The processing elements of many modern tightly coupled multicomputers are connected via mesh or toroidal networks. Such interconnects are simple and highly scalable, but suffer from high fragmentation, low utilization, and insufficient fault tolerance when the resources allocated to each job are dedicated. High-dimensional interconnects may be more efficient in certain cases, but are based on complex and expensive components and scale poorly. We present a novel hardware/software architectural approach that detaches the processing elements of the system from the interconnect and augments the traditional toroidal topology to provide additional connectivity options and additional link redundancy. We explore the properties of the new "multitoroidal" topology and the improvements it offers in resource utilization and failure tolerance. We present the results of extensive simulation studies to show that for practically important types of workloads, the resource utilization may be increased by 50 percent and, in certain cases, as much as 100 percent compared to toroidal machines and is, in fact, close to the theoretically optimal case of a full crossbar interconnect. The combined hardware/software architectural innovation is a major significant improvement in resource utilization on top of the state of the art in scheduling algorithm research. Also, multitoroidal multicomputers are able to work under link failure rates of 0.002 failures per week that would shut down toroidal machines. A variant of the multitoroidal architecture is implemented in the Blue Gene/L supercomputer.

Heterogeneous clusters and grid infrastructures are becoming increasingly popular. In these computing infrastructures, machines have different resources (e.g., memory sizes, disk space, and installed software packages). These differences give rise to a problem of over-provisioning, that is, sub-optimal utilization of a cluster due to users requesting resource capacities greater than what their jobs actually need. Our analysis of a real workload file (LANL CM 5) revealed differences of up to two orders of magnitude between requested memory capacity and actual memory usage. The problem of over-provisioning has received very little attention so far. We discuss different approaches for applying machine learning methods to estimate the actual resource capacities used by jobs. These approaches are independent of the scheduling policies and the dynamic resource-matching schemes used. Our simulations show that these methods can yield an improvement of over 50% in utilization (throughput) of heterogeneous clusters

Machine virtualization has emerged as a key technology for server consolidation and on-demand server provisioning. To support this trend, it is essential to improve the performance of virtualization software and hence enable the efficient running of many virtual machines. We present a virtualization system that can dynamically extend the real memory of its guest virtual machines. We describe an implementation of dynamic memory extension for Linux guests running on the IBM zVM virtualization environment. Our implementation for the Linux extension is based on device drivers for accessing these dynamic memory extensions. Moreover, we show that this new capability can improve utilization and performance of the Linux guests in our virtualization environment. Specifically, memory management is improved and more virtual machines can run at a given moment. We study the utilization of dynamic memory extension of a Linux guest for a JVM heap. Running Specjbb2000 benchmark on a small virtual machine extended with dynamic memory to host the heap, we measured an improvement in transaction throughput and a 23.23% reduction in paging activity compared to an initially large machine. We further studied the implication of our experiments on the number of virtual machines that can run efficiently.

This paper gives an overview of the BlueGene/L Supercomputer. This is a jointly funded research partnership between IBM and the Lawrence Livermore National Laboratory as part of the United States Department of Energy ASCI Advanced Architecture Research Program. Application performance and scaling studies have recently been initiated with partners at a number of academic and government institutions,including the San Diego Supercomputer Center and the California Institute of Technology. This massively parallel system of 65,536 nodes is based on a new architecture that exploits system-on-a-chip technology to deliver target peak processing power of 360 teraFLOPS (trillion floating-point operations per second). The machine is scheduled to be operational in the 2004-2005 time frame, at price/performance and power consumption/performance targets unobtainable with conventional architectures.

Mobile knowledge seekers often need access to information on the Web during a meeting or on the road, while away from their desktop. A common practice today is to use pervasive devices such as Personal Digital Assistants or mobile phones. However, these devices have inherent constraints (e.g., slow communication, form factor) which often make information discovery tasks impractical.In this paper, we present a new focused-search approach specifically oriented for the mode of work and the constraints dictated by pervasive devices. It combines focused search within specific topics with encapsulation of topic-specific information in a persistent repository. One key characteristic of these persistent repositories is that their footprint is small enough to fit on local devices, and yet they are rich enough to support many information discovery tasks in disconnected mode. More specifically, we suggest a representation for topic-specific information based on "knowledge-agent bases" that comprise all the information necessary to access information about a topic (under the form of key concepts and key Web pages) and assist in the full search process from query formulation assistance to result scanning on the device itself. The key contribution of our work is the coupling of focused search with encapsulated knowledge representation making information discovery from pervasive devices practical as well as efficient. We describe our model in detail and demonstrate its aspects through sample scenarios.

Mobile agents is an important enabling technology for certain types of real world applications such as e-commerce and workflows. While the potential benefits are appealing, this technology is not being used by many applications. This is largely attributed to the lack of components such as transactions and their integration with de-facto technologies. This work focuses on bridging this gap and devising an extended transactional model for mobile agents. The nature of mobile agents for autonomous processing and mobility introduces numerous challenges with respect to transactions which are originally, addressed in our work. First, given that, unstructured, execution scripts for agents, it is necessary to isolate side-effects that occur between two successive migrations to later be able to commit or abort them locally according to transaction semantics maintained across multiple hosts. Second, intra-transaction parallelism requires synchronization among multiple autonomous agents to join their processing and to rollback a transaction. Third, recovery from failures at a specific host, may necessitate maintaining a global state of a transaction across all the agent's destinations to determine how to proceed (e.g., repeat activities upon recovery). This paper presents a comprehensive transaction model for mobile agents and its deployment in the context of Java-based mobile agents. The overall complexity of transaction management is handled using a division of labor between an object-oriented programming model, protocols and a concurrency control mechanism. Specifically, the programming model maintains separation of concerns between mobility, transactions and application logic in order to cope with the aforementioned challenges.

Article Knowledge encapsulation for focused search from pervasive devices Share on Authors: Yariv Aridor IBM Research Lab in Haifa, Matam, Haifa 31905, Israel IBM Research Lab in Haifa, Matam, Haifa 31905, IsraelView Profile , David Carmel IBM Research Lab in Haifa, Matam, Haifa 31905, Israel IBM Research Lab in Haifa, Matam, Haifa 31905, IsraelView Profile , Yoëlle S. Maarek IBM Research Lab in Haifa, Matam, Haifa 31905, Israel IBM Research Lab in Haifa, Matam, Haifa 31905, IsraelView Profile , Aya Soffer IBM Research Lab in Haifa, Matam, Haifa 31905, Israel IBM Research Lab in Haifa, Matam, Haifa 31905, IsraelView Profile , Ronny Lempel Department of Computer Science, Technion, Haifa 32000, Israel Department of Computer Science, Technion, Haifa 32000, IsraelView Profile Authors Info & Claims WWW '01: Proceedings of the 10th international conference on World Wide WebMay 2001 Pages 754–764https://doi.org/10.1145/371920.372195Online:01 April 2001Publication History 8citation368DownloadsMetricsTotal Citations8Total Downloads368Last 12 Months2Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Abstract The cluster virtual machine (VM) for Java provides a single system image of a traditional Java Virtual Machine (JVM) while executing in a distributed fashion on the nodes of a cluster. The cluster VM for Java virtualizes the cluster, supporting any pure Java application without requiring that application be tailored specifically for it. The aim of our cluster VM is to obtain improved scalability for a class of Java Server Applications by distributing the application's work among the cluster's computing resources. The implementation of the cluster VM for Java is based on a novel object model which distinguishes between an application's view of an object (e.g. every object is a unique data structure) and its implementation (e.g. objects may have consistent replications on different nodes). This enables us to exploit knowledge on the use of individual objects to improve performance (e.g. using object replications to increase locality of access to objects). We have already completed a prototype that runs pure Java applications on a cluster of NT workstations connected by a Myrinet fast switch. The prototype provides a single system image to applications, distributing the application's threads and objects over the cluster. We used the cluster VM to run, without change, arealJava Server Application containing over 10 Kloc Kloc means Kilo lines of code—used to describe the size of applications in terms of source lines count. for the source code and achieved high scalability for it on a cluster. We also achieved linear speedup for another application with a large number of independent threads. This paper discusses the architecture and implementation of the cluster VM. It focuses on achieving a single system image for a traditional JVM on a cluster while describing, in short, how we aim to obtain scalability. Copyright © 2001 John Wiley & Sons, Ltd.

Abstract Component mobility is an important enabling technology for the design of wide area pervasive applications, but it introduces new challenges in the critical aspect of access control. In particular, when mobility is used for dynamic relocation of distributed components, access from both remote and local mobile components needs to be uniformly controlled. The dynamic determination of execution location, possibly crossing multiple administrative authorities, requires dynamic establishment and enforcement of access control. The deployment over widely heterogeneous hosts and devices requires integration of access control with dynamic probing of resource availability so as to influence the relocation process. This paper presents a model for dynamic specification and enforcement of access control in the context of dynamically relocatable components, and an implementation in the Java‐basedFarGoframework. The specification follows a negotiation‐based protocol that enables dynamic matching of available and required resources by providers and consumers, respectively. Enforcement is provided through a capability‐based secure component reference architecture, which uniformly applies to both local and remote references, and through instance‐level, as opposed to type‐level (supported in Java), access control. Finally, access control is integrated into the programming model in a non‐intrusive fashion, by separating the encoding of access control from the encoding of the logic of the application. Copyright © 2001 John Wiley & Sons, Ltd.

cJVM is a Java Virtual Machine (JVM) that provides a single system image of a traditional JVM while executing on a cluster. cJVM virtualizes the cluster, supporting any pure Java application without requiring any code modifications. By distributing the application's work among the cluster's nodes, cJVM aims to obtain improved scalability for Java Server Applications. cJVM uses a novel object model which distinguishes between an application's view of an object and its implementation (e.g., different objects of the same class may have different implementations). This allows us to exploit knowledge on the usage of individual objects to improve performance. cJVM is work-in-progress. Our prototype runs on a cluster of IBM IntelliStations running Win/NT and are connected via a Myrinet switch. It provides a single system image to applications, distributing the application's threads and objects over the cluster. We have used cJVM to run without change a real Java application containing over 10Kloc and have achieved linear speedup for another application with a large number of independent threads. This paper discusses cJVM's architecture and implementation, showing how to provide a single system image of a traditional JVM on a cluster.