Packing Sporadic Real-Time Tasks on Identical Multiprocessor Systems

In real-time systems, in addition to the functional correctness recurrent tasks must fulfill timing constraints to ensure the correct behavior of the system. Partitioned scheduling is widely used in real-time systems, i.e., the tasks are statically assigned onto processors while ensuring that all timing constraints are met. The decision version of the problem, which is to check whether the deadline constraints of tasks can be satisfied on a given number of identical processors, has been known ${\cal NP}$-complete in the strong sense. Several studies on this problem are based on approximations involving resource augmentation, i.e., speeding up individual processors. This paper studies another type of resource augmentation by allocating additional processors, a topic that has not been explored until recently. We provide polynomial-time algorithms and analysis, in which the approximation factors are dependent upon the input instances. Specifically, the factors are related to the maximum ratio of the period to the relative deadline of a task in the given task set. We also show that these algorithms unfortunately cannot achieve a constant approximation factor for general cases. Furthermore, we prove that the problem does not admit any asymptotic polynomial-time approximation scheme (APTAS) unless ${\cal P}={\cal NP}$ when the task set has constrained deadlines, i.e., the relative deadline of a task is no more than the period of the task.Comment: Accepted and to appear in ISAAC 2018, Yi-Lan, Taiwa

Review of different approaches for optimal performance of multi-processors

We reviewed the literature used for optimal performance of multi-processor, we study different approaches in this paper. They include rate monotonic, deadline monotonic, and Earliest deadline first Algorithm. These approaches are basically used for real time scheduling systems .The problem of inconsistencies occurring in these algorithms such as those tasks whose task period is less but if not executed does not matter and whenever they are scheduled under rate monotonic scheduling algorithm the time consumed by CPU in scheduling the tasks is spent unnecessarily

Robust Partitioned Scheduling for Static-Priority Real-Time Multiprocessor Systems with Shared Resources

International audienceWe focus on the partitioned scheduling of sporadic real-time tasks with constrained deadlines. The scheduling policy on each processor is static-priority. The considered tasks are not independent and the consistency of these shared data is ensured by a multiprocessor synchronization protocol. Considering these assumptions, we propose a partitioned scheduling algorithm which tends to maximize the robustness of the tasks to the Worst Case Execution Time (WCET) overruns faults. We describe the context of the problem and we outline our solution based on simulated annealing

The Multy Supply Function Abstraction for Multiprocessors

Multi-core platforms are becoming the dominant computing architecture for next generation embedded systems. Nevertheless, designing, programming, and analyzing such systems is not easy and a solid methodology is still missing. In this paper, we propose two powerful abstractions to model the computing power of a parallel machine, which provide a general interface for developing and analyzing real-time applications in isolation, independently of the physical platform. The proposed abstractions can be applied on top of different types of service mechanisms, such as periodic servers, static partitions, and P-fair time partitions. In addition, we developed the schedulability analysis of a set of real-time tasks on top of a parallel machine that is compliant with the proposed abstractions

Real Time Event Management and Coordinating System

Analysis and prediction of real time event managing is very important and interesting as this helps experts in managing events , making decisions and working more efficiently . This thesis Event Managing And Coordinating system (RT-EMaCS) model is initially considered for proper managing of time and task, and resulted in funtioning in both system field as well as practical world. A EMaCS model can fit into any Java based platform such as laptops, desktops and any mobile device supporting Java, specially like android phones or tablets. The link between them can be done via Wi-Fi. In this thesis, the event organizers and the event coordinators communcate with better facilities in event management. It provides an easy, simple and better means of communication among one another. It prevents loss of time

Reservation-Based Federated Scheduling for Parallel Real-Time Tasks

This paper considers the scheduling of parallel real-time tasks with arbitrary-deadlines. Each job of a parallel task is described as a directed acyclic graph (DAG). In contrast to prior work in this area, where decomposition-based scheduling algorithms are proposed based on the DAG-structure and inter-task interference is analyzed as self-suspending behavior, this paper generalizes the federated scheduling approach. We propose a reservation-based algorithm, called reservation-based federated scheduling, that dominates federated scheduling. We provide general constraints for the design of such systems and prove that reservation-based federated scheduling has a constant speedup factor with respect to any optimal DAG task scheduler. Furthermore, the presented algorithm can be used in conjunction with any scheduler and scheduling analysis suitable for ordinary arbitrary-deadline sporadic task sets, i.e., without parallelism

Power-Aware Real-Time Scheduling upon Identical Multiprocessor Platforms

In this paper, we address the power-aware scheduling of sporadic constrained-deadline hard real-time tasks using dynamic voltage scaling upon multiprocessor platforms. We propose two distinct algorithms. Our first algorithm is an off-line speed determination mechanism which provides an identical speed for each processor. That speed guarantees that all deadlines are met if the jobs are scheduled using EDF. The second algorithm is an on-line and adaptive speed adjustment mechanism which reduces the energy consumption while the system is running.Comment: The manuscript corresponds to the final version of SUTC 2008 conferenc