Umberto Villano

Analyzing cloning evolution in the Linux kernel

Abstract Identifying code duplication in large multi-platform software systems is a challenging problem. This is due to a variety of reasons including the presence of high-level programming languages and structures interleaved with hardware-dependent low-level resources and assembler code, the use of GUI-based configuration scripts generating commands to compile the system, and the extremely high number of possible different configurations. This paper studies the extent and the evolution of code duplications in the Linux kernel. Linux is a large, multi-platform software system; it is based on the Open Source concept, and so there are no obstacles in discussing its implementation. In addition, it is decidedly too large to be examined manually: the current Linux kernel release (2.4.18) is about three million LOCs. Nineteen releases, from 2.4.0 to 2.4.18, were processed and analyzed, identifying code duplication among Linux subsystems by means of a metric-based approach. The obtained results support the hypothesis that the Linux system does not contain a relevant fraction of code duplication. Furthermore, code duplication tends to remain stable across releases, thus suggesting a fairly stable structure, evolving smoothly without any evidence of degradation.

An SLA-based Broker for Cloud Infrastructures

The breakthrough of Cloud comes from its service oriented perspective where everything, including the infrastructure, is provided “as a service”. This model is really attractive and convenient for both providers and consumers, as a consequence the Cloud paradigm is quickly growing and widely spreading, also in non commercial contexts. In such a scenario, we propose to incorporate some elements of volunteer computing into the Cloud paradigm through the Cloud@Home solution, involving into the mix nodes and devices provided by potentially any owners or administrators, disclosing high computational resources to contributors and also allowing to maximize their utilization. This paper presents and discusses the first step towards Cloud@Home: providing quality of service and service level agreement facilities on top of unreliable, intermittent Cloud providers. Some of the main issues and challenges of Cloud@Home, such as the monitoring, management and brokering of resources according to service level requirements are addressed through the design of a framework core architecture. All the tasks committed to the architecture’s modules and components, as well as the most relevant component interactions, are identified and discussed from both the structural and the behavioural viewpoints. Some encouraging experiments on an early implementation prototype deployed in a real testing environment are also documented in the paper.

Security as a Service Using an SLA-Based Approach via SPECS

The cloud offers attractive options to migrate corporate applications, without any implication for the corporate security manager to manage or to secure physical resources. While this ease of migration is appealing, several security issues arise: can the validity of corporate legal compliance regulations still be ensured for remote data storage? How is it possible to assess the Cloud Service Provider (CSP) ability to meet corporate security requirements? Can one monitor and enforce the agreed cloud security levels? Unfortunately, no comprehensive solutions exist for these issues. In this context, we introduce a new approach, named SPECS. It aims to offer mechanisms to specify cloud security requirements and to assess the security features offered by CSPs, and to integrate the desired security services (e.g., credential and access management) into cloud services with a Security-as-a-Service approach. Furthermore, SPECS intends to provide systematic approaches to negotiate, to monitor and to enforce the security parameters specified in Service Level Agreements (SLA), to develop and to deploy security services that are cloud SLA-aware and are implemented as an open-source Platform-as-a-Service (PaaS). This paper introduces the main concepts of SPECS.

Heterogeneous system performance prediction and analysis using PS

PS (PVM simulator), is a simulator of PVM programs which lets users conduct performance prediction and analysis of distributed applications executed in heterogeneous and network computing environments. The article describes the tool and its development environment. As a prediction tool, the PS simulator lets developers obtain extrapolated performance data by estimating the behavior that a parallel application would attain on different types of architectures from traces collected on a workstation or on a scaled down distributed environment. As an analysis tool, it lets developers collect aggregate and analytical indexes related to heterogeneous system performance (such as efficiency, throughput, response time, and individual processor utilization) or traces that can be processed offline by a variety of tools for performance visualization and analysis (such as ParaGraph). It also lets users evaluate the effect of such factors as time spent in blocks of code, processor speed, network latency, and bandwidth on the overall application performance.

The Transition from a PVM Program Simulator to a Heterogeneous System Simulator: The HeSSE Project

This paper describes HeSSE, a research project whose objective is the development of a simulator of heterogeneous systems starting from an existing simulator of PVM applications. After a discussion on the main issues involved in dealing with a wider class of applications, the devised simulator design is described. Finally, the state of the art of the project is presented.

The CloudGrid approach

Both cloud and grid are computing paradigms that manage large sets of distributed resources, and the scientific community would benefit from their convergence. This paper proposes a novel computing model, cloudgrid, able to achieve full cloud and grid integration. After presenting its three-layer architecture, the security issues involved are analyzed, proposing a solution based on fine-grained access control mechanisms and identity federation that allows cooperation and interoperability among untrusted cloud resources. The overhead introduced by the multiple-layer architecture and by the security system are measured by extensive testing on a prototype implementation, and a trade-off analysis between security and performance is presented. Highlights? Propose an integrated approach between cloud and grid paradigms. ? Describe a fully featured implementation of the above described approach. ? Describe the security issues in cloud-on-grid and grid-on-cloud. ? Description of the solution to security problems proposed in our prototype. ? Perform a full performance analysis and security-performance tradeoff analysis in our prototype.

The metaPL approach to the performance analysis of distributed software systems

This paper presents an approach to the performance analysis of distributed software systems that relies on the use of the MetaPL notation system. MetaPL is an XML-based language that can describe programs written in different distributed programming languages and environments. The possibility to include timing information in the program description promotes the use of software performance engineering techniques during software development. Moreover, MetaPL makes also possible to analyze and to tune existing code. Both options are supported by the automatic production of program views feeding an existing distributed heterogeneous systems simulator. After an overview of the architecture of the notation system, its use for performance-driven software development and for program tuning is discussed.

Performance prediction through simulation of a hybrid MPI/OpenMP application

This paper deals with the performance prediction of hybrid MPI/OpenMP code. The use of HeSSE (Heterogeneous System Simulation Environment), along with an XML-based prototype language, MetaPL, makes it possible to predict hybrid application performance in many different working conditions, e.g., without the fully developed code or in an unavailable system. After a review of hybrid programming techniques and a brief overview of the HeSSE simulation environment, the problems related to the simulation of hybrid code and to its description through trace files are dealt with. The whole application modeling and analysis cycle is presented and validated, predicting the performance of a parallel N-body code on a SMP cluster and comparing it to the timings measured on the real system.

A Simulation-Based Framework for Autonomic Web Services

A possible solution to guarantee critical requirements in Web services designs is the use of an autonomic architecture, able to auto-configure and to auto-tune. This paper presents an innovative approach for the development of self-optimizing autonomic systems for Web services architectures, based on the adoption of a simulation engine for obtaining performance predictions. MAWeS (MetaPL/HeSSE Autonomic Web Services) is a framework whose aim is to support the development of self-optimizing predictive autonomic systems for Web service architectures. It adopts a simulation-based methodology, which allows to predict system performances in different status and load conditions. The predicted results are used for a feedforward control of the system, which self-tunes before the new conditions and the subsequent performance losses are actually observed

MetaPL: A Notation System for Parallel Program Description and Performance Analysis

This paper introduces MetaPL, a notation system designed to describe parallel programs both in the direct and in the reverse software engineering cycle. MetaPL is an XML-based Tag language, and exploits XML extension capabilities to describe programs written in different programming paradigms, interaction models and programming languages. The possibility to include timing information in the program description promotes the use of performance analysis during software development. After a description of the main features of the notation system, its use to obtain two particular program descriptions (views) is shown as an example.