Cache-aware static scheduling for hard real-time multicore systems based on communication affinities

The growing need for continuous processing capabilities has led to the development of multicore systems with a complex cache hierarchy. Such multicore systems are generally designed for improving the performance in average case, while hard real-time systems must consider worst-case scenarios. An open challenge is therefore to efficiently schedule hard real-time tasks on a multicore architecture. In this work, we propose a mathematical formulation for computing a static scheduling that minimize L1 data cache misses between hard real-time tasks on a multicore architecture using communication affinities

Designing a fuzzy scheduler for hard real-time systems

In hard real-time systems, tasks have to be performed not only correctly, but also in a timely fashion. If timing constraints are not met, there might be severe consequences. Task scheduling is the most important problem in designing a hard real-time system, because the scheduling algorithm ensures that tasks meet their deadlines. However, the inherent nature of uncertainty in dynamic hard real-time systems increases the problems inherent in scheduling. In an effort to alleviate these problems, we have developed a fuzzy scheduler to facilitate searching for a feasible schedule. A set of fuzzy rules are proposed to guide the search. The situation we are trying to address is the performance of the system when no feasible solution can be found, and therefore, certain tasks will not be executed. We wish to limit the number of important tasks that are not scheduled

Hierarchical Scheduling for Real-Time Periodic Tasks in Symmetric Multiprocessing

In this paper, we present a new hierarchical scheduling framework for periodic tasks in symmetric multiprocessor (SMP) platforms. Partitioned and global scheduling are the two main approaches used by SMP based systems where global scheduling is recommended for overall performance and partitioned scheduling is recommended for hard real-time performance. Our approach combines both the global and partitioned approaches of traditional SMP-based schedulers to provide hard real-time performance guarantees for critical tasks and improved response times for soft real-time tasks. Implemented as part of VxWorks, the results are confirmed using a real-time benchmark application, where response times were improved for soft real-time tasks while still providing hard real-time performance

The stack resource protocol based on real time transactions

Current hard real time (HRT) kernels have their timely behaviour guaranteed at the cost of a rather restrictive use of the available resources. This makes current HRT scheduling techniques inadequate for use in a multimedia environment where one can profit by a better and more flexible use of the resources. It is shown that one can improve the flexibility and efficiency of real time kernels and a method is proposed for precise quality of service schedulability analysis of the stack resource protocol. This protocol is generalised by introducing real time transactions, which makes its use straightforward and efficient. Transactions can be refined to nested critical sections if the smallest estimation of blocking is desired. The method can be used for hard real time systems in general and for multimedia systems in particular

Evaluation and comparison of integer programming solvers for hard real-time scheduling

[EN] In order to obtain a feasible schedule of a hard real-time system, heuristic based techniques are the solution of choice. In the last few years, optimization solvers have gained attention from research communities due to their capability of handling large number of constraints. Recently, some works have used integer linear programming (ILP) for solving mono processor scheduling of real-time systems. In fact, ILP is commonly used for static scheduling of multiprocessor systems. However, two main solvers are used to solve the problem indistinctly. But, which one is the best for obtaining a schedulable system for hard real-time systems? This paper makes a comparison of two well-known optimization software packages (CPLEX and GUROBI) for the problem of finding a feasible schedule on monoprocessor hard real-time systems.This work was supported under Grant PLEC2021-007609 funded by MCIN/AEI/10.13039/501100011033 and by the "European Union NextGeneration EU/PRTR"Guasque Ortega, A.; Balbastre, P. (2022). Evaluation and comparison of integer programming solvers for hard real-time scheduling. IEICE Transactions on Information and Systems. E105-D(10):1726-1733. https://doi.org/10.1587/transinf.2022EDP707317261733E105-D1