Jean-Yves Mignolet

Architecture exploration for a reconfigurable architecture template

Coarse-grained architectures (CGRAs) can be tailored and optimized for different application domains. The vast design space of coarse-grained reconfigurable architectures complicates the design of optimized processors. The goal is to design a domain-specific processor that provides just enough-flexibility for that domain while minimizing the energy consumption for a given level of performance. However, a flexible architecture template and a retargetable simulator and compiler enable systematic architecture exploration that can lead to more efficient domain-specific architecture design. This article presents such an environment and an architecture exploration for a novel CGRA template.

Infrastructure for Design and Management of Relocatable Tasks in a Heterogeneous Reconfigurable System-on-Chip

The ability to (re)schedule a task either in hardware or software will be an important asset in a reconfigurable systems-on-chip. To support this feature we have developed an infrastructure that, combined with a suitable design environment permits the implementation and management of hardware/software relocatable tasks. This paper presents the general scope of our research, and details the communication scheme, the design environment and the hardware/software context switching issues. The infrastructure proved its feasibility by allowing us to design a relocatable video decoder. When implemented on an embedded platform, the decoder performs at 23 frames/s (320/spl times/240 pixels, 16 bits per pixel) in reconfigurable hardware and 6 frames/s in software.

Centralized Run-Time Resource Management in a Network-on-Chip Containing Reconfigurable Hardware Tiles

Run-time management of both communication and computation resources in a heterogeneous network-on-chip (NoC) is a challenging task. First, platform resources need to be assigned in a fast and efficient way. Secondly, the resources might need to be reallocated when platform conditions or user requirements change. We developed a run-time resource management scheme that is able to efficiently manage a NoC containing fine grain reconfigurable hardware tiles. This paper details our task assignment heuristic and two run-time task migration mechanisms that deal with the message consistency problem in a NoC. We show that specific reconfigurable hardware support improves the performance of the heuristic and that task migration mechanisms need to be tailored to on-chip networks.

Operating-system controlled network on chip

Managing a Network-on-Chip (NoC) in an efficient way is a challenging task. To succeed, the operating system (OS) needs to be tuned to the capabilities and the needs of the NoC. Only by creating a tight interaction can we combine the necessary flexibility with the required efficiency. This paper illustrates such an interaction by detailing the management of communication resources in a system containing a packet-switched NoC and a closely integrated OS. Our NoC system is emulated by linking an FPGA to a PDA. We show that, with the right NoC support, the OS is able to optimize communication resource usage. Additionally, the OS is able to diminish or remove the interference between independent applications sharing a common NoC communication resource.

Highly scalable network on chip for reconfigurable systems

An efficient methodology for building the billion-transistors systems on chip of tomorrow is a necessity. Networks on chip promise to be the solution for the numerous technological, economical and productivity problems. We believe that different types of networks are required for each application domains. Our approach therefore is to have a very flexible network design, highly scalable, that allows to easily accommodate the various needs. This paper presents the design of our network on chip, which is part of the platform we are developing for reconfigurable systems. The present design allows us to instantiate arbitrary network topologies, has a low latency and high throughput.

Run-time support for heterogeneous multitasking on reconfigurable SoCs

In complex reconfigurable systems on chip (SoC), the dynamism of applications requires an efficient management of the platform. To allow run-time management of heterogeneous resources, operating systems (OS) and reconfigurable SoC platforms should be developed together. For run-time support of reconfigurable architectures, the OS must abstract the reconfigurable computing resources and provide an efficient communication layer. This paper presents our efforts to simultaneously develop the run-time support and the communication layer of reconfigurable SoCs. We show that networks-on-chip (NoC) are an ideal communication layer for dynamically reconfigurable SoCs, explain how our OS provides run-time support for dynamic task relocation and detail how hardware parts of the OS are integrated into the higher layers of the NoC. An implementation of the OS and of the dedicated communication layer on our reconfigurable architecture supports the concepts we describe.

Low Cost Task Migration Initiation in a Heterogeneous MP-SoC

Run-time task migration in a heterogeneous multiprocessor system-on-chip (MP-SoC) is a challenge that requires cooperation between the task and the operating system. In task migration, minimization of the overhead during normal task execution (i.e., when not migrating) and the minimization of the migration reaction time are important. We introduce a novel technique that reuses the processors debug registers in order to minimize the overhead during normal execution. This paper explains our task migration proof-of-concept setup and compares it to the state-of-the art. By reusing existing hardware and software functionality our approach reduces the run time overhead.

MPA: Parallelizing an Application onto a Multicore Platform Made Easy

Commercial multicore platforms offer flexibility, computational power, and energy efficiency. However, a key open issue remains: how can designers quickly and efficiently map an application onto such a platform while profiting from the potential benefits? This article presents a tool to parallelize applications for execution on embedded multicore platforms, allowing fast design space exploration.

Mapping control-intensive video kernels onto a coarse-grain reconfigurable architecture: the H.264/AVC deblocking filter

Deblocking filtering represents one of the most compute intensive tasks in an H.264/AVC standard video decoder due to its demanding memory accesses and irregular data flow. For these reasons, an efficient implementation poses big challenges, especially for programmable platforms. In this sense, the mapping of this decoders functionality onto a C-programmable coarse-grained reconfigurable architecture named ADRES (architecture for dynamically reconfigurable embedded systems) is presented in this paper, including results from the evaluation of different topologies. The results obtained show a considerable reduction in the number of cycles and memory accesses needed to perform the filtering as well as an increase in the degree of instruction parallelism (ILP) when compared with an implementation on a very long instruction word (VLIW) dedicated processor. This demonstrates that high ILP is achievable on the ADRES even for irregular, data-dependent kernels

Centralized end-to-end flow control in a best-effort network-on-chip

Run-time communication management in a Network-on-Chip (NoC) is a challenging task. On one hand, the NoC needs to satisfy the communication requirements (e.g. throughput) of running applications competing for NoC resources. On the other hand, the NoC resources should be managed efficiently while keeping additional management functionalities minimal. This paper details a NoC communication management scheme based on a centralized, end-to-end flow control mechanism deployed in a best-effort NoC. This scheme comes at a very low resource (i.e. limited hardware and run-time overhead) cost. We show that by using a flow control mechanism it is possible, even in a best-effort NoC, to provide sufficient communication guarantees with respect to the application requirements. Finally, we illustrate the applicability of our approach for real-life multimedia applications.