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1

A new sufficient schedulability analysis for hybrid scheduling

Zhang F., Zhai Y., Liao J.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 3

683--692

EN

Earliest deadline first (EDF) and fixed priority (FP) are the most commonly used and studied scheduling algorithms for real-time systems. This paper focuses on combining the EDF and FP strategies in one system. We provide a new sufficient schedulability analysis for real-time hybrid task systems which are scheduled by EDF and FP. The proposed analysis has a polynomial time complexity and no restrictions on task parameters, where the relative deadline of each task could be less than, equal to, or greater than its period. By extensive experiments, we show that our proposed analysis significantly improves the acceptance ratio compared with the existing results of the sufficient schedulability test for hybrid scheduling systems.

2

Maintaining the feasibility of hard real-time systems with a reduced number of priority levels

Qureshi M. B., Alrashed S., Min-Allah N., Kołodziej J., Arabas P.

International Journal of Applied Mathematics and Computer Science

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2015

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Vol. 25, no. 4

709--722

EN

When there is a mismatch between the cardinality of a periodic task set and the priority levels supported by the underlying hardware systems, multiple tasks are grouped into one class so as to maintain a specific level of confidence in their accuracy. However, such a transformation is achieved at the expense of the loss of schedulability of the original task set. We further investigate the aforementioned problem and report the following contributions: (i) a novel technique for mapping unlimited priority tasks into a reduced number of classes that do not violate the schedulability of the original task set and (ii) an efficient feasibility test that eliminates insufficient points during the feasibility analysis. The theoretical correctness of both contributions is checked through formal verifications. Moreover, the experimental results reveal the superiority of our work over the existing feasibility tests by reducing the number of scheduling points that are needed otherwise.

3

Partition of real-time application over multicore systems

Martyna J.

Automatyka / Automatics

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2012

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Vol. 16, no. 2

127-136

EN

In this paper, we present a model of parallel execution of a real-time application in a multicore system. Currently used modern architectures provide a mechanism to prevent reciprocal inter-ference in the cause of critical activities. We propose an algorithm for obtaining the partitions of real-time applications and later for their allocation to a set of all accessible cores of a multicore pro-cessor. The algorithm takes into consideration all the constraints, such as precedence relations, timing dependencies, eta, and allows all partitions to access resources in order of their potential utility to the application. Some experimental results are provided.

PL

W artykule przedstawiono model równoległego wykonania aplikacji czasu rzeczywistego w wielordzeniowym systemie komputerowym. Współczesne komputery dostarczają mechanizmów dla równoległego wykonywania programów czasu rzeczywistego. Zaproponowano algorytm do przeprowadzenia podziału aplikacji czasu rzeczywistego na elementy składowe i ich alokacji w środowisku równoległych procesorów wielordzeniowych. Algorytm ten bierze pod uwagę wszystkie ograniczenia związane z wykonywaniem programu czasu rzeczywistego, w tym relację poprzedzania oraz zależności czasowe. Dzięki przedstawionemu rozwiązaniu jest możliwe pełne wykorzystanie mocy obliczeniowej wielordzeniowych procesorów dla wykonania aplikacji czasu rzeczywistego.