Consolidation of virtual machines to reduce energy consumption of data centers by using ballooning, sharing and swapping mechanisms

International audienceData centers have major environmental impacts due to their energy consumption and the manufacturing of equipment. They emit greenhouse gases and consume energy and resources, such as rare earth and water. Efficient computing resource management is therefore a key challenge for Cloud service providers today as they need to meet a growing demand while limiting the oversizing of their infrastructures. Mechanisms derived from virtualization, such as Virtual Machines (VMs) consolidation, are used to optimize resource management and infrastructure sizing, but economic and technical constraints can hinder their adoption. They require prior infrastructure knowledge and usage study to evaluate their potential, involve complex placement algorithms, and are sometimes difficult to implement in hypervisors. In this paper, we propose ORCA (OuR Consolidation Algorithm), a complete consolidation methodology designed to facilitate the production implementation of such mechanisms. This methodology includes the study of VM usage, the use of prediction models, and a VM placement algorithm that takes advantage of resource oversubscription. The choice of relevant oversubscription ratios is also addressed, with a focus on memory overcommitment through the study of memory overcommitment mechanisms:ballooning, page sharing, and swapping. Results from a detailed simulation process and deployment on a production infrastructure are presented. The methodology is tested in simulation on two production infrastructure datasets, with power consumption reduction as high as 29.8% and without consolidation error. The production deployment using VMWare vSphere and considering fault tolerance requirements reduces the energy consumption by 6.12% without causing any performance degradation

Exact Minimum Cuts in Hypergraphs at Scale

International audienceThe hypergraph minimum cut problem aims to partition the vertices of a hypergraph into two non-empty parts while minimizing the total weight of hyperedges crossing the cut. This problem lies at the core of many tasks in network reliability, VLSI placement, and community detection. We introduce HeiCut, the first algorithm that makes exact minimum cut computation feasible for both weighted and unweighted instances at scales of hundreds of millions of vertices. HeiCut presents seven exact reduction rules that provably preserve the minimum cut, and an optional heuristic contraction based on label propagation that shrinks complex and persistent structures. When no further reductions are possible, the remaining in stance is solved exactly with a known algorithm. Our extensive evaluation on more than 500 real-world hypergraphs reveals that the exact reductions alone already expose the minimum cut (i.e., the residual collapses to a single vertex or has no hyperedges) in over 85% of instances. Across all instances, HeiCut solves over twice as many instances as the state-of-the-art within set computational limits, and is up to five orders of magnitude faster. Thus, HeiCut significantly advances hyper graph minimum cut computation in real-world, large-scale scenarios

Introduction

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Point de vue (Anthropologie)

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Evaluation of global biotic resource consumption against absolute boundaries

International audienceHuman activities rely on biotic natural resources to provide products and services necessary to meet human needs. This instrumental value is captured in life-cycle assessment through the “Natural resources” Area of Protection. Although several absolute boundaries have been proposed to safeguard biotic resources, it remains unclear whether these resources are currently used at a sustainable rate. This study addresses this question by evaluating global biotic resource consumption from 1995 to 2011 against suggested biotic resource boundaries, relying on Exiobase projections to assess the evolution beyond 2011. The assessment couples absolute boundaries with life-cycle impact assessment (LCIA) methods, enabling evaluation using consistent LCIA metrics. Five absolute boundaries and four LCIA methods were adapted to the Exiobase multiregional input-output model. Results show that most of existing boundaries are already transgressed, regardless of whether mass-based or LCIA-based control variables are applied. The wide range and normative nature of existing boundaries emphasize the need for harmonized, science-based boundaries to ensure the sustainable use of biotic resources

Orientation of nitration in bay-region of benzothioxanthene imide: A streamlined pathway to N- and S-annulated derivatives

International audienceN-annulation has recently emerged as a powerful approach for modulating the optoelectronic properties of benzothioxanthene imide (BTI) derivatives, enabling their application in areas ranging from light-emitting devices to photodynamic therapy. In this study, we report an optimized synthetic strategy that reduces the original seven-step process for N-annulated BTIs to just four steps, achieving a ~40 % improvement in efficiency. Additionally, we introduce a novel S-annulated BTI derivative, extending the scope of heteroatom-involving ring fusion. Comparative analysis between N-and S-annulated compounds reveals the pronounced influence of a single-atom modification on the π-conjugated system. These findings demonstrate the utility of annulation as a chemically accessible and versatile tool for finetuning molecular architectures with tailored photophysical properties

Point de vue (Aux carrefour des sémiotiques linguistique et visuelle)

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Abel Gance : en deçà, au-delà du cinéma

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