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1.
We present a technique that controls the peak power consumption of a high-density server by implementing a feedback controller
that uses precise, system-level power measurement to periodically select the highest performance state while keeping the system
within a fixed power constraint. A control theoretic methodology is applied to systematically design this control loop with
analytic assurances of system stability and controller performance, despite unpredictable workloads and running environments.
In a real server we are able to control power over a 1 second period to within 1 W and over an 8 second period to within 0.1 W.
Conventional servers respond to power supply constraint situations by using simple open-loop policies to set a safe performance
level in order to limit peak power consumption. We show that closed-loop control can provide higher performance under these
conditions and implement this technique on an IBM BladeCenter HS20 server. Experimental results demonstrate that closed-loop
control provides up to 82% higher application performance compared to open-loop control and up to 17% higher performance compared
to a widely used ad-hoc technique.
相似文献
Malcolm WareEmail: |
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VPM tokens: virtual machine-aware power budgeting in datacenters 总被引:1,自引:0,他引:1
Power consumption and cooling overheads are becoming increasingly significant for enterprise datacenters, affecting overall
costs and the ability to extend resource capacities. To help mitigate these issues, active power management technologies are
being deployed aggressively, including power budgeting, which enables improved power provisioning and can address critical
periods when power delivery or cooling capabilities are temporarily reduced. Given the use of virtualization to encapsulate
application components into virtual machines (VMs), however, such power management capabilities must address the interplay
between budgeting physical resources and the performance of the virtual machines used to run these applications. This paper
proposes a set of management components and abstractions for use by software power budgeting policies. The key idea is to
manage power from a VM-centric point of view, where the goal is to be aware of global utility tradeoffs between different
virtual machines (and their applications) when maintaining power constraints for the physical hardware on which they run.
Our approach to VM-aware power budgeting uses multiple distributed managers integrated into the VirtualPower Management (VPM)
framework whose actions are coordinated via a new abstraction, termed VPM tokens. An implementation with the Xen hypervisor
illustrates technical benefits of VPM tokens that include up to 43% improvements in global utility, highlighting the ability
to dynamically improve cluster performance while still meeting power budgets. We also demonstrate how VirtualPower based budgeting
technologies can be leveraged to improve datacenter efficiency in the context of cooling infrastructure management.
相似文献
Yogendra JoshiEmail: |
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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
相似文献
Michael S. Engel (Corresponding author)Email: |
9.
Terry Harmer 《Cluster computing》2007,10(3):277-285
Gridcast is an R&D project investigating grid ideas and technologies in the broadcasting technical infrastructure. In this
paper I discuss the business and technical issues in building infrastructures to support broadcasters and outline the structure
of the Gridcast grid-based service oriented architecture for broadcasting playout support.
相似文献
Terry HarmerEmail: |
10.
Over the last 20 years, transfer of the management of natural resources to local populations has been a major trend in the
tropics. Many of these initiatives today incorporate the development of monitoring systems based on Criteria and Indicators
(C&I), used to gauge environmental, socio-economic, and institutional consequences over a long period of time. The design
of C&I at a local level involves combining scientific expertise with traditional ecological knowledge. There are numerous
methods of merging these two branches of knowledge and developing a local monitoring system. The difficulty lies in setting
up these local monitoring systems. A review of the literature available demonstrates that the handing over of monitoring systems
to local communities has rarely been successful. In almost every case study, when the donor agency initiating the process
withdrew, monitoring was either much less intensive or came to a complete stop. Despite this blatant deficiency local monitoring
systems constitute an almost compulsory component of any donor-funded program/project dealing with sustainable management
of natural resources. In our views, the real implementation of C&I by and for communities can only be achieved if there is
a genuine devolution of management power, including responsibilities and benefits, to local stakeholders. Unless they link
environmental changes to the communities’ own management decisions, formal participative monitoring systems will continue
to fail.
相似文献
Guillaume LescuyerEmail: |
11.
Rapid prototyping of distributed systems can be achieved by integrating commercial off-the-shelf (COTS) components. With components
as the building blocks, it is important to predict the performance of the system based on the performance of individual components.
In this paper, performance prediction of a system consisting of a small number of components is investigated under different
inter-component communication patterns, and the number of threads provided by components. Based on the experimental results,
it can be inferred that the proposed composition rules provide a reasonably accurate prediction of the performance of a system
made out of these components.
相似文献
Barrett R. BryantEmail: |
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Mathematical neuronal models are normally expressed using differential equations. The Parker-Sochacki method is a new technique
for the numerical integration of differential equations applicable to many neuronal models. Using this method, the solution
order can be adapted according to the local conditions at each time step, enabling adaptive error control without changing
the integration timestep. The method has been limited to polynomial equations, but we present division and power operations
that expand its scope. We apply the Parker-Sochacki method to the Izhikevich ‘simple’ model and a Hodgkin-Huxley type neuron,
comparing the results with those obtained using the Runge-Kutta and Bulirsch-Stoer methods. Benchmark simulations demonstrate
an improved speed/accuracy trade-off for the method relative to these established techniques.
相似文献
Robert D. StewartEmail: |
14.
Summary The tree species Berlinia korupensis Mackinder & Burgt is described as new. The species is endemic to the southern part of
Korup National Park in Cameroon. Seventeen trees have been found so far, the largest being 42 m high and having a trunk diam.
of 88 cm. The new species is assessed as Critically Endangered (CR D) under the criteria of IUCN. Two distribution maps are
included; one map indicating the single locality in Cameroon near the Nigerian border where the new species was found and
another map of the permanent plot where 14 of the 17 trees were recorded. A line drawing is also included, along with colour
photographs of the flowers and the trunk.
相似文献
Barbara A. MackinderEmail: |
15.
Dispersed information diffusion with level and schema-based coordination in mobile peer to peer networks 总被引:1,自引:0,他引:1
Several open ended issues for high resource availability in mobile peer to peer networks have been examined in the recent
past. Different approaches were conducted for supporting information distribution and availability, through guided or unguided
packet diffusion. The majority of the recently proposed approaches try to benefit from the spatial characteristics of the
dynamically varying topologies. In this work a directed information diffusion scheme is examined using a level and schema-based
coordination, applied in mobile peer to peer networks. The prioritization degree of any requested advert is modeled and enables
directed prioritized diffusions to end mobile users that are traversing a certain geographic region (location based advertisements).
The proposed method is robust in disseminating redundant messages to users while maintaining connectivity through Gradual
Energy Tree-based (GET) configuration. Simulation is performed for the examination and performance evaluation of the proposed
scheme, taking into account the modeled prioritization as well as the diffusion accuracy by using the Hierarchical and Non-hierarchical
GET configuration.
相似文献
Helen D. KaratzaEmail: |
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Scheduling mixed-parallel applications with advance reservations 总被引:1,自引:0,他引:1
This paper investigates the scheduling of mixed-parallel applications, which exhibit both task and data parallelism, in advance
reservations settings. Both the problem of minimizing application turn-around time and that of meeting a deadline are studied.
For each several scheduling algorithms are proposed, some of which borrow ideas from previously published work in non-reservation
settings. Algorithms are compared in simulation over a wide range of application and reservation scenarios. The main finding
is that schedules computed using the previously published CPA algorithm can be adapted to advance reservation settings, notably
resulting in low resource consumption and thus high efficiency.
相似文献
Henri Casanova (Corresponding author)Email: |
18.
Coral reef marine protected areas (MPA) are widely distributed around the globe for social and ecological reasons. Relatively
few of these MPAs are well managed. This review examines the governance of coral reef MPAs and the means to improve coral
reef MPA management. It highlights common governance challenges, such as confused goals, conflict, and unrealistic attempts
to scale up beyond institutional capacity. Recommendations, based on field experience and empirical evidence from around the
world, are made for best practices at various stages of MPA implementation.
相似文献
A. T. WhiteEmail: |
19.
Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
20.
Anonymous communications in the Internet 总被引:1,自引:0,他引:1
Arjan Durresi 《Cluster computing》2007,10(1):57-66
With the growth and acceptance of the Internet, there has been increased interest in maintaining anonymity in the network.
By using traffic analysis, it is possible to infer who is talking to whom over the Internet. We present a novel approach to
hide the senders and the receivers of messages. Routes are chosen and frames traverse these routes. Each frame consists of
a token and a node can send a message through a frame only when the corresponding token is free. The advantage of our protocol
is that it poses limited bandwidth overhead when there is at least some traffic, while posing minimal bandwidth overhead when
there is no traffic at all.
相似文献
Arjan DurresiEmail: |