1,720,975 research outputs found
A Coherence Protocol for the Elimination of Passive Sharing in Single and Multiple Threaded Shared-Bus Shared-Memory Multiprocessors
No full textSingle-chip multiprocessors and multiple-thread architectures are becoming an affordable solution for high-performance general-purpose workstations and servers. On these machines, the workload is typically constituted of both sequential and multithreaded applications. Shared-bus shared-memory multithreaded multiprocessor can be used to speed-up the execution of such workload. In this environment, the scheduler takes care of the load balancing by allocating a ready thread on the first available processor, thus producing thread migration. Thread migration and the persistence of private data into different caches produce an undesired sharing, named passive sharing. The copies due to passive sharing produce useless coherence traffic on the bus and coping with such a problem may represent a challenging design problem for these machines. Many protocols use smart solutions to limit the overhead to maintain coherence among shared copies. None of these studies treats passive-sharing directly, although some indirect effect is present while dealing with the other kinds of sharing. Affinity scheduling can alleviate this problem, but this technique does not adapt to all load conditions, especially when the effects of migration are massive. A simple coherence protocol is presented. This protocol eliminates passive sharing using information from the compiler that is normally available in operating system kernels. The performance of this protocol has been evaluated and compared against other solutions proposed in the literature by means of enhanced trace-driven simulation. The performance of the proposed solution outperforms the other protocols, especially in the case of a multithreaded processor, thus demonstrating its effectiveness both in single and multiple-threaded hardware platform. The complexity of the proposed approach has been evaluated in terms of the number of protocol state
Bus Utilization Analysis of Multithreaded Shared-Bus Multiprocessors
No full textA shared-bus shared-memory system based on multithreaded processors is evaluated against different solutions for cache, processor scheduling, and coherence protocols. Multithreaded architectures have been intensively studied for DSM multiprocessors, where latencies are a major factor in limiting performance, but may be interesting also for bus-based multiprocessors, since processor speed are increasing at a much faster rate than memory. In these systems, not only pure parallel workloads, but also general workloads (i.e. constituted of both parallel and sequential applications) are the typical object of user demand for computational power. On these machines, load balancing may easily cause process migration sharing. Taking in mind also that problem, the aim of this work is therefore to investigate the relations among this kind of workloads, multithreaded processors, shared-bus architecture and coherence schemes and thereby the consequences on performance
An approach for investigating design and tuning performance of embedded systems
No full textShowing the internal behavior of a computer and the didactic path which conducts to the final design of an embedded system is often a difficult task, without adequate tools. Classical approaches may skip details of the underlaying architecture which can be fundamental to meet particular timing or consumption requirements. We propose an approach based on an environment which allows a high level of detail to be simulated, including cache, memory and I/O subsystem
MEDEA '09: Proc. 2009 workshop on MEmory performance
No full textMEDEA is a half day workshop that wants to be a forum for academic and industrial people to exchange ideas and experience on memory architectures for general-purpose, commercial and embedded systems. Main topics are memory architecture and memory-related performance/power issues, as well as memory management and optimization themes, considering system architecture and application domain in a joint manner. The program presents works on memory organization, performance and power in various kinds of systems (e.g. vector and heterogeneous CMP), and works on memory management on CMP architectures
Some Considerations About Passive Sharing in Shared-Memory Multiprocessors
No full textIn a multiprocessor system, process migration guarantees load balance between processors but causes passive sharin
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
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