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The fact that energy is a scarce resource in many embedded real-time systems creates the need for energy-aware task schedulers, which not only guarantee timing constraints but also consider energy consumption. Unfortunately, existing approaches to analyze the worst-case execution time (WCET) of a task usually cannot be directly applied to determine its worst-case energy consumption (WCEC) due to execution...
The Quasi-Partitioning Scheduling algorithm optimally solves the problem of scheduling a feasible set of independent implicit-deadline sporadic tasks on a symmetric multiprocessor. It iteratively combines bin-packing solutions to determine a feasible task-to-processor allocation, splitting task loads as needed along the way so that the excess computation on one processor is assigned to a paired processor...
Recent developments in embedded hardware have empowered human experiences through pervasive computing. While embedded systems are becoming more powerful, they still fall short when faced with users' growing desire for running more resource-demanding applications. To bridge this gap, one solution is to leverage powerful resources residing at remote sites by performing computation offloading. Unfortunately,...
Engine control applications include software tasks that are triggered at predetermined angular values of the crankshaft, thus generating a computational workload that varies with the engine speed. To avoid overloads at high rotation speeds, these tasks are implemented to self adapt and reduce their computational demand by switching mode at given rotation speeds. For this reason, they are referred...
During the design phase of many real-time systems, designers often have a range of acceptable period values for which some levels of safety or quality of service are guaranteed. The choice of period values influences system schedulability and computational complexity of schedulability analysis, especially for the rate monotonic (RM) scheduling algorithm. It has been shown that RM guarantees 100% utilization...
Schedulability analysis for real-time systems has been the subject of prominent research over the past several decades. One of the key foundations of schedulability analysis is an accurate worst case execution time (WCET) measurement for each task. In real-time systems that support preemption, the cache related preemption delay (CRPD) can represent a significant component (up to 44% as documented...
Multi-core platforms represent the answer of the industry to the increasing demand for computational capabilities. From a real-time perspective, however, the inherent sharing of resources, such as memory subsystem and I/O channels, creates inter-core timing interference among critical tasks and applications deployed on different cores. As a result, modular per-core certification cannot be performed,...
In modern Commercial Off-The-Shelf (COTS) mul-ticore systems, each core can generate many parallel memory requests at a time. The processing of these parallel requests in the DRAM controller greatly affects the memory interference delay experienced by running tasks on the platform. In this paper, we present a new parallelism-aware worst-case memory interference delay analysis for COTS multicore systems...
A semi-partitioned scheduler called EDF-tu is presented that is the first such scheduler to be optimal on uniform heterogeneous multiprocessors. EDF-tu utilizes an adjustable allocation parameter called a frame to schedule tasks that migrate. The frame size F must divide all task periods to ensure hard real-time optimality, but for any choice of F, maximum deadline tardiness is at most F. Thus, the...
Different task models have been proposed to represent the parallel structure of real-time tasks executing on manycore platforms: fork/join, synchronous parallel, DAG-based, etc. Despite different schedulability tests and resource augmentation bounds are available for these task systems, we experience difficulties in applying such results to real application scenarios, where the execution flow of parallel...
The sporadic DAG task model exposes parallelism that may exist within individual tasks to the run-time scheduling mechanism, and is therefore considered a particularly suitable model for representing recurrent real-time tasks that are to be implemented upon multiprocessor platforms. This paper proposes and evaluates an extension to the model to allow for the concurrent modeling of conditional execution...
In this paper we address the problem of computing the probability response time distribution of periodic tasks scheduled on a uniprocessor systems. Our framework assumes an arbitrary non-idling preemptive scheduling policy that may be either a fixed-priority scheduler (such as Rate Monotonic - RM) or a dynamic-priority scheduler (such as Earliest Deadline First - EDF). At the same time, our framework...
We focus on the problem of computing tight deadline miss models for real-time systems, which bound the number of potential deadline misses in a given sequence of activations of a task. In practical applications, such guarantees are often sufficient because many systems are in fact not hard real-time. Our major contribution is a general formulation of that problem in the context of systems where some...
To move mixed criticality research into industrial practice requires models whose run-time behaviour is acceptable to systems engineers. Certain aspects of current models, such as abandoning lower criticality tasks when certain situations arise, do not give the robustness required in application domains such as the automotive and aerospace industries. In this paper a new bailout protocol is developed...
The fast evolution of multicore systems, combined with the need of sharing the same platform for independently developed software, demands for new methodologies and algorithms that allow resource partitioning, while guaranteeing the isolation of concurrent applications. Unfortunately, a major problem that can break the isolation property of concurrent partitions is resource sharing. Although a number...
Deciding the feasibility of a sporadic task system on a preemptive uniprocessor is a central problem in real-time scheduling theory. The computational complexity of this problem has been a long-standing open question. We show that it is coNP-complete in the strong sense, even when deadlines are constrained. This is achieved by means of a pseudo-polynomial transformation from the strongly NP-hard Simultaneous...
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