Méthodologie basée sur des membranes pour la gestion de la reconfiguration dynamique dans les systèmes embarqués parallèles

National audienceLa reconfiguration partielle et dynamique donne une nouvelle dimension pertinente et efficace à la conception des systèmes embarqués parallèles. Toutefois, en raison de la complexité de ces systèmes, assurer la cohérence et la gestion du parallélisme lors de l'exécution reste un défi majeur. Ainsi, des modèles d'architectures et des méthodologies de conception assistée sont nécessaires pour permettre la gestion efficace de la reconfiguration matérielle. Notre approche est inspirée des modèles, à base de composants, bien connus dans le monde du logiciel. Le modèle que l'on propose est basé sur des membranes enveloppant les composants du système. L'objectif est d'améliorer la productivité de conception et d'assurer la cohérence de la gestion des changements de composants virtuels réutilisables (IPs) ainsi que le changement de contexte. Ces membranes sont distribuées et optimisées dans le but de concevoir des systèmes autoadaptatifs

Membrane-based design and management methodology for parallel dynamically reconfigurable embedded systems

International audiencePartial and dynamic reconfiguration provides a relevant new dimension to design efficient parallel embedded systems. However, due to the encasing complexity of such systems, ensuring the consistency and parallelism management at runtime is still a key challenge. So architecture models and design methodology are required to allow for efficient component reuse and hardware reconfiguration management.This paper presents a distributed persistence management model and its implementation for reconfigurable multiprocessor systems on dynamically reconfigurable circuits. The proposed approach is inspired from the well-known component based models used in software applications development. Our model is based on membranes wrapping the systems components. The objective is to improve design productivity and ensure consistency by managing context switching and storage using modular distributed hardware controllers. These membranes are distributed and optimized with the aim to design self-adaptive systems by allowing dynamic changes in parallelism degree and contexts migration. Simulation and synthesis results are given to show performances and effectiveness of our methodology

NoC Design Flow for TDMA and QoS Management in a GALS Context

International audienceThis paper proposes a new approach dealing with the tedious problem of NoC guaranteed traffics according to GALS constraints impelled by the upcoming large System-on-Chips with multiclock domains. Our solution has been designed to adjust a tradeoff between synchronous and clockless asynchronous techniques. By means of smart interfaces between synchronous sub-NoCs, Quality-of-Service (QoS) for guaranteed traffic is assured over the entire chip despite clock heterogeneity. This methodology can be easily integrated in the usual NoC design flow as an extension to traditional NoC synchronous design flows. We present real implementation obtained with our tool for a 4G telecom scheme

Asymmetric Cache Coherency: Policy Modifications to Improve Multicore Performance

International audienceAsymmetric coherency is a new optimisation method for coherency policies to support non-uniform work- loads in multicore processors. Asymmetric coherency assists in load balancing a workload and this is applica- ble to SoC multicores where the applications are not evenly spread among the processors and customization of the coherency is possible. Asymmetric coherency is a policy change, and consequently our designs re- quire little or no additional hardware over an existing system. We explore two different types of asymmetric coherency policies. Our bus based asymmetric coherency policy, generated a 60% coherency cost reduction (reduction of latencies due to coherency messages) for non-shared data. Our directory based asymmetric co- herency policy, showed up to a 5.8% execution time improvement and up to a 22% improvement in average memory latency for the parallel benchmarks Sha, using a statically allocated asymmetry. Dynamically allo- cated asymmetry was found to generate further improvements in access latency, increasing the effectiveness of asymmetric coherency by up to 73.8% when compared to the static asymmetric solution

Embedded System Architecture for Mobile Augmented Reality. Sailor Assistance Case Study

International audienceWith upcoming see-through displays new kinds of applications of Augmented Reality are emerging. However this also raises questions about the design of associated embedded systems that must be lightweight and handle object positioning, heterogeneous sensors, wireless communications as well as graphic computation. This paper studies the specific case of a promising Mobile AR processor, which is different from usual graphics applications. A complete architecture is described, designed and prototyped on FPGA. It includes hard-ware/software partitioning based on the analysis of application requirements. The specification of an original and flexible coprocessor is detailed. Choices as well as optimizations of algorithms are also described. Implementation results and performance evaluation show the relevancy of the proposed approach and demonstrate a new kind of architecture focused on object processing and optimized for the AR domain

Design of multimedia processor based on metric computation

Media-processing applications, such as signal processing, 2D and 3D graphics rendering, and image compression, are the dominant workloads in many embedded systems today. The real-time constraints of those media applications have taxing demands on today's processor performances with low cost, low power and reduced design delay. To satisfy those challenges, a fast and efficient strategy consists in upgrading a low cost general purpose processor core. This approach is based on the personalization of a general RISC processor core according the target multimedia application requirements. Thus, if the extra cost is justified, the general purpose processor GPP core can be enforced with instruction level coprocessors, coarse grain dedicated hardware, ad hoc memories or new GPP cores. In this way the final design solution is tailored to the application requirements. The proposed approach is based on three main steps: the first one is the analysis of the targeted application using efficient metrics. The second step is the selection of the appropriate architecture template according to the first step results and recommendations. The third step is the architecture generation. This approach is experimented using various image and video algorithms showing its feasibility

Estimations et métriques au niveau système pour la conception conjointe logiciel/matériel

Cet article s'inscrit dans le thème de l'adéquation application-architecture. La méthodologie proposée couvre les étapes hautes du flot de conception conjointe, commençant au niveau de la spécification et s'arrêtant avant l'étape de partitionnement. Le but est de fournir au concepteur et à l'étape de partitionnement des informations utiles afin de construire une architecture "ad hoc" optimisée. Ainsi les estimations sont établies sans à priori sur l'architecture cible. Les potentiels d'optimisation existants entre les fonctions sont pris en compte pour obtenir un coût global et dynamique de l'application

Lightweight reconfiguration security services for AXI-based MPSoCs

International audienceNowadays, security is a key constraint in MPSoC development as many critical and secret information can be stored and manipulated within these systems. Addressing the protection issue in an efficient way is challenging as information can leak from many points. However one strategic component of a bus-based MPSoC is the communication architecture as all information that an attacker could try to extract or modify would be visible on the bus. Thus monitoring and controlling communications allows an efficient protection of the whole system. Attacks can be detected and discarded before system corruption. In this work, we propose a lightweight solution to dynamically update hardware firewall enhancements which secure data exchanges in a bus-based MPSoC. It provides a standalone security solution for AXI-based embedded systems where no user intervention is required for security mechanisms update. An FPGA implementation demonstrates an area overhead of around 11% for the adaptive version of the hardware firewall compared to the static one

Bitstreams Repository Hierarchy for FPGA Partially Reconfigurable Systems

In this paper we present a hierarchy of bitstreams repositories for FPGA-based networked and partially reconfigurable systems. These systems target embedded systems with very scarce hardware resources taking advantage of dynamic, specific and optimized architectures. Based on FPGA integrated circuits, they require a single FPGA with a network controller and less external memories to store reconfiguration software, bitstreams and buffer pools used by today's standard communication protocols. Our measures, based on a real implementation, show that our repository hierarchy is functional and can download bitstreams with a reconfiguration speed ten times faster than known solutions

Model-based design of correct controllers for dynamically reconfigurable architectures

International audienceDynamically reconfigurable hardware has been identified as a promising solution for the design of energy efficient embedded systems. However, its adoption is limited by the costly design effort including verification and validation, which is even more complex than for non dynamically reconfigurable systems. In this paper, we propose a tool-supported formal method to automatically design a correct-by-construction control of the reconfiguration. By representing system behaviors with automata, we exploit automated algorithms to synthesize controllers that safely enforce reconfiguration strategies formulated as properties to be satisfied by control. We design generic modeling patterns for a class of reconfigurable architectures, taking into account both hardware architecture and applications, as well as relevant control objectives. We validate our approach on two case studies implemented on FPGAs