Selecting Benchmarks Combinations for the Evaluation of Multicore Throughput

Most high-performance processors today are able to execute multiple threads of execution simultaneously. Threads share processor resources, like the last-level cache, which may decrease throughput in a non obvious way, depending on threads characteristics. Computer architects usually study multiprogrammed workloads by considering a set of benchmarks and some combinations of these benchmarks. Because cycle-accurate microarchitecture simulators are slow, we want a set of combinations that is as small as possible, yet representative. However, there is no standard method for selecting such sample, and different authors have used different methods. It is not clear how the choice of a particular sample impacts the conclusions of a study. We propose and compare different sampling methods for defining multiprogrammed workloads for computer architecture. We evaluate their effectiveness on a case study, the comparison of several multicore last-level cache replacement policies. We show that random sampling, the simplest method, is robust to define a representative sample of workloads, provided the sample is big enough. We propose a method for estimating the required sample size based on fast approximate simulation. We propose a new method, workload stratification, which is very effective at reducing the sample size in situations where random sampling would require large samples.Aujourd'hui, la plupart des processeurs hautes performances sont capables d'exécuter plusieurs flots d'exécution simultanément. Ces flots d'exécution partagent les ressources du processeur, comme le cache de dernier niveau, ce qui peut réduire le débit d'exécution de manière difficilement prévisible, selon les caractéristiques de ces flots. Les architectes étudient généralement les charges multitâches en considérant un ensemble de charges de référence et des combinaisons de ces charges de référence. Comme les simulateurs précis au cycle près sont lents, nous voulons un ensemble de combinaisons qui soit aussi petit que possible, mais représentatif. Cependant, il n'existe pas de méthode standard pour la sélection de ces échantillons et différents auteurs ont utilisé différentes méthodes. Il n'est pas clair en quoi le choix d'un échantillon en particulier a une incidence sur les conclusions d'une étude. Nous proposons et comparons différentes méthodes d'échantillonnage permettant de définir des charges multitâches pour l'architecture des ordinateurs. Nous évaluons leur efficacité sur une étude de cas : la comparaison de plusieurs politiques de remplacement pour le cache de dernier niveau. Nous montrons que l'échantillonnage aléatoire, la méthode la plus simple, est robuste pour définir un échantillon représentatif de la charge de travail, à condition que l'échantillon soit assez grand. Nous proposons une méthode d'estimation de la taille de l'échantillon nécessaire basée sur une simulation rapide approximative. Nous proposons une nouvelle méthode, la stratification de charges multitâches, qui est très efficace pour réduire la taille de l'échantillon dans les cas où un échantillonnage aléatoire requerrait de grands échantillons

BADCO: Behavioral Application-Dependent superscalar Core Models

Microarchitecture research and development relies heavily on simulators. The ideal simulator should be simple and easy to develop, it should be precise, accurate and very fast. As the ideal simulator does not exist, microarchitects use different sorts of simulators at different stages of the development of a processor, depending on which is most important, accuracy or simulation speed. Approximate microarchitecture models, which trade accuracy for simulation speed, are very useful for research and design space exploration, provided the loss of accuracy remains acceptable. Behavioral superscalar core modeling is a possible way to trade accuracy for simulation speed in situations where the focus of the study is not the core itself. In this approach, a superscalar core is viewed as a black box emitting requests to the uncore at certain times. A behavioral core model can be connected to a cycle-accurate uncore model. Behavioral core models are built from detailed simulations. Once the time to build the model is amortized, important simulation speedups can be obtained. We describe and study a new method for defining behavioral models for modern superscalar cores. The proposed Behavioral Application-Dependent superscalar COre model (BADCO) predicts the execution time of a thread running on a superscalar core with an error typically under 5%. We show that BADCO is qualitatively accurate, being able to predict how performance changes when we change the uncore. The simulation speedups obtained with BADCO are typically greater than 10.La recherche et développement en microarchitecture est en grande partie basée sur l'utilisation de simulateurs. Le simulateur idéal devrait être simple, facile à développer, précis, et très rapide. Comme le simulateur idéal n'existe pas, les microarchitectes utilisent différentes sortes de simulateurs à différentes étapes du développement d'un processeur, en fonction de ce qui est le plus important, la précision ou la vitesse de simulation. Les modèles approchés de microarchitecture, qui sacrifient de la précision afin d'obtenir une plus grande vitesse de simulation, sont très utiles pour la recherche et pour l'exploration d'un espace de conception, pourvu que la perte de précision reste acceptable. La modélisation comportementale de coeur superscalaire est une méthode possible de définition de modèle approché dans les cas où l'objet de l'étude n'est pas le coeur lui-même. Cette méthode considère un coeur superscalaire comme une boite noire émettant des requêtes vers le reste du processeur à des instants déterminés. Un modèle comportemental de coeur peut être connecté à un modèle de hiérarchie mémoire précis au cycle près. Les modèles comportementaux sont construits à partir de simulations détaillées. Une fois le temps de construction du modèle amorti, des gains importants en temps de simulation peuvent être obtenus. Nous décrivons et étudions une nouvelle méthode pour la définition de modèles comportementaux de coeurs superscalaires. La méthode que nous proposons, BADCO, prédit le temps d'exécution d'un programme sur un coeur superscalaire avec une erreur typiquement inférieure à 5%. Nous montrons que la précision d'un modèle BADCO est aussi qualitative et permet de prédire comment la performance change lorsqu'on modifie la hiérarchie mémoire. Les gains en temps de simulation obtenus avec BADCO sont typiquement supérieurs à 10

BADCO: Behavioral Application-Dependent Superscalar Core Models

International audienceMicroarchitecture research and development rely heavily on simulators. The ideal simulator should be simple and easy to develop, it should be precise, accurate and very fast. But the ideal simulator does not exist, and microarchitects use different sorts of simulators at different stages of the development of a processor, depending on which is most important, accuracy or simulation speed. Approximate microarchitecture models, which trade accuracy for simulation speed, are very useful for research and design space exploration, provided the loss of accuracy remains acceptable. Behavioral superscalar core modeling is a possible way to trade accuracy for simulation speed in situations where the focus of the study is not the core itself. In this approach, a superscalar core is viewed as a black box emitting requests to the uncore at certain times. A behavioral core model can be connected to a detailed uncore model. Behavioral core models are built from detailed simulations. Once the time to build the model is amortized, important simulation speedups can be obtained. We describe and study a new method for defining behavioral models for modern superscalar cores. The proposed Behavioral Application-Dependent Superscalar Core model, BADCO, predicts the execution time of a thread running on a superscalar core with an error less than 10% in most cases. We show that BADCO is qualitatively accurate, being able to predict how performance changes when we change the uncore. The simulation speedups we obtained are typically between one and two orders of magnitude

Organization and activities of school health services among EU countries

BACKGROUND: School health services (SHS) can be defined as health services provided to enrol pupils by health professionals and/or allied professions. The aim of this study was to explore the current state of the governance, organization and workforce of SHS and their provision of preventive activities in European countries. METHODS: Observational study. Data were collected as part of the Horizon 2020-funded project 'Models of Child Health Appraised'. Only 1 expert from each of the 30 included European countries answered a closed-items questionnaire during the years 2017 and 2018. RESULTS: All countries (except Spain and the Czech Republic, which do not have formal SHS) provided school-based individual screening and health-enhancing measures. The majority performed height, weight, vision and hearing checks; some integrated other assessments of limited evidence-based effectiveness. Most countries also delivered health education and promotion activities in areas, such as sexual health, substance use and healthy nutrition. Almost all countries seemed to suffer from a shortage of school health professionals; moreover, many of these professionals had no specific training in the area of school health and prevention. CONCLUSIONS: Many EU countries need better administrative and legal support. They should promote evidence-based screening procedures and should hire and train more school health professionals. Overall, they need to adapt to the evolving health priorities of pupils, adopt a more holistic paradigm and extend their activities beyond traditional screening or vaccination procedures

How to approach and take care of minor adolescents whose situations raise ethical dilemmas? a position paper of the European academy of pediatrics

In the care of adolescents, health care providers often face situations raising ethical concerns or dilemmas, such as refusal of a treatment or hospitalization, or request of confidentiality while engaging in risky behaviors or facing unplanned pregnancy. This position paper provides concrete avenues as how to assess the adolescent's capacity for autonomous decision making, e.g. the patient's competence in a specific situation, and how to elicit informed choice or consent. To do so, professionals need to be sensitized and trained as how to assess the cognitive and socio-psychological development of the young patient. Another challenge for the health professionals is to balance the needs to support patient's autonomy while offering secure guidance and protection if needed. To optimize such a process, they establish a climate of trust and empathy that will allow the patient to participate freely in the decision. In addition, especially when the decisions have potentially important consequences on the health and life, the professionals include, with the adolescent's permission, parents, caregivers or other significant adults, as well as they may request the opinion of other members of the health care team or expert colleagues such as ethicists

Immunosuppressive therapy after solid-organ transplantation: does the INTERMED identify patients at risk of poor adherence?

Lack of adherence to medication is a trigger of graft rejection in solid-organ transplant (SOT) recipients. This exploratory study aimed to assess whether a biopsychosocial evaluation using the INTERMED instrument before transplantation could identify SOT recipients at risk of suboptimal post-transplantation adherence to immunosuppressant drugs. We hypothesized that complex patients (INTERMED>20) might have lower medication adherence than noncomplex patients (INTERMED≤20). Each patient eligible for transplantation at the University Hospital of Lausanne, Switzerland, has to undergo a pre-transplantation psychiatric evaluation. In this context the patient was asked to participate in our study. The INTERMED was completed pre-transplantation, and adherence to immunosuppressive medication was monitored post-transplantation by electronic monitors for 12 months. The main outcome measure was the implementation and persistence to two calcineurin inhibitors, cyclosporine and tacrolimus, according to the dichotomized INTERMED score (>20 or ≤20). Among the 50 SOT recipients who completed the INTERMED, 32 entered the study. The complex (N=11) and noncomplex patients (N=21) were similar in terms of age, sex and transplanted organ. Implementation was 94.2% in noncomplex patients versus 87.8% in complex patients (non-significant p-value). Five patients were lost to follow-up: one was non-persistent, and four refused electronic monitoring. Of the four patients who refused monitoring, two were complex and withdrew early, and two were noncomplex and withdrew later in the study. Patients identified as complex pre-transplant by the INTERMED tended to deviate from their immunosuppressant regimen, but the findings were not statistically significant. Larger studies are needed to evaluate this association further, as well as the appropriateness of using a nonspecific biopsychosocial instrument such as INTERMED in highly morbid patients who have complex social and psychological characteristics