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This paper deals with scheduling periodic real-time tasks on reconfigurable hardware devices, such as FPGAs. Reconfigurable hardware devices are increasingly used in embedded systems. To utilize these devices also for systems with real-time constraints, predictable task scheduling is required. We formalize the periodic task scheduling problem and propose two preemptive scheduling algorithms. The first is an adaption of the well-known Earliest Deadline First (EDF) technique to the FPGA execution model. Although the algorithm reveals good scheduling performance, it lacks an efficient schedulability test and requires a high number of FPGA configurations. The second algorithm uses the concept of servers that reserve area and execution time for other tasks. Tasks are successively merged into servers, which are then scheduled sequentially. While this method is inferior to the EDF-based technique regarding schedulability, it comes with a fast schedulability test and greatly reduces the number of required FPGA configurations.

This paper presents a prototype system that executes a set of periodic real-time tasks utilizing dynamic hardware reconfiguration. The proposed scheduling technique, MSDL, is not only able to give an offline guarantee for the feasibility of the task set but also minimizes the number of device configurations. After describing this technique, we extend the schedulability analysis to include different runtime system overheads, including the device reconfiguration time. Then we detail a light-weight runtime system that performs the online part of the MSDL scheduling technique. The runtime system is entirely implemented in hardware. Finally, we outline the corresponding synthesis tool flow and report on the overhead posed by the runtime system.

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This paper presents the architecture of an operating system (called NanoOS) for applications distributed over mobile ad hoc networks (MANETs). Furthermore, a service distribution method inspired on the foraging behavior of ants is proposed.The NanoOS offers an uniform environment of execution where the movement of nodes is transparent to the tasks. Moreover, the code of the O S is distributed among the nodes i n order to support complex services while keeping the footprint small on each node. We propose a swarm optimization based heuristic to control the migration of the O S (and application) services i n order to reduce the communication overhead. Each service request leaves pheromone i n the nodes within its path to the service provider. A n optimization step occurs when the service provider migrates to the neighbor node with the higher pheromone concentration.Realized simulations have shown that our heuristic performs well. The total communication cost i n average is just 40% higher than the global optimum obtained using Branch and Bound, while a random distribution of services result i n a cost about 350% higher than the optimum. Moreover, our algorithm just uses local information and has a very low computational requirement.

A prototype system that executes a set of periodic real-time tasks utilising dynamic hardware reconfiguration is presented. The proposed scheduling technique, merge server distribute load (MSDL), is not only able to give an offline guarantee for the feasibility of the task set, but also minimises the number of device configurations. After describing this technique, the schedulability analysis is extended to cover different runtime system overheads, including the device reconfiguration time. Then, a lightweight runtime system that performs the online part of the MSDL scheduling technique is detailed. The runtime system is implemented entirely in hardware. Finally, the corresponding synthesis tool flow is outlined and the overhead posed by the runtime system is reported.