1,720,990 research outputs found
An implementation of a multiprocessor bandwidth reservation mechanism for groups of tasks
No full textA Linux-based Virtualized Solution Providing Computing Quality of Service to SDN-NFV Telecommunication Applications
No full textAn implementation of the Bandwidth Inheritance Protocol in the Linux Kernel
No full textThe Resource Reservation (RR) framework has been proven very effective in the joint scheduling of hard real time and soft real time application in Open Systems. A fundamental problem in this context concerns the extension of the Resource Reservation approach to systems where tasks interact through shared resources.
The Bandwidth Inheritance (BWI) protocol was first proposed in [Lamastra G., Lipari G., Abeni L. (2001) A bandwidth inheritance algorithm for real-time task synchronization in open systems. In: Proc. 22nd IEEE Real-Time Systems Symposium] to preserve Bandwidth Isolation between independent groups of tasks, and to enable a schedulability analysis for hard real time tasks.
In this paper, we present the first implementation of the BWI protocol within the Linux kernel. We describe the protocol, the way it has been implemented in Linux, and we report some early experiments to measure its overhead. Our work is based on the SCHED_DEADLINE patch, a scheduling class for the Linux kernel that provides Resource Reservation using the Constant Bandwidth Server algorithm. The BWI implementation extends Linux's current implementation of the Priority Inheritance protocol, without affecting past design decisions. Our implementation is neutral to the underlying scheduling scheme and can be adopted in global, clustered and partitioned scheduling.
Results show agreement with theoretical analysis, and performance/overheads comparable with the current implementation of Priority Inheritance in Linux.
The work presented here has practical implications for applications running on Linux with SCHED_DEADLINE scheduling policy and share resources through mutex semaphores. In fact, the protocol guarantees temporal isolation between non-interacting threads, hence real-time guarantees are possible even where no a-priori information about tasks' scheduling parameters are available
Response time analysis for G-EDF and G-DM scheduling of sporadic DAG-tasks with arbitrary deadline
No full textNew programming models have been proposed to exploit the parallelism of modern computing architectures. Also in the real-time domain more detailed task models are under evaluation to provide a tighter analysis of parallel application with precedence and timing constraints. This paper presents two schedulability tests based on Response Time Analysis for determining whether a set of sporadic DAG-tasks with arbitrary deadlines can be scheduled by G-EDF or G-DM on a platform consisting of m identical processor. The first test is a simple polynomial time test, while the second one is a pseudo-polynomial time test. Our tests exploit the combinatorial properties of the DAGs by considering the interference experienced by each vertex. We describe a set of simulations showing that our tests outperform the tests described in [7] in terms of schedulability ratio and running time. We also provide resource augmentation bounds for our polynomial time test when considering single-DAG systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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