1,140 research outputs found
ILP-based approaches to partitioning recurrent workloads upon heterogeneous multiprocessors
The problem of partitioning systems of independent constrained-deadline sporadic tasks upon heterogeneous multiprocessor platforms is considered. Several different integer linear program (ILP) formulations of this problem, offering different tradeoffs between effectiveness (as quantified by speedup bound) and running time efficiency, are presented
Neural Feedback Scheduling of Real-Time Control Tasks
Many embedded real-time control systems suffer from resource constraints and
dynamic workload variations. Although optimal feedback scheduling schemes are
in principle capable of maximizing the overall control performance of
multitasking control systems, most of them induce excessively large
computational overheads associated with the mathematical optimization routines
involved and hence are not directly applicable to practical systems. To
optimize the overall control performance while minimizing the overhead of
feedback scheduling, this paper proposes an efficient feedback scheduling
scheme based on feedforward neural networks. Using the optimal solutions
obtained offline by mathematical optimization methods, a back-propagation (BP)
neural network is designed to adapt online the sampling periods of concurrent
control tasks with respect to changes in computing resource availability.
Numerical simulation results show that the proposed scheme can reduce the
computational overhead significantly while delivering almost the same overall
control performance as compared to optimal feedback scheduling.Comment: To appear in International Journal of Innovative Computing,
Information and Contro
Weak Singular Hybrid Automata
The framework of Hybrid automata, introduced by Alur, Courcourbetis,
Henzinger, and Ho, provides a formal modeling and analysis environment to
analyze the interaction between the discrete and the continuous parts of
cyber-physical systems. Hybrid automata can be considered as generalizations of
finite state automata augmented with a finite set of real-valued variables
whose dynamics in each state is governed by a system of ordinary differential
equations. Moreover, the discrete transitions of hybrid automata are guarded by
constraints over the values of these real-valued variables, and enable
discontinuous jumps in the evolution of these variables. Singular hybrid
automata are a subclass of hybrid automata where dynamics is specified by
state-dependent constant vectors. Henzinger, Kopke, Puri, and Varaiya showed
that for even very restricted subclasses of singular hybrid automata, the
fundamental verification questions, like reachability and schedulability, are
undecidable. In this paper we present \emph{weak singular hybrid automata}
(WSHA), a previously unexplored subclass of singular hybrid automata, and show
the decidability (and the exact complexity) of various verification questions
for this class including reachability (NP-Complete) and LTL model-checking
(PSPACE-Complete). We further show that extending WSHA with a single
unrestricted clock or extending WSHA with unrestricted variable updates lead to
undecidability of reachability problem
k2U: A General Framework from k-Point Effective Schedulability Analysis to Utilization-Based Tests
To deal with a large variety of workloads in different application domains in
real-time embedded systems, a number of expressive task models have been
developed. For each individual task model, researchers tend to develop
different types of techniques for deriving schedulability tests with different
computation complexity and performance. In this paper, we present a general
schedulability analysis framework, namely the k2U framework, that can be
potentially applied to analyze a large set of real-time task models under any
fixed-priority scheduling algorithm, on both uniprocessor and multiprocessor
scheduling. The key to k2U is a k-point effective schedulability test, which
can be viewed as a "blackbox" interface. For any task model, if a corresponding
k-point effective schedulability test can be constructed, then a sufficient
utilization-based test can be automatically derived. We show the generality of
k2U by applying it to different task models, which results in new and improved
tests compared to the state-of-the-art.
Analogously, a similar concept by testing only k points with a different
formulation has been studied by us in another framework, called k2Q, which
provides quadratic bounds or utilization bounds based on a different
formulation of schedulability test. With the quadratic and hyperbolic forms,
k2Q and k2U frameworks can be used to provide many quantitive features to be
measured, like the total utilization bounds, speed-up factors, etc., not only
for uniprocessor scheduling but also for multiprocessor scheduling. These
frameworks can be viewed as a "blackbox" interface for schedulability tests and
response-time analysis
Utilization-Based Scheduling of Flexible Mixed-Criticality Real-Time Tasks
Mixed-criticality models are an emerging paradigm for the design of real-time
systems because of their significantly improved resource efficiency. However,
formal mixed-criticality models have traditionally been characterized by two
impractical assumptions: once \textit{any} high-criticality task overruns,
\textit{all} low-criticality tasks are suspended and \textit{all other}
high-criticality tasks are assumed to exhibit high-criticality behaviors at the
same time. In this paper, we propose a more realistic mixed-criticality model,
called the flexible mixed-criticality (FMC) model, in which these two issues
are addressed in a combined manner. In this new model, only the overrun task
itself is assumed to exhibit high-criticality behavior, while other
high-criticality tasks remain in the same mode as before. The guaranteed
service levels of low-criticality tasks are gracefully degraded with the
overruns of high-criticality tasks. We derive a utilization-based technique to
analyze the schedulability of this new mixed-criticality model under EDF-VD
scheduling. During runtime, the proposed test condition serves an important
criterion for dynamic service level tuning, by means of which the maximum
available execution budget for low-criticality tasks can be directly determined
with minimal overhead while guaranteeing mixed-criticality schedulability.
Experiments demonstrate the effectiveness of the FMC scheme compared with
state-of-the-art techniques.Comment: This paper has been submitted to IEEE Transaction on Computers (TC)
on Sept-09th-201
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