386 research outputs found
WCET analysis of multi-level set-associative instruction caches
With the advent of increasingly complex hardware in real-time embedded
systems (processors with performance enhancing features such as pipelines,
cache hierarchy, multiple cores), many processors now have a set-associative L2
cache. Thus, there is a need for considering cache hierarchies when validating
the temporal behavior of real-time systems, in particular when estimating
tasks' worst-case execution times (WCETs). To the best of our knowledge, there
is only one approach for WCET estimation for systems with cache hierarchies
[Mueller, 1997], which turns out to be unsafe for set-associative caches. In
this paper, we highlight the conditions under which the approach described in
[Mueller, 1997] is unsafe. A safe static instruction cache analysis method is
then presented. Contrary to [Mueller, 1997] our method supports set-associative
and fully associative caches. The proposed method is experimented on
medium-size and large programs. We show that the method is most of the time
tight. We further show that in all cases WCET estimations are much tighter when
considering the cache hierarchy than when considering only the L1 cache. An
evaluation of the analysis time is conducted, demonstrating that analysing the
cache hierarchy has a reasonable computation time
The Heptane Static Worst-Case Execution Time Estimation Tool
Estimation of worst-case execution times (WCETs) is required to validate the temporal behavior of hard real time systems. Heptane is an open-source software program that estimates upper bounds of execution times on MIPS and ARM v7 architectures, offered to the WCET estimation community to experiment new WCET estimation techniques. The software architecture of Heptane was designed to be as modular and extensible as possible to facilitate the integration of new approaches. This paper is devoted to a description of Heptane, and includes information on the analyses it implements, how to use it and extend it
Cache-Conscious Offline Real-Time Task Scheduling for Multi-Core Processors
Most schedulability analysis techniques for multi-core architectures assume a single Worst-Case Execution Time (WCET) per task, which is valid in all execution conditions. This assumption is too pessimistic for parallel applications running on multi-core architectures with local instruction or data caches, for which the WCET of a task depends on the cache contents at the beginning of its execution, itself depending on the task that was executed before the task under study.
In this paper, we propose two scheduling techniques for multi-core architectures equipped with local instruction and data caches. The two techniques schedule a parallel application modeled as a task graph, and generate a static partitioned non-preemptive schedule. We propose an optimal method, using an Integer Linear Programming (ILP) formulation, as well as a heuristic method based on list scheduling. Experimental results show that by taking into account the effect of private caches on tasks\u27 WCETs, the length of generated schedules is significantly reduced as compared to schedules generated by cache-unaware scheduling methods. The observed schedule length reduction on streaming applications is 11% on average for the optimal method and 9% on average for the heuristic method
Association entre les caractéristiques reliées à la santé mentale maternelle et le gain de poids gestationnel dans la cohorte 3D
Introduction : Les indicateurs de santĂ© mentale (ISM) pourraient ĂȘtre des facteurs Ă©tiologiques du gain de poids gestationnel (GPG).
MĂ©thodologie : Lâobjectif de ce mĂ©moire est dâĂ©valuer lâassociation entre les ISM et le GPG chez les femmes enceintes quĂ©bĂ©coises. Une Ă©tude observationnelle de 2 204 participantes nichĂ©e dans la cohorte prospective 3D a Ă©tĂ© rĂ©alisĂ©e. Lâissue principale est le taux moyen de GPG (TGPG) aux deuxiĂšmes et troisiĂšmes trimestres en kilogrammes/semaine. Le TGPG a aussi Ă©tĂ© catĂ©gorisĂ© comme insuffisant (GPGI), adĂ©quat (GPGA) ou excessif (GPGE), selon les lignes directrices du National Academy of Medicine. AprĂšs lâimputation multiple des donnĂ©es, des modĂšles de rĂ©gression linĂ©aire et logistique multiple ont Ă©tĂ© construits afin dâĂ©valuer lâassociation entre chacun des ISM mesurĂ©s au premier et deuxiĂšme trimestre et les issues de GPG. Les analyses ont Ă©tĂ© rĂ©alisĂ©es Ă lâaide des logiciels R et SPSS, avec un seuil de significativitĂ© statistique p<0,05.
RĂ©sultats : Les antĂ©cĂ©dents de maladie psychiatrique ont Ă©tĂ© associĂ©s au TGPG (Ă= -0,055, p=0,02). Chez les participantes avec un poids insuffisant avant la grossesse, des associations statistiquement significatives ont Ă©tĂ© retrouvĂ©es entre le GPG et les expositions suivantes : le stress ressenti (TGPG, Ă= 0,067, p80 000 : GPGE, RC 1,83, p= 0,04; >80 000$ : GPGE, RC 0,72, p<0,01). Le TIT a Ă©galement Ă©tĂ© associĂ© au GPGE (RC 0,86, p=0,03). Le TNR a Ă©tĂ© associĂ© au TGPG avec une interaction statistiquement significative du sexe fĆtal (sexe masculin Ă= -0,031, p<0,01 ; sexe fĂ©minin Ă=-0,004, p=0,68). Le « travail ne nĂ©cessitant pas de crĂ©ativitĂ© » a Ă©tĂ© associĂ© au TGPG dans lâensemble de la cohorte (Ă=-0,013, p=0,04). Aucune association statistiquement significative nâa Ă©tĂ© retrouvĂ©e entre lâinsĂ©curitĂ© alimentaire, les traits anxieux, les Ă©vĂšnements de vie indĂ©sirables en grossesse, lâestime de soi, lâoptimisme et les issues de GPG.
Conclusion : Les antĂ©cĂ©dents de maladie psychiatrique, et certaines caractĂ©ristiques de stress liĂ© au travail ont Ă©tĂ© associĂ©s nĂ©gativement au TGPG dans la cohorte 3D. Chez les femmes avec un poids insuffisant en dĂ©but de grossesse, le stress, les symptĂŽmes dĂ©pressifs et les inquiĂ©tudes par rapport Ă lâabandon ont Ă©tĂ© associĂ©s positivement avec le GPG et le GPGE
Le patrimoine sur scÚne : théùtre, musée et site historique
Cette Ă©tude porte sur la pratique de mĂ©diation du patrimoine employant des personnages historiques comme mĂ©diateurs lors de performances au sein de musĂ©es et de sites historiques. Nous posons plus prĂ©cisĂ©ment notre regard sur Dramamuse, lâancienne troupe de thĂ©Ăątre du MusĂ©e canadien des civilisations Ă Gatineau, et sur le service dâanimation du site historique des plaines dâAbraham Ă QuĂ©bec. Nous examinons la dimension pratique de leurs diffĂ©rentes performances en dĂ©crivant et en analysant les Ă©lĂ©ments permettant dâinstaurer et de maintenir une relation de mĂ©diation. Nous interrogeons les rĂŽles de ces Ă©lĂ©ments, leur pertinence, leurs avantages et leurs inconvĂ©nients, etc. Nos rĂ©sultats dĂ©montrent quâune combinaison de trois piliers, Ă savoir le personnage, lâacteur et les outils que le « personnage-acteur » utilise, permet aux visiteurs de vivre une expĂ©rience cognitive, Ă©motive et sensorielle par rapport au patrimoine. Ces rĂ©sultats apportent un Ă©clairage nouveau sur cette pratique de mĂ©diation du patrimoine.This study examines the performance of historical characters as a form of heritage interpretation in museums and historic sites. We focus on Dramamuse, the former theatre company of the Canadian Museum of Civilization in Gatineau, as well as at the Animation Department of the Plains of Abraham, a historical site in Quebec City. We examine the practical dimension of their different performances by describing and analyzing the elements needed to engage with the visitors. We investigate the roles of these elements, their relevance, their advantages and disadvantages, etc. Our results show that a combination of three pillars, namely the character, the actor and the tools used by the « character-actor », create a cognitive, emotional and sensorial experience of heritage for the visitors. These results shed light on a rich and developing practice in heritage interpretation
Integrated polymers (PVCi/PMATRIFE) microring resonators for low power tunable ïŹlters
International audienceIn this paper we present optical and thermo-optical characterization results of integrated ïŹlters based on micro-ring resonators fabricated with a couple of polymers ''PVCI/PMATRIFE''. Their high index contrast (Dn 0.15 at the wavelength of 1550 nm) allows to make small size waveguides with cross sections of 1.5 1.5 mm2. The study of the impact of different gaps on the extinction ratio and FWHM (full width at half maximum) of ïŹlters leads to a better design. First experiments of thermal tunability of the microring ïŹlter using a thermo-electric cooler (TEC) are also reported giving a 5 nm shift of the dropped wavelength for a temperature change of 40 K. The fabrication of gold electrodes on microrings is reported and the electrical power required for the tuning of the drop wavelength of 0.0055 nm/1 mW show that with an optimized electrode design the consumption will be low
Stratégies de réalisation de guides polymÚres pour la modulation électro-optique à haut débit
National audienceDe nouveaux polymĂšres Ă©lectro-optiques, sont mis en Ćuvre pour rĂ©aliser des guides selon deux types d'ingĂ©nierie de matĂ©riaux. L'une consiste Ă utiliser un polymĂšre non-linĂ©aire greffĂ© et rĂ©ticulable et l'autre utilise un matĂ©riau hĂŽte, ayant une tempĂ©rature de transition vitreuse Ă©levĂ©e. Nous prĂ©sentons ici, les difficultĂ©s rencontrĂ©es lors de la rĂ©alisation des guides et les stratĂ©gies dĂ©veloppĂ©es pour aboutir, avec ces nouveaux matĂ©riaux, Ă des guides optiques monomodes
Caractérisation interférométrique du coefficient électro-optique de guides polymers intégrés
session affiches A7 " Instrumentation, Caractérisation et Capteurs " [A7.4]National audienceNous présentons ici une méthode de caractérisation de modulateurs électro-optiques en polymÚres par l'intermédiaire d'un Mach-Zehnder fibré. Les résultats obtenus par modulation de phase, dans une fibre optique soumise à des contraintes piézoélectriques, témoignent de la faisabilité de la méthode et montrent qu'une caractérisation avec une résolution satisfaisante est possible au moyen d'un procédé expérimental simple
Matériaux polymÚres pour la création de guides optiques
5 pagesNational audienceUn des objectifs de travail au laboratoire Foton est l'amĂ©lioration du confinement de la lumiĂšre dans les microstructures polymĂšres, de par leurs propriĂ©tĂ©s optiques (indices de rĂ©fraction optimisĂ©s, transparence Ă la longueur d'onde choisie) et chimiques (compatibilitĂ© des matĂ©riaux de cĆur et de gaine, stabilitĂ© dans le temps), ainsi que par la rĂ©duction des pertes intrinsĂšques et extrinsĂšques des guides. Pour cela, la dĂ©termination des propriĂ©tĂ©s physico-chimiques des polymĂšres utilisĂ©s lors de la crĂ©ation d'un guide optique et l'optimisation des interfaces mises en jeu sont deux directions de travail privilĂ©giĂ©es, sachant que les structures polymĂšres sont rĂ©alisĂ©es en photolithographie conventionnelle par masquage dans l'UV Ă 365 nm sur un substrat de silicium, suivi d'une gravure RIE
Predictable Code and Data Paging for Real Time Systems
There is a need for using virtual memory in real-time ap-plications: using virtual addressing provides isolation between concurrent processes; in addition, paging allows the execution of applications whose size is larger than main memory capac-ity, which is useful in embedded systems where main memory is expensive and thus scarce. However, virtual memory is gen-erally avoided when developing real-time and embedded appli-cations due to predictability issues. In this paper we propose a predictable paging system in which the page loading and page eviction points are selected at compile-time. The contents of main memory is selected using an Integer Linear Programming (ILP) formulation. Our approach is applied to code, static data and stack regions of individual tasks. We show that the time re-quired for selecting memory contents is reasonable for all ap-plications including the largest ones, demonstrating the scala-bility of our approach. Experimental results compare our ap-proach with a previous one, based on graph coloring. It shows that quality of page allocation is generally improved, with an average improvement of 30 % over the previous approach. An-other comparison with a state-of-the-art demand-paging sys-tem shows that predictability does not come at the price of per-formance loss. 1
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