scheduling,
that dominates federated scheduling. We provide general constraints for the
design of such systems and prove that reservation-based federated scheduling
has a constant speedup factor with respect to any optimal DAG task scheduler.
Furthermore, the presented algorithm can be used in conjunction with any
scheduler and scheduling analysis suitable for ordinary arbitrary-deadline
sporadic task sets, i.e., without parallelism
Securing Real-Time Internet-of-Things
Modern embedded and cyber-physical systems are ubiquitous. A large number of
critical cyber-physical systems have real-time requirements (e.g., avionics,
automobiles, power grids, manufacturing systems, industrial control systems,
etc.). Recent developments and new functionality requires real-time embedded
devices to be connected to the Internet. This gives rise to the real-time
Internet-of-things (RT-IoT) that promises a better user experience through
stronger connectivity and efficient use of next-generation embedded devices.
However RT- IoT are also increasingly becoming targets for cyber-attacks which
is exacerbated by this increased connectivity. This paper gives an introduction
to RT-IoT systems, an outlook of current approaches and possible research
challenges towards secure RT- IoT frameworks
Modeling, Analysis, and Hard Real-time Scheduling of Adaptive Streaming Applications
In real-time systems, the application's behavior has to be predictable at
compile-time to guarantee timing constraints. However, modern streaming
applications which exhibit adaptive behavior due to mode switching at run-time,
may degrade system predictability due to unknown behavior of the application
during mode transitions. Therefore, proper temporal analysis during mode
transitions is imperative to preserve system predictability. To this end, in
this paper, we initially introduce Mode Aware Data Flow (MADF) which is our new
predictable Model of Computation (MoC) to efficiently capture the behavior of
adaptive streaming applications. Then, as an important part of the operational
semantics of MADF, we propose the Maximum-Overlap Offset (MOO) which is our
novel protocol for mode transitions. The main advantage of this transition
protocol is that, in contrast to self-timed transition protocols, it avoids
timing interference between modes upon mode transitions. As a result, any mode
transition can be analyzed independently from the mode transitions that
occurred in the past. Based on this transition protocol, we propose a hard
real-time analysis as well to guarantee timing constraints by avoiding
processor overloading during mode transitions. Therefore, using this protocol,
we can derive a lower bound and an upper bound on the earliest starting time of
the tasks in the new mode during mode transitions in such a way that hard
real-time constraints are respected.Comment: Accepted for presentation at EMSOFT 2018 and for publication in IEEE
Transactions on Computer-Aided Design of Integrated Circuits and Systems
(TCAD) as part of the ESWEEK-TCAD special issu
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