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  • On the use of social trajectory-based clustering methods for public transport optimization

     Nin Guerrero, Jordi; Carrera Perez, David; Villatoro, Daniel
    Lecture notes in computer science
    Date of publication: 2014
    Journal article

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    Public transport optimisation is becoming everyday a more dicult and challenging task, because of the increasing number of transportation options as well as the exponential increase of users. Many research contributions about this issue have been recently published under the umbrella of the smart cities research. In this work, we sketch a possible framework to optimize the tourist bus in the city of Barcelona. Our framework will extract information from Twitter and other web services, such as Foursquare to infer not only the most visited places in Barcelona, but also the trajectories and routes that tourist follow. After that, instead of using complex geospatial or trajectory clustering methods, we propose to use simpler clustering techniques as k-means or DBScan but using a real sequence of symbols as a distance measure to incorporate in the clustering process the trajectory information.

  • Deadline-based MapReduce workload management

     Polo, Jorda; Becerra Fontal, Yolanda; Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    IEEE transactions on network and service management
    Date of publication: 2013
    Journal article

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    This paper presents a scheduling technique for multi-job MapReduce workloads that is able to dynamically build performance models of the executing workloads, and then use these models for scheduling purposes. This ability is leveraged to adaptively manage workload performance while observing and taking advantage of the particulars of the execution environment of modern data analytics applications, such as hardware heterogeneity and distributed storage. The technique targets a highly dynamic environment in which new jobs can be submitted at any time, and in which MapReduce workloads share physical resources with other workloads. Thus the actual amount of resources available for applications can vary over time. Beyond the formulation of the problem and the description of the algorithm and technique, a working prototype (called Adaptive Scheduler) has been implemented. Using the prototype and medium-sized clusters (of the order of tens of nodes), the following aspects have been studied separately: the scheduler's ability to meet high-level performance goals guided only by user-defined completion time goals; the scheduler's ability to favor data-locality in the scheduling algorithm; and the scheduler's ability to deal with hardware heterogeneity, which introduces hardware affinity and relative performance characterization for those applications that can benefit from executing on specialized processors.

  • Cross-stratum orchestration and flexgrid optical networks for datacenter federations

     Velasco Esteban, Luis; Asensio, Adrià; Castro Casales, Alberto; Berral, Josep; Carrera Perez, David; Lopez, Victor; Fernández Palacios, Juan Pedro
    IEEE network
    Date of publication: 2013-11
    Journal article

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    Current inter-data-center connections are configured as static big fat pipes, which entails large bit rate over-provisioning and thus high operational costs for DC operators. On the other hand, network operators cannot share such connections between customers, because DC traffic varies greatly over time. Those connections are used to perform virtual machine migration and database synchronization among federated DCs, allowing elastic DC operations. To improve resource utilization and save costs, dynamic inter-DC connectivity is currently being targeted from a research point of view and in standardization form. In this article, we show that dynamic connectivity is not enough to guarantee elastic DC operations and might lead to poor performance provided that not enough overprovisioning of network resources is performed. To alleviate it to some extent, we propose using the flexgrid optical technology that enables finer spectrum granularity adaptation and the ability to dynamically increase and decrease the amount of optical resources assigned to connections. DCs can be interconnected through a flexgrid-based network controlled using a centralized software defined network, based on the architecture currently being proposed by the IETF; a cross-stratum orchestrator architecture coordinates DC and network elastically. Illustrative results show that dynamic elastic connectivity provides benefits by reducing the amount of overprovisioned network resources and facilitating elastic DC operations.

  • Autonomic placement of mixed batch and transactional workloads

     Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    IEEE transactions on parallel and distributed systems
    Date of publication: 2012-02-01
    Journal article

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  • A methodology for the evaluation of high response time on E-commerce users and sales

     Poggi, Nicolas; Carrera Perez, David; Gavaldà Mestre, Ricard; Ayguade Parra, Eduard; Torres Viñals, Jordi
    Information systems frontiers
    Date of publication: 2012-10-06
    Journal article

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  • Energy accounting for shared virtualized environments under DVFS using PMC-based power models

     Bertran Monfort, Ramon; Becerra Fontal, Yolanda; Carrera Perez, David; Beltran Querol, Vicenç; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Navarro Mas, Nacho; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Future generation computer systems
    Date of publication: 2012-02
    Journal article

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  • Non-intrusive estimation of QoS degradation impact on E-commerce user satisfaction

     Poggi, Nicolas; Carrera Perez, David; Gavaldà Mestre, Ricard; Ayguade Parra, Eduard
    IEEE International Symposium on Network Computing and Applications
    Presentation's date: 2011-08-26
    Presentation of work at congresses

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  • Resource-aware adaptive scheduling for MapReduce clusters

     Polo, Jordà; Castillo, Claris; Carrera Perez, David; Becerra Fontal, Yolanda; Whalley, Ian; Steinder, Malgorzata; Torres Viñals, Jordi; Ayguade Parra, Eduard
    ACM/IFIP/USENIX International Middleware Conference
    Presentation's date: 2011-12-16
    Presentation of work at congresses

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  • Black-box approach to capacity identification for multi-tier applications hosted on virtualized platforms

     Iqbal, Waheed; Dailey, Matthew; Carrera Perez, David
    International Conference on Cloud and Service Computing
    Presentation's date: 2011-12
    Presentation of work at congresses

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  • Characterization of workload and resource consumption for an online travel and booking site

     Poggi Mastrokalo, Nicolas; Carrera Perez, David; Gavaldà Mestre, Ricard; Torres Viñals, Jordi; Ayguade Parra, Eduard
    IEEE International Symposium on Workload Characterization
    Presentation's date: 2010-12-02
    Presentation of work at congresses

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  • Performance-driven task co-scheduling for MapReduce environments

     Polo, Jordà; Carrera Perez, David; Becerra Fontal, Yolanda; Torres Viñals, Jordi; Steinder, Malgorzata; Ayguade Parra, Eduard; Whalley, Ian
    IEEE Network Operations and Management Symposium (NOMS)
    Presentation's date: 2010-04-21
    Presentation of work at congresses

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    BSC contributions in energy-aware resource management for large scale distributed systems  Open access

     Torres Viñals, Jordi; Ayguade Parra, Eduard; Carrera Perez, David; Guitart Fernández, Jordi; Beltran Querol, Vicenç; Becerra Fontal, Yolanda; Badia Sala, Rosa Maria; Labarta Mancho, Jesus Jose; Valero Cortes, Mateo
    Workshop of the COST Action IC0804 on Energy Efficiency in Large Scale Distributed Systems
    Presentation's date: 2010-04-15
    Presentation of work at congresses

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    This paper introduces the work being carried out at Barcelona Supercomputing Center in the area of Green Computing. We have been working in resource management for a long time and recently we included the energy parameter in the decision process, considering that for a more sustainable science, the paradigm will shift from “time to solution” to “kWh to the solution”. We will present our proposals organized in four points that follow the cloud computing stack. For each point we will enumerate the latest achievements that will be published during 2010 that are the basics for our future research. To conclude the paper we will review our ongoing and future research work and an overview of the projects where BSC is participating.

  • Performance management of accelerated MapReduce workloads in heterogeneous clusters

     Polo, Jordà; Carrera Perez, David; Becerra Fontal, Yolanda; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    International Conference on Parallel Processing
    Presentation's date: 2010-09-16
    Presentation of work at congresses

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  • Accurate energy accounting for shared virtualized environments using PMC-based power modeling techniques

     Bertran Monfort, Ramon; Becerra Fontal, Yolanda; Carrera Perez, David; Beltran Querol, Vicenç; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Torres Viñals, Jordi; Ayguade Parra, Eduard
    ACM/IEEE International Conference on Grid Computing
    Presentation's date: 2010-10-27
    Presentation of work at congresses

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  • IBM Faculty Award

     Carrera Perez, David
    Award or recognition

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  • Adaptive resource provisioning for read intensive multi-tier applications in the cloud

     Iqbal, Waheed; Dailey, Matthew; Carrera Perez, David; Janecek, Paul
    Future generation computer systems
    Date of publication: 2010-11-04
    Journal article

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  • SLA-driven adaptive resource management for web applications on a heterogeneous compute cloud

     Iqbal, Waheed; Dailey, Matthew; Carrera Perez, David
    International Conference on Cloud Computing Technology and Science
    Presentation's date: 2009-12-01
    Presentation of work at congresses

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    Current service-level agreements (SLAs) offered by cloud providers make guarantees about quality attributes such as availability. However, although one of the most important quality attributes from the perspective of the users of a cloud-based Web application is its response time, current SLAs do not guarantee response time. Satisfying a maximum average response time guarantee for Web applications is difficult due to unpredictable traffic patterns, but in this paper we show how it can be accomplished through dynamic resource allocation in a virtual Web farm. We present the design and implementation of a working prototype built on a EUCALYPTUS-based heterogeneous compute cloud that actively monitors the response time of each virtual machine assigned to the farm and adaptively scales up the application to satisfy a SLA promising a specific average response time. We demonstrate the feasibility of the approach in an experimental evaluation with a testbed cloud and a synthetic workload. Adaptive resource management has the potential to increase the usability of Web applications while maximizing resource utilization.

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    Speeding up distributed MapReduce applications using hardware accelerators  Open access

     Becerra Fontal, Yolanda; Beltran Querol, Vicenç; Carrera Perez, David; Gonzalez Tallada, Marc; Torres Viñals, Jordi; Ayguade Parra, Eduard
    International Conference on Parallel Processing
    Presentation's date: 2009-09-22
    Presentation of work at congresses

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    In an attempt to increase the performance/cost ratio, large compute clusters are becoming heterogeneous at multiple levels: from asymmetric processors, to different system architectures, operating systems and networks. Exploiting the intrinsic multi-level parallelism present in such a complex execution environment has become a challenging task using traditional parallel and distributed programming models. As a result, an increasing need for novel approaches to exploiting parallelism has arisen in these environments. MapReduce is a data-driven programming model originally proposed by Google back in 2004 as a flexible alternative to the existing models, specially devoted to hiding the complexity of both developing and running massively distributed applications in large compute clusters. In some recent works, the MapReduce model has been also used to exploit parallelism in other non-distributed environments, such as multi-cores, heterogeneous processors and GPUs. In this paper we introduce a novel approach for exploiting the heterogeneity of a Cell BE cluster linking an existing MapReduce runtime implementation for distributed clusters and one runtime to exploit the parallelism of the Cell BE nodes. The novel contribution of this work is the design and evaluation of a MapReduce execution environment that effectively exploits the parallelism existing at both the Cell BE cluster level and the heterogeneous processors level.

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    CellMT: A cooperative multithreading library for the Cell/B.E.  Open access

     Beltran Querol, Vicenç; Carrera Perez, David; Torres Viñals, Jordi; Ayguade Parra, Eduard
    International Conference on High Performance Computing
    Presentation's date: 2009-12-16
    Presentation of work at congresses

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    The Cell BE processor has proved that heterogeneous multi-core systems can provide a huge computational power with high efficiency for a wide range of applications. The simple design of the computational units and the use of small managed local memories is the key to achieve high efficiency and performance at the same time. However, this simple and efficient hardware design comes at the price of higher code complexity. The code written to run in this kind of processors must deal with several issues such as code vectorization, loop unrolling or the explicit management of local memories. Some of these issues such as vectorization or loop unrolling can be partially solved by the compiler, but the overlapping of data transfer and computation times must be manually addressed by the programmer with techniques such as double buffering that increase the code complexity. In this paper we present a user level threading library called CellMT that effectively hide memory latencies. The concurrent execution of several threads inside each SPU naturally overlaps computation and data transfer times without increasing the code complexity. To prove the suitability and feasibility of our multi-threaded library, we perform an exhaustive performance evaluation with a synthetic benchmark and a real application. The experimental results show that the multithreaded approach can outperform a hand-coded double buffering scheme, with speedups from 0.96x to 3.2x, while maintaining the complexity of a naive buffering scheme.

  • MPEXPAR: MODELS DE PROGRAMACIO I ENTORNS D'EXECUCIO PARAL·LELS

     Gonzalez Tallada, Marc; Alonso López, Javier; Sirvent Pardell, Raül; Guitart Fernández, Jordi; Carrera Perez, David; Martorell Bofill, Xavier; Torres Viñals, Jordi; Badia Sala, Rosa Maria; Cortes Rossello, Antonio; Corbalan Gonzalez, Julita; Costa Prats, Juan Jose; Farreras Esclusa, Montserrat; Gil Gómez, Maria Luisa; Navarro Mas, Nacho; Herrero Zaragoza, José Ramón; Tejedor Saavedra, Enric; Becerra Fontal, Yolanda; Nou Castell, Ramon; Labarta Mancho, Jesus Jose; Ayguade Parra, Eduard
    Participation in a competitive project

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  • Adaptive task scheduling for multi-job MapReduce environments

     Polo, Jordà; Nadal, David de; Becerra Fontal, Yolanda; Beltran Querol, Vicenç; Ayguade Parra, Eduard; Carrera Perez, David; Torres Viñals, Jordi
    Jornadas de Paralelismo
    Presentation's date: 2009-09
    Presentation of work at congresses

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    Batch job profiling and adaptive profile enforcement for virtualized environments  Open access

     Becerra Fontal, Yolanda; Carrera Perez, David; Ayguade Parra, Eduard
    Euromicro International Conference on Parallel, Distributed, and Network-Based Processing
    Presentation's date: 2009-02
    Presentation of work at congresses

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    Data center management is driven by high-level performance goals, and it is the responsibility of a management middleware to ensure that those goals are met using dynamic resource allocation. The performance delivered by the heterogeneous set of applications running in a virtualized enterprise data center must be predicted to make resource allocation decisions. For some of these applications, it is required to produce accurate profiles based on previous executions: that is the case of batch jobs. In this paper we propose a methodology to produce resource consumption profiles for batch applications running inside of virtual machines and a technique to enforce and adapt the profiles to actual execution conditions and application performance. For this purpose we have developed a testing prototype. The enforcement technique observes the fact that management middleware usually run in control cycles in which the system can be reconfigured, what imposes a tradeoff between the accuracy of the profiles and their applicability in real deployments. The novel contribution of this work is the study of the tradeoff between accuracy and applicability of workload profiles, what is a necessary step to enable existing management middleware with the performance prediction mechanisms required to perform effective dynamic resource allocation.

  • A hybrid connector for efficient web servers

     Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    International journal of high performance computing and networking
    Date of publication: 2008-10
    Journal article

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    In this paper we introduce a novel Web server architecture that combines the best aspects of both the multithreaded and the event-driven architectures, the two major existing alternatives, to create a server model that offers an improved performance in terms of user session completions without losing the natural ease of programming characteristic of the multithreading paradigm. We describe the implementation of this architecture on the Tomcat 5.5 server and evaluate its performance. The obtained results demonstrate the feasibility of the hybrid architecture and the performance benefits that this model introduces for e-commerce applications.

  • Enabling Resource Sharing between Transactional and Batch Workloads Using Dynamic Application Placement

     Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Lecture notes in computer science
    Date of publication: 2008-12
    Journal article

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  • Adaptive execution environments for application servers  Open access

     Carrera Perez, David
    Defense's date: 2008-07-08
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    El creixement experimentat tant per la web com per Internet en els últims anys ha potenciat l'introducció de servidors d'aplicacions dins de la majoria d'entorns d'execució distribuits. El servidors d'aplicacions web porten les aplicacions distribuides un pas endavant pel que fa a accessibilitat, facilitat d'ús i estandardització, mitjançant l'ús dels protocols de comunicació més extesos i proveïnt rics entorns de desenvolupament.Seguint l'evolució dels entorns d'execució dels servidors d'aplicacions, els factors que determinin el seu rendiment també ha evolucionat, amb l'aparició de nous factors relacionats amb la creixent complexitat de l'entorn, mentres que els ja existents que determinaven el rendiment dels servidors d'aplicacions en les etapes inicials d'aquesta tecnologia encara són importants en l'actualitat. Inicialment, el rendiment d'un servidor d'aplicacions era principalment determinat pel comportament de la seva pila d'execució local, que normalment era l'origen de tots els problemes de rendiment. Més tard, quan el middleware va esdevenir més eficient, més càrrega es podia executar en cada instància del servidor d'aplicacions i per tant la gestió d'un nombre gran de clients va resultar ser un nou punt calent en termes de rendiment. Finalment, quan la capacitat d'un node va ser sobrepassada, els entorns d'execució van esdevenir massivament clusteritzats per tal de dividir la càrrega entre un nombre gran d'instàncies de servidors d'aplicacions, fet aquest que va significar que cadascuna de les instàncies havia de rebre una certa quantitat de recursos del sistema. El resultat d'aquest procés és que fins i tot en l'arquitectura de gestió del servei més avançada que pugui ser trobada avui dia, 1) comprendre l'impacte de rendiment causat per la pila d'execució del servidor d'aplicacions, 2) gestionar eficientment les connexions dels clients, i 3) assignar recursos adequadament a cada instància del servidor d'aplicacions, són tres passos incrementals de vital importància per tal d'optimitzar el rendiment d'un entorn tan complex. I donada la mida i complexitat dels centres de processat de dades actuals, tots aquests passos haurien de funcionar de manera automàtica sense necessitat d'intervenció humana.Seguint els tres elements presentats abans, aquesta tesis aporta a la gestió del rendiment dels complexos entorns d'execució per a servidors d'aplicacions tres contribucions: 1) la proposta d'un entorn de monitorització automàtic que proporciona important informació de rendiment dins del contexte d'un sol node; 2) la proposta i evaluació d'un nou disseny arquitectònic per a servidors d'aplicacions que millora l'adaptabilitat en condicions de càrrega variable; i 3) la proposta i evaluació d'una tècnica d'assignació automàtica de recursos per entorns d'execució virtualitzats i clusteritzats. La suma de les tres contribucions proposades en aquesta tesis proporcionen un nou rang d'opcions per a millorar el rendiment del sistema tant off-line (1) com on-line (2 i 3).

    The growth experienced by the web and by the Internet over the last years has fuelled web application servers to break into most of the existing distributed execution environments. Web application servers take distributed applications one step forward in their accessibility, easiness of development and standardization, by using the most extended communication protocols and by providing rich development frameworks.Following the evolution of the application server execution environment, the factors that determine their performance have evolved too, with new ones that have come out with the raising complexity of the environment, while the already known ones that determined the performance in the early stages of the application server technology remain relevant in modern scenarios. In the old times, the performance of an application server was mainly determined by the behavior of its local execution stack, what usually resulted to be the source of most performance bottlenecks. Later, when the middleware became more efficient, more load could be put on each application server instance and thus the management of such a large number of concurrent client connections resulted to be a new hot spot in terms of performance. Finally, when the capacity of any single node was exceeded, the execution environments were massively clusterized to spread the load across a very large number of application server instances, what meant that each instance was allocated a certain amount of resources. The result of this process is that even in the most advanced service management architecture that can be currently found, 1) understanding the performance impact caused by the application server execution stack, 2) efficiently managing client connections, and 3) adequately allocating resources to each application server instance, are three incremental steps of crucial importance in order to optimize the performance of such a complex facility. And given the size and complexity of modern data centers, all of them should operate automatically without need of human interaction.Following the three items described above, this thesis contributes to the performance management of a complex application server execution environment by 1) proposing an automatic monitoring framework that provides a performance insight in the context of a single machine; 2) proposing and evaluating a new architectural application server design that improves the adaptability to changing workload conditions; and 3) proposing and evaluating an automatic resource allocation technique for clustered and virtualized execution environments. The sum of the three techniques proposed in this thesis opens up a new range of options to improve the performance of the system both off-line (1) and on-line (2 and 3).

  • Tailoring Resources: The Energy Efficient Consolidation Strategy Goes Beyond Virtualization

     Torres Viñals, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Poggi, Nicolas; Hogan, Kevin; Berral Garcia, Josep Lluis; Moreno, Antoni; Ayguade Parra, Eduard; Gavaldà Mestre, Ricard; Guitart Fernández, Jordi
    IEEE International Conference on Autonomic Computing
    Presentation's date: 2008-06-02
    Presentation of work at congresses

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  • Reducing Wasted Resources to Help Achieve Green Data Centers

     Torres Viñals, Jordi; Carrera Perez, David; Kevin, Hogan; Gavaldà Mestre, Ricard; Beltran Querol, Vicenç; Nicolás, Poggi
    IEEE International Parallel and Distributed Processing Symposium
    Presentation's date: 2008-04-14
    Presentation of work at congresses

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  • Dynamic CPU provisioning for self-managed secure web applications in SMP hosting platforms

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Computer networks
    Date of publication: 2008-05
    Journal article

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    Overload control mechanisms such as admission control and connection differentiation have proven effective for preventing overload of application servers running secure web applications. However, achieving optimal results in overload prevention is only possible when some kind of resource management is considered in addition to these mechanisms. In this paper we propose an overload control strategy for secure web applications that brings together dynamic provisioning of platform resources and admission control based on secure socket layer (SSL) connection differentiation. Dynamic provisioning enables additional resources to be allocated to an application on demand to handle workload increases, while the admission control mechanism avoids the server¿s performance degradation by dynamically limiting the number of new SSL connections accepted and preferentially serving resumed SSL connections (to maximize performance on session-based environments) while additional resources are being provisioned. Our evaluation demonstrates the benefit of our proposal for efficiently managing the resources and preventing server overload on a 4-way multiprocessor Linux hosting platform, especially when the hosting platform is fully overloaded.

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    Managing SLAs of heterogeneous workloads using dynamic application placement  Open access

     Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    International Symposium on High Performance Distributed Computing
    Presentation's date: 2008-06-23
    Presentation of work at congresses

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    In this paper we address the problem of managing heterogeneous workloads in a virtualized data center. We consider two different workloads: transactional applications and long-running jobs. We present a technique that permits collocation of these workload types on the same physical hardware. Our technique dynamically modifies workload placement by leveraging control mechanisms such as suspension and migration, and strives to optimally trade off resource allocation among these workloads in spite of their differing characteristics and performance objectives. Our approach builds upon our previous work on dynamically placing transactional workloads. This paper extends our framework with the capability to manage long-running workloads. We achieve this goal by using utility functions, which permit us to compare the performance of various workloads, and which are used to drive allocation decisions. We demonstrate that our technique maximizes heterogeneous workload performance while providing service differentiation based on high-level performance goals.

  • Enabling resource sharing between transactional and batch workloads using dynamic application placement

     Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    ACM/IFIP/USENIX International Middleware Conference
    Presentation's date: 2008-12-01
    Presentation of work at congresses

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    Utility-based placement of dynamic web applications with fairness goals  Open access

     Carrera Perez, David; Steinder, Malgorzata; Whalley, Ian; Torres Viñals, Jordi; Ayguade Parra, Eduard
    IEEE/ IFIP Network Operations and management Symposium
    Presentation's date: 2008-04-07
    Presentation of work at congresses

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    We study the problem of dynamic resource allocation to clustered Web applications. We extend application server middleware with the ability to automatically decide the size of application clusters and their placement on physical machines. Unlike existing solutions, which focus on maximizing resource utilization and may unfairly treat some applications, the approach introduced in this paper considers the satisfaction of each application with a particular resource allocation and attempts to at least equally satisfy all applications. We model satisfaction using utility functions, mapping CPU resource allocation to the performance of an application relative to its objective. The demonstrated online placement technique aims at equalizing the utility value across all applications while also satisfying operational constraints, preventing the over-allocation of memory, and minimizing the number of placement changes. We have implemented our technique in a leading commercial middleware product. Using this real-life testbed and a simulation we demonstrate the benefit of the utility-driven technique as compared to other state-of-the-art techniques.

    We study the problem of dynamic resource allocation to clustered Web applications. We extend application server middleware with the ability to automatically decide the size of application clusters and their placement on physical machines. Unlike existing solutions, which focus on maximizing resource utilization and may unfairly treat some applications, the approach introduced in this paper considers the satisfaction of each application with a particular resource allocation and attempts to at least equally satisfy all applications. We model satisfaction using utility functions, mapping CPU resource allocation to the performance of an application relative to its objective. The demonstrated online placement technique aims at equalizing the utility value across all applications while also satisfying operational constraints, preventing the over-allocation of memory, and minimizing the number of placement changes. We have implemented our technique in a leading commercial middleware product. Using this real-life testbed and a simulation we demonstrate the benefit of the utility-driven technique as compared to other state-of-the-art techniques.

  • Designing an overload control strategy for secure e-commerce applications

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Computer networks
    Date of publication: 2007-10
    Journal article

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    Uncontrolled overload can lead e-commerce applications to considerable revenue losses. For this reason, overload prevention in these applications is a critical issue. In this paper we present a complete characterization of secure e-commerce applications scalability to determine which are the bottlenecks in their performance that must be considered for an overload control strategy. With this information, we design an adaptive session-based overload control strategy based on SSL (Secure Socket Layer) connection differentiation and admission control. The SSL connection differentiation is a key factor because the cost of establishing a new SSL connection is much greater than establishing a resumed SSL connection (it reuses an existing SSL session on the server). Considering this big difference, we have implemented an admission control algorithm that prioritizes resumed SSL connections to maximize the performance in session-based environments and dynamically limits the number of new SSL connections accepted, according to the available resources and the current number of connections in the system, in order to avoid server overload. Our evaluation on a Tomcat server demonstrates the benefit of our proposal for preventing server overload.

  • Server virtualization in autonomic management of heterogeneous workloads

     Steinder, Malgorzata; Whalley, Ian; Carrera Perez, David; Gaweda, Ilona
    10th IFIP/IEEE Symposium on Integrated Network Management
    Presentation of work at congresses

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  • Monitoring and analysis framework for grid middleware

     Nou Castell, Ramon; Ferran, Julia; Carrera Perez, David; Kevin, Hogan; Caubet Serrabou, Jordi; Labarta Mancho, Jesus Jose; Torres Viñals, Jordi
    Euromicro International Conference on Parallel, Distributed, and Network-Based Processing
    Presentation of work at congresses

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    Performance impact of the grid middleware  Open access

     Carrera Perez, David; Guitart Fernández, Jordi; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Date of publication: 2006-01
    Book chapter

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    The Open Grid Services Architecture (OGSA) defines a new vision of the Grid based on the use of Web Services (Grid Services). The standard interfaces, behaviors and schemes that are consistent with the OGSA specification are defined by the Open Grid Service Infrastructure (OGSI). Grid Services, as an extension of the Web Services, run on top of rich execution frameworks that make them accessible and interoperable with other applications. Two examples of these frameworks are Sun’s J2EE platform and Microsoft’s .NET. The Globus Project implements the OGSI Specification for the J2EE framework in the Globus Toolkit. As any J2EE application, the performance of the Globus Toolkit is constrained by the performance obtained by the J2EE execution stack This performance can be influenced by many points of the execution stack: operating system, JVM, middleware or the same grid service, without forgetting the processing overheads related to the parsing of the communication protocols. In the scope of this chapter, all this levels together will be referred to as the grid middleware. In order to avoid the grid middleware to become a performance bottleneck for a distributed grid-enabled application, grid nodes have to be tuned for an efficient execution of I/O intensive applications because they can receive a high volume of requests every second and have to deal with a big amount of invocations, message parsing operations and a continuous task of marshaling and unmarshalling service parameters. All the parameters of the system affecting these operations have to be tuned according with the expected system load intensity. A Grid node is connected to to other nodes through a network connection which is also a decisive factor to obtain a high performance for a grid application. If the inter-node data transmission time overlaps completely the processing time for a computational task, the benefits of the grid architecture will be lost. Additionally, in many situations the content exchanged between grid nodes can be considered confidential and should be protected from curious sights. But the cost of data encryption/decryption can be an important performance weak that must be taken into account. In this chapter we will study the process of receiving and executing a Grid job from the perspective of the underlying levels existing below the Grid application. We will analyze the different performance parameters that can influence in the performance of the Grid middleware and will show the general schema of tasks involved in the service of an execution request.

    Postprint (author’s final draft)

  • Monitoring and analysing a grid middleware node

     Nou Castell, Ramon; Ferran, Julià; Carrera Perez, David; Kevin, Hogan; Caubet Serrabou, Jordi; Labarta Mancho, Jesus Jose; Torres Viñals, Jordi
    ACM/IEEE International Conference on Grid Computing
    Presentation's date: 2006-09-28
    Presentation of work at congresses

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  • Performance Impact of the Grid Middleware

     Carrera Perez, David
    ENGINEERING THE GRID Status and Perspective
    Presentation's date: 2006-06-01
    Presentation of work at congresses

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  • Preventing Secure Web Applications Overload through Dynamic Resource Provisioning and Admission Control

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Date: 2006-11
    Report

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  • Monitoring and analysis framework for Java middlewares

     Nou Castell, Ramon; Ferran, Julià; Carrera Perez, David; Kevin, Hogan; Caubet Serrabou, Jordi; Labarta Mancho, Jesus Jose; Torres Viñals, Jordi
    Date: 2006-10
    Report

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  • Experiences with simulations a light and fast model for secure web applications

     Nou Castell, Ramon; Guitart Fernández, Jordi; Carrera Perez, David; Torres Viñals, Jordi
    IEEE International Conference on Parallel and Distributed Systems
    Presentation's date: 2006-07-12
    Presentation of work at congresses

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  • A Hybrid Web Server Architecture for Secure e-Business Web Applications

     Beltran Querol, Vicenç; Carrera Perez, David; Guitart Fernández, Jordi; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Lecture notes in computer science
    Date of publication: 2005-09
    Journal article

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  • A hybrid web server architecture for e-commerce applications

     Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    IEEE International Conference on Parallel and Distributed Systems
    Presentation of work at congresses

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    The performance of an e-commerce application can be measured according to technical metrics but also following business indicators. The revenue obtained by a commercial Web application is directly related to the amount of clients that complete business transactions. In technical terms, a business transaction is completed when a Web client successfully finishes a browsing session. In this paper we introduce a novel Web server architecture that combines the best aspects of both the multithreaded and the event-driven architectures, the two major existing alternatives, to create a server model that offers an improved performance in terms of user session completions without loosing the natural ease of programming characteristic of the multithreading paradigm. We describe the implementation of this architecture on the Tomcat 5.5 server and evaluate its performance. The obtained results demonstrate the feasibility of the hybrid architecture and the performance benefits that this model introduces for e-commerce applications.

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    Simulating complex systems with a low-detail model  Open access

     Nou Castell, Ramon; Guitart Fernández, Jordi; Beltran Querol, Vicenç; Carrera Perez, David; Montero Mercade, Lidia; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Jornadas de Paralelismo
    Presentation's date: 2005-09-15
    Presentation of work at congresses

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    In this paper we show how modeling and simulating a complex system such as a web-server can help to evaluate di erent metrics and proposals to improve the performance without necessity of using a real system. Many times the system is unavailable or requires spending time and resources to generate results. With simulation and concretely with a coarse-grain simulation as we propose can solve with great success this problem. In this article we have been able to simulate the metric and behaviour of a web server with SSL security, the ellapsed time required by the simulation on a desktop machine is only 1/10 of real time. We have also been able to measure, for example,the performance enhancements with 8 CPUs without having an available machine of similar features.

  • Tuning Dynamic Web Applications using Fine-Grain Analysis

     Guitart Fernández, Jordi; Carrera Perez, David; Torres Viñals, Jordi; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    Euromicro International Conference on Parallel, Distributed, and Network-Based Processing
    Presentation's date: 2005-02-09
    Presentation of work at congresses

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  • Simulating and Modeling Secure e-Business Aplications

     Nou Castell, Ramon; Guitart Fernández, Jordi; Beltran Querol, Vicenç; Carrera Perez, David; Montero, L; Torres Viñals, Jordi
    Date: 2005-12
    Report

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  • Monitoring and analysis framework for Java middlewares

     Nou Castell, Ramon; Julia, F; Carrera Perez, David; Hogan, K; Caubet Serrabou, Jordi; Labarta Mancho, Jesus Jose; Torres Viñals, Jordi
    Date: 2005-10
    Report

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  • Characterizing Secure Dynamic Web Applications Scalability

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Date: 2005-03
    Report

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  • Session-Based Adaptive Overload Control for Dynamic Web Applications in Secure Environments

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Torres Viñals, Jordi; Ayguade Parra, Eduard
    Date: 2005-03
    Report

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  • Session-Based Adaptive Overload Control for Secure Dynamic Web Applications

     Guitart Fernández, Jordi; Carrera Perez, David; Beltran Querol, Vicenç; Ayguade Parra, Eduard; Torres Viñals, Jordi
    International Conference on Parallel Processing
    Presentation's date: 2005-06-14
    Presentation of work at congresses

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  • WAS Control Center: An Autonomic Performance-Triggered Tracing Environment for WebSphere

     Carrera Perez, David; Garcia, David; Torres Viñals, Jordi; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    Euromicro International Conference on Parallel, Distributed, and Network-Based Processing
    Presentation of work at congresses

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