Estudo da efetividade dos mecanismos de compartilhamento de memória em hipervisores

The growing demand for large-scale virtualization environments, such as the ones used in cloud computing, has led to a need for efficient management of computing resources. RAM memory is the one of the most required resources in these environments, and is usually the main factor limiting the number of virtual machines that can run on the physical host. Recently, hypervisors have brought mechanisms for transparent memory sharing between virtual machines in order to reduce the total demand for system memory. These mechanisms “merge” similar pages detected in multiple virtual machines into the same physical memory, using a copy-on-write mechanism in a manner that is transparent to the guest systems. The objective of this study is to present an overview of these mechanisms and also evaluate their performance and effectiveness. The results of two popular hypervisors (VMware and KVM) using different guest operating systems (Linux and Windows) and different workloads (synthetic and real) are presented herein. The results show significant performance differences between hypervisors according to the guest system workloads and execution time.

Avaliação de características que influenciam nos votos de utilidade de opiniões sobre serviços em português

The large number of opinions generated by online users made the former “word of mouth” find its way to virtual world. In addition to be numerous, many of the useful reviews are mixed with a large number of fraudulent, incomplete or duplicate reviews. However, how to find the features that influence on the number of votes received by an opinion and find useful reviews? The literature on opinion mining has several studies and techniques that are able to analyze of properties found in the text of reviews. This paper presents the application of a methodology for evaluation of usefulness of opinions with the aim of identifying which characteristics have more influence on the amount of votes: basic utility (e.g. ratings about the product and/or service, date of publication), textual (e.g.size of words, paragraphs) and semantics (e.g., the meaning of the words of the text). The evaluation was performed in a database extracted from TripAdvisor with opinionsabout hotels written in Portuguese. Results show that users give more attention to recent opinions with higher scores for value and location of the hotel and with lowest scores for sleep quality and service and cleanliness. Texts with positive opinions, small words, few adjectives and adverbs increase the chances of receiving more votes.