Статическая проверка корректности разделения ресурсов в системах реального времени

Among issues which arise when developing software complexes for real-time systems (RTS) one should resolve common multi-task system issues of ensuring logical correctness of the system being created (preserving the integrity of informational resources, eliminating the possibility of mutual task blocking), as well as issues of ensuring dynamic correctness, specific for RTS (feasibility of the application tasks). In the long run, resolving these issues is reduced to checking the correctness of how synchronizing operators which ensure consistent execution of application tasks are scattered in the task bodies. In order to perform such checking statically, models which represent the scattering of synchronizing operators in application tasks are constructed. In this paper several methods of processing such models are proposed which are based on constructing special multi-partite graphs — graphs of synchronizing operator dependencies. Two varieties of such graphs are resented: a) graphs of bundles, which ensure verification of logical correctness of multi-task applications (correctness of intersections of critical interval pairs); and b) graphs of bundles and critical intervals, which ensure verification of dynamic correctness of RTS applications.В ряду вопросов, возникающих в ходе разработки программных комплексов для СРВ, необходимо решать как общие для многозадачных систем вопросы обеспечения логической корректности создаваемой системы (сохранение целостности информационных ресурсов, исключения возможности взаимного блокирования задач), так и специфические для СРВ вопросы динамической корректности (своевременности исполнения задач). Решение этих вопросов в конечном счете сводится к проверке корректности размещения в теле каждой из задач синхронизирующих операторов, обеспечивающих согласованное исполнение задач. Такая проверка корректности осуществляется статически. С этой целью строятся модели, отражающие размещение синхронизирующих операторов в задачах приложения. В настоящей статье предлагаются методы обработки таких моделей посредством построения специальных многодольных графов — графов зависимостей синхронизирующих операторов. Представляются две разновидности таких графов: а) графы связок, обеспечивающие проверку логической корректности многозадачных приложений, (корректность пересечений пар критических интервалов); и б) графы связок и критических интервалов, обеспечивающие проверку динамической корректности приложений для СРВ

Response-time analysis of DAG tasks supporting heterogeneous computing

Hardware platforms are evolving towards parallel and heterogeneous architectures to overcome the increasing necessity of more performance in the real-time domain. Parallel programming models are fundamental to exploit the performance capabilities of these architectures. This paper proposes a novel response time analysis (RTA) for verifying the schedulability of DAG tasks supporting heterogeneous computing. It analyzes the impact of executing part of the DAG in the accelerator device. As a result, the response time upper bound of the system is more precise than the one provided by currently existing RTA targeting homogeneous architectures.This work is supported by the Spanish Ministry of Science and Innovation under contract TIN2015-65316-PPeer ReviewedPostprint (published version

Towards an OpenMP Specification for Critical Real-Time Systems

OpenMP is increasingly being considered as a convenient parallel programming model to cope with the performance requirements of critical real-time systems. Recent works demonstrate that OpenMP enables to derive guarantees on the functional and timing behavior of the system, a fundamental requirement of such systems. These works, however, focus only on the exploitation of fine grain parallelism and do not take into account the peculiarities of critical real-time systems, commonly composed of a set of concurrent functionalities. OpenMP allows exploiting the parallelism exposed within real-time tasks and among them. This paper analyzes the challenges of combining the concurrency model of real-time tasks with the parallel model of OpenMP. We demonstrate that OpenMP is suitable to develop advanced critical real-time systems by virtue of few changes on the specification, which allow the scheduling behavior desired (regarding execution priorities, preemption, migration and allocation strategies) in such systems.The research leading to these results has received funding from the Spanish Ministry of Science and Innovation, under contract TIN2015-65316-P, and from the European Union's Horizon 2020 Programme under the CLASS Project (www.classproject. eu), grant agreement No 780622.Peer ReviewedPostprint (author's final draft

Energy-Efficient Multi-Core Scheduling for Real-Time DAG Tasks

In this work, we study energy-aware real-time scheduling of a set of sporadic Directed Acyclic Graph (DAG) tasks with implicit deadlines. While meeting all real-time constraints, we try to identify the best task allocation and execution pattern such that the average power consumption of the whole platform is minimized. To the best of our knowledge, this is the first work that addresses the power consumption issue in scheduling multiple DAG tasks on multi-cores and allows intra-task processor sharing. We first adapt the decomposition-based framework for federated scheduling and propose an energy-sub-optimal scheduler. Then we derive an approximation algorithm to identify processors to be merged together for further improvements in energy-efficiency and to prove the bound of the approximation ratio. We perform a simulation study to demonstrate the effectiveness and efficiency of the proposed scheduling. The simulation results show that our algorithms achieve an energy saving of 27% to 41% compared to existing DAG task schedulers

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

The Global EDF Scheduling of Systems of Conditional Sporadic DAG Tasks

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 of pieces of an individual task, along with the modeling of intra-task parallelism. The Global Earliest Deadline First (GEDF) scheduling of systems represented in this generalized model is studied, and a GEDF-schedulability test is derived. With regards to GEDF scheduling it is shown that there is no penalty, in terms of worse speedup factor, in generalizing the sporadic DAG tasks model in this manner

The Global EDF Scheduling of Systems of Conditional Sporadic DAG Tasks

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 of pieces of an individual task, along with the modeling of intra-task parallelism. The Global Earliest Deadline First (GEDF) scheduling of systems represented in this generalized model is studied, and a GEDF-schedulability test is derived. With regards to GEDF scheduling it is shown that there is no penalty, in terms of worse speedup factor, in generalizing the sporadic DAG tasks model in this manner