Abstract: A virtualized system includes a new layer of software, the virtual machine monitor. The VMM's principal role is to arbitrate accesses to the underlying physical host platform's resources so that multiple operating systems (which are guests of the VMM) can share them. The VMM presents to each guest OS a set of virtual platform interfaces that constitute a virtual machine (VM). Once confined to specialized, proprietary, high-end server and mainframe systems, virtualization is now becoming more broadly available and is supported in off-the-shelf systems based on Intel architecture (IA) hardware. This development is due in part to the steady performance improvements of IA-based systems, which mitigates traditional virtualization performance overheads. Intel virtualization technology provides hardware support for processor virtualization, enabling simplifications of virtual machine monitor software. Resulting VMMs can support a wider range of legacy and future operating systems while maintaining high performance.

Abstract: Developed more than 30 years ago to address mainframe computing problems, virtual machine monitors have resurfaced on commodity platforms, offering novel solutions to challenges in security, reliability, and administration Stanford University researchers began to look at the potential of virtual machines to overcome difficulties that hardware and operating system limitations imposed: This time the problems stemmed from massively parallel processing (MPP) machines that were difficult to program and could not run existing operating systems With virtual machines, researchers found they could make these unwieldy architectures look sufficiently similar to existing platforms to leverage the current operating systems From this project came the people and ideas that underpinned VMware Inc, the original supplier of VMMs for commodity computing hardware The implications of having a VMM for commodity platforms intrigued both researchers and entrepreneurs

Abstract: This paper describes the new Java memory model, which has been revised as part of Java 5.0. The model specifies the legal behaviors for a multithreaded program; it defines the semantics of multithreaded Java programs and partially determines legal implementations of Java virtual machines and compilers.The new Java model provides a simple interface for correctly synchronized programs -- it guarantees sequential consistency to data-race-free programs. Its novel contribution is requiring that the behavior of incorrectly synchronized programs be bounded by a well defined notion of causality. The causality requirement is strong enough to respect the safety and security properties of Java and weak enough to allow standard compiler and hardware optimizations. To our knowledge, other models are either too weak because they do not provide for sufficient safety/security, or are too strong because they rely on a strong notion of data and control dependences that precludes some standard compiler transformations.Although the majority of what is currently done in compilers is legal, the new model introduces significant differences, and clearly defines the boundaries of legal transformations. For example, the commonly accepted definition for control dependence is incorrect for Java, and transformations based on it may be invalid.In addition to providing the official memory model for Java, we believe the model described here could prove to be a useful basis for other programming languages that currently lack well-defined models, such as C++ and C#.

Abstract: A virtual machine can support individual processes or a complete system depending on the abstraction level where virtualization occurs. Some VMs support flexible hardware usage and software isolation, while others translate from one instruction set to another. Virtualizing a system or component -such as a processor, memory, or an I/O device - at a given abstraction level maps its interface and visible resources onto the interface and resources of an underlying, possibly different, real system. Consequently, the real system appears as a different virtual system or even as multiple virtual systems. Interjecting virtualizing software between abstraction layers near the HW/SW interface forms a virtual machine that allows otherwise incompatible subsystems to work together. Further, replication by virtualization enables more flexible and efficient and efficient use of hardware resources.

Abstract: A management capability is provided for a virtual computing platform. In one example, this platform allows interconnected physical resources such as processors, memory, network interfaces and storage interfaces to be abstracted and mapped to virtual resources (e.g., virtual mainframes, virtual partitions). Virtual resources contained in a virtual partition can be assembled into virtual servers that execute a guest operating system (e.g., Linux). In one example, the abstraction is unique in that any resource is available to any virtual server regardless of the physical boundaries that separate the resources. For example, any number of physical processors or any amount of physical memory can be used by a virtual server even if these resources span different nodes. A virtual computing platform is provided that allows for the creation, deletion, modification, control (e.g., start, stop, suspend, resume) and status (i.e., events) off the virtual servers which execute on the virtual computing platform and the management capability provides controls for these functions. In a particular example, such a platform allows the number and type of virtual resources consumed by a virtual server to be scaled up or down when the virtual server is running. For instance, an administrator may scale a virtual server manually or may define one or more policies that automatically scale a virtual server. Further, using the management API, a virtual server can monitor itself and can scale itself up or down depending on its need for processing, memory and I/O resources. For example, a virtual server may monitor its CPU utilization and invoke controls through the management API to allocate a new processor for itself when its utilization exceeds a specific threshold. Conversely, a virtual server may scale down its processor count when its utilization falls. Policies can be used to execute one or more management controls. More specifically, a management capability is provided that allows policies to be defined using management object's properties, events and/or method results. A management policy may also incorporate external data (e.g., an external event) in its definition. A policy may be triggered, causing the management server or other computing entity to execute an action. An action may utilize one or more management controls. In addition, an action may access external capabilities such as sending notification e-mail or sending a text message to a telephone paging system. Further, management capability controls may be executed using a discrete transaction referred to as a 'job.' A series of management controls may be assembled into a job using one or management interfaces. Errors that occur when a job is executed may cause the job to be rolled back, allowing affected virtual servers to return to their original state.

Abstract: Virtual Machine technology applies the concept of virtualization to an entire machine, circumventing real machine compatibility constraints and hardware resource constraints to enable a higher degree of software portability and flexibility. Virtual machines are rapidly becoming an essential element in computer system design. They provide system security, flexibility, cross-platform compatibility, reliability, and resource efficiency. Designed to solve problems in combining and using major computer system components, virtual machine technologies play a key role in many disciplines, including operating systems, programming languages, and computer architecture. For example, at the process level, virtualizing technologies support dynamic program translation and platform-independent network computing. At the system level, they support multiple operating system environments on the same hardware platform and in servers. Historically, individual virtual machine techniques have been developed within the specific disciplines that employ them (in some cases they aren’t even referred to as “virtual machines?), making it difficult to see their common underlying relationships in a cohesive way. In this text, Smith and Nair take a new approach by examining virtual machines as a unified discipline. Pulling together cross-cutting technologies allows virtual machine implementations to be studied and engineered in a well-structured manner. Topics include instruction set emulation, dynamic program translation and optimization, high level virtual machines (including Java and CLI), and system virtual machines for both single-user systems and servers. * Examines virtual machine technologies across the disciplines that use them—operating systems, programming languages and computer architecture—defining a new and unified discipline. * Reviewed by principle researchers at Microsoft, HP, and by other industry research groups. * Written by two authors who combine several decades of expertise in computer system research and development, both in academia and industry.

Abstract: Virtual Machine (VM) environments (e.g., VMware and Xen) are experiencing a resurgence of interest for diverse uses including server consolidation and shared hosting. An application's performance in a virtual machine environment can differ markedly from its performance in a non-virtualized environment because of interactions with the underlying virtual machine monitor and other virtual machines. However, few tools are currently available to help debug performance problems in virtual machine environments.In this paper, we present Xenoprof, a system-wide statistical profiling toolkit implemented for the Xen virtual machine environment. The toolkit enables coordinated profiling of multiple VMs in a system to obtain the distribution of hardware events such as clock cycles and cache and TLB misses. The toolkit will facilitate a better understanding of performance characteristics of Xen's mechanisms allowing the community to optimize the Xen implementation.We use our toolkit to analyze performance overheads incurred by networking applications running in Xen VMs. We focus on networking applications since virtualizing network I/O devices is relatively expensive. Our experimental results quantify Xen's performance overheads for network I/O device virtualization in uni- and multi-processor systems. With certain Xen configurations, networking workloads in the Xen environment can suffer significant performance degradation. Our results identify the main sources of this overhead which should be the focus of Xen optimization efforts. We also show how our profiling toolkit was used to uncover and resolve performance bugs that we encountered in our experiments which caused unexpected application behavior.

Abstract: Operating systems are difficult to debug with traditional cyclic debugging. They are non-deterministic; they run for long periods of time; they interact directly with hard-ware devices; and their state is easily perturbed by the act of debugging. This paper describes a time-traveling virtual machine that overcomes many of the difficulties associated with debugging operating systems. Time travel enables a programmer to navigate backward and forward arbitrarily through the execution history of a particular run and to replay arbitrary segments of the past execution. We integrate time travel into a general-purpose debugger to enable a programmer to debug an OS in reverse, implementing commands such as reverse breakpoint, reverse watchpoint, and reverse single step. The space and time overheads needed to support time travel are reasonable for debugging, and movements in time are fast enough to support interactive debugging. We demonstrate the value of our time-traveling virtual machine by using it to understand and fix several OS bugs that are difficult to find with standard debugging tools. Reverse debugging is especially helpful in finding bugs that are fragile due to non-determinism, bugs in device drivers, bugs that require long runs to trigger, bugs that corrupt the stack, and bugs that are detected after the relevant stack frame is popped.

Abstract: Improving security of a processing system may be accomplished by at least one of executing and accessing a suspect file in a sandbox virtual machine.

Abstract: Virtual machines of a virtual data center generate runtime instances with a software image, hardware configuration, management configuration and user/service configuration. Virtual data center resource use is monitored by reference to the management configuration of runtime instances, such as for environmental controls like power, cooling and balancing, or for policy limitations on users, software or hardware. Users or services generate runtime instances of stored virtual machines by reference to the user/service configuration, such as pricing or priority. In one example embodiment, the virtual machine software image comprises an application system preparation file that populates a read only application image common to plural virtual machines. Information unique to each virtual machine with respect to the application is maintained in the user/service configuration of the virtual machine and version information is maintained in the management configuration of the virtual machine. Updates to the application across each virtual machine are performed by updating the read only image or any of its configuration information for hardware configuration, management configuration or user/service configuration.

Abstract: As virtual machines become pervasive users will be able to create, modify and distribute new "machines" with unprecedented ease. This flexibility provides tremendous benefits for users. Unfortunately, it can also undermine many assumptions that today's relatively static security architectures rely on about the number of hosts in a system, their mobility, connectivity, patch cycle, etc. We examine a variety of security problems virtual computing environments give rise to. We then discuss potential directions for changing security architectures to adapt to these demands.

Abstract: In one embodiment, a method comprises executing a plurality of virtual machines on a plurality of nodes of a cluster computing system, wherein at least one application is executed within each of the plurality of virtual machines, generating data that is related to performance of applications in the virtual machines, analyzing, by a management process, the data in view of parameters that encode desired performance levels of applications, and migrating, by the management process, a virtual machine on a first node to a second node of the plurality of nodes in response to the analyzing.

Abstract: We present the sHype hypervisor security architecture and examine in detail its mandatory access control facilities. While existing hypervisor security approaches aiming at high assurance have been proven useful for high-security environments that prioritize security over performance and code reuse, our approach aims at commercial security where near-zero performance overhead, non-intrusive implementation, and usability are of paramount importance. sHype enforces strong isolation at the granularity of a virtual machine, thus providing a robust foundation on which higher software layers can enact finer-grained controls. We provide the rationale behind the sHype design and describe and evaluate our implementation for the Xen open-source hypervisor

Abstract: Another view is that it provides another example of a kernel API. In contrast to other kernel APIs (unix, microkernel, and exokernel), the virtual machine operating system exports as the kernel API the processor API (e.g., the x86 interface). Thus, each program running in user space sees the services offered by a processor, and each program sees its own processor. Of course, we don't want to make a system call for each instruction, and in fact one of the main challenges in virtual machine operation systems is to design the system in such a way that the physical processor executes the virtual processor API directly, at processor speed.

Abstract: This paper describes the evolution of the JikesTM Research Virtual Machine project from an IBM internal research project, called Jalapeno, into an open-source project. After summarizing the original goals of the project, we discuss the motivation for releasing it as an open-source project and the activities performed to ensure the success of the project. Throughout, we highlight the unique challenges of developing and maintaining an open-source project designed specifically to support a research community.

Abstract: This paper describes the architecture of the first implementation of the In-VIGO grid-computing system. The architecture is designed to support computational tools for engineering and science research In Virtual Information Grid Organizations (as opposed to in vivo or in vitro experimental research). A novel aspect of In-VIGO is the extensive use of virtualization technology, emerging standards for grid-computing and other Internet middleware. In the context of In-VIGO, virtualization denotes the ability of resources to support multiplexing, manifolding and polymorphism (i.e. to simultaneously appear as multiple resources with possibly different functionalities). Virtualization technologies are available or emerging for all the resources needed to construct virtual grids which would ideally inherit the above mentioned properties. In particular, these technologies enable the creation of dynamic pools of virtual resources that can be aggregated on-demand for application-specific user-specific grid-computing. This change in paradigm from building grids out of physical resources to constructing virtual grids has many advantages but also requires new thinking on how to architect, manage and optimize the necessary middleware. This paper reviews the motivation for In-VIGO approach, discusses the technologies used, describes an early architecture for In-VIGO that represents a first step towards the end goal of building virtual information grids, and reports on first experiences with the In-VIGO software under development.

Abstract: Virtual machines face significant performance challenges beyond those confronted by traditional static optimizers. First, portable program representations and dynamic language features, such as dynamic class loading, force the deferral of most optimizations until runtime, inducing runtime optimization overhead. Second, modular program representations preclude many forms of whole-program interprocedural optimization. Third, virtual machines incur additional costs for runtime services such as security guarantees and automatic memory management. To address these challenges, vendors have invested considerable resources into adaptive optimization systems in production virtual machines. Today, mainstream virtual machine implementations include substantial infrastructure for online monitoring and profiling, runtime compilation, and feedback-directed optimization. As a result, adaptive optimization has begun to mature as a widespread production-level technology. This paper surveys the evolution and current state of adaptive optimization technology in virtual machines.

Abstract: Systems and methods for applying virtual machines to graphics hardware are provided. In various embodiments of the invention, while supervisory code runs on the CPU, the actual graphics work items are run directly on the graphics hardware and the supervisory code is structured as a graphics virtual machine monitor. Application compatibility is retained using virtual machine monitor (VMM) technology to run a first operating system (OS), such as an original OS version, simultaneously with a second OS, such as a new version OS, in separate virtual machines (VMs). VMM technology applied to host processors is extended to graphics processing units (GPUs) to allow hardware access to graphics accelerators, ensuring that legacy applications operate at full performance. The invention also provides methods to make the user experience cosmetically seamless while running multiple applications in different VMs. In other aspects of the invention, by employing VMM technology, the virtualized graphics architecture of the invention is extended to provide trusted services and content protection.

Abstract: This paper describes the evolution of the JikesTM Research Virtual Machine project from an IBM internal research project, called Jalapeno, into an open-source project. After summarizing the original goals of the project, we discuss the motivation for releasing it as an open-source project and the activities performed to ensure the success of the project. Throughout, we highlight the unique challenges of developing and maintaining an open-source project designed specifically to support a research community.

Abstract: Despite significant progress in the development of Grid infrastructure, the provisioning of a customized and controllable remote execution environment remains an open issue. This paper introduces the concept of a virtual workspace, a configurable execution environment that can be created and managed as a first-class entity to reflect client requirements. Such workspaces can be dynamically deployed on a variety of resources decoupling the notion of environment and resource. We show how virtual workspaces fit into the Grid architecture, present an example implementation using virtual machines, and discuss our initial experiences using this system in practice and with applications.

Abstract: Sensor networks are being deployed at massive scales, containing a range of platforms. Programming paradigms for sensor networks should meet the attendant challenges of scale and heterogeneity. Researchers have considered virtual machines as a means to address these challenges. However, in order to satisfy the resource limitations of sensor nodes, they export only a minimal set of services to the application programmer. This makes applications of even moderate complexity difficult to implement. We present VMSTAR --- a framework for building resource-efficient virtual machines that scale and export comprehensive service suites on a per-application basis. We advocate the use of fine-grained software synthesis to build resource-efficient system software, and facilitate both application changes and system software upgrades at runtime through an efficient incremental update scheme. We have used our framework to build virtual machines on the Mica platform and describe how virtual machines are effective in meeting the difficult demands of heterogeneity and reprogrammability.

Abstract: A method (and system) for managing a distributed-memory parallel application running on multiple servers, includes dynamically moving a plurality of executable program components, where each of the plurality of executable program components are running on one of a plurality of virtual machines, using migration of the virtual machines between physical servers. The load balancing is operated based on a workload of each of the virtual machines and servers, where a virtual machine, or a plurality of virtual machines, are transferred to balance the workload between each of the servers.

Abstract: Virtualization technologies encompass a variety of mechanisms and techniques used to address computer system problems such as security, performance, and reliability by decoupling the architecture and user-perceived behavior of hardware and software resources from their physical implementation.

Abstract: The goal of this short paper is twofold: 1) it briefly describes a new performance monitoring tool, XenMon, that we built for the Xen-based virtual environment, and 2) it presents a performance case study that demonstrates and explains how different metrics reported by XenMon can be used in gaining insight into an application’s performance and its resource usage/requirements, especially in the case of I/O intensive applications.

Abstract: The invention relates to a method, system and apparatus for managing a small business' advertising. More specifically, the system creates and administers a virtual online world accessible to users (players) within a virtual environment. A player interacts with various elements of the virtual environment and during those interactions the advertising is displayed to the user. To subscribe to the virtual environment, a player provides user information through a registration process to create a user profile. The system selects and displays advertisements that are correlated to a given user. The correlation between advertisement and user in one embodiment of the invention is based on a user's zip code. Further, in order to facilitate the quick adoption of the system among small business owners, a fundraising paradigm is implemented. More specifically, people volunteer to sell advertising opportunities within a virtual environment in exchange for a share of sales revenues.

Abstract: A system and method for accelerating input/output (IO) access operation on a virtual machine, The method comprises providing a smart IO device that includes an unrestricted command queue (CQ) and a plurality of restricted CQs and allowing a guest domain to directly configure and control IO resources through a respective restricted CQ, the IO resources allocated to the guest domain. In preferred embodiments, the allocation of IO resources to each guest domain is performed by a privileged virtual switching element. In some embodiments, the smart IO device is a HCA and the privileged virtual switching element is a Hypervisor.

Abstract: We describe a between-subjects experiment that compared four different methods of travel and their effect on cognition and paths taken in an immersive virtual environment (IVE). Participants answered a set of questions based on Crook's condensation of Bloom's taxonomy that assessed their cognition of the IVE with respect to knowledge, understanding and application, and higher mental processes. Participants also drew a sketch map of the IVE and the objects within it. The users' sense of presence was measured using the Steed-Usoh-Slater presence questionnaire. The participants' position and head orientation were automatically logged during their exposure to the virtual environment. These logs were later used to create visualizations of the paths taken. Path analysis, such as exploring the overlaid path visualizations and dwell data information, revealed further differences among the travel techniques. Our results suggest that, for applications where problem solving and evaluation of information is important or where opportunity to train is minimal, then having a large tracked space so that the participant can walk around the virtual environment provides benefits over common virtual travel techniques.

Abstract: A method of virtualizing memory through shadow page tables that cache translations from multiple guest address spaces in a virtual machine includes a software version of a hardware tagged translation look-aside buffer. Edits to guest page tables are detected by intercepting the creation of guest-writable mappings to guest page tables with translations cached in shadow page tables. The affected cached translations are marked as stale and purged upon an address space switch or an indiscriminate flush of translations by the guest. Thereby, non-stale translations remain cached but stale translations are discarded. The method includes tracking the guest-writable mappings to guest page tables, deferring discovery of such mappings to a guest page table for the first time until a purge of all cached translations when the number of untracked guest page tables exceeds a threshold, and sharing shadow page tables between shadow address spaces and between virtual processors.

Abstract: We are developing Virtuoso, u system ,for distributed computing using virtual machines (VMs). Virtuoso must be uble to mix batch und interactive VMs on the same physical hardwure, while satisfiing constraint on re- sponsiveness und compute rates for each workload. VSched is the component of Virtuoso that provides this capability. VSched is an entirely user-level tool that interacts with the stock Linux kernel running below any type-11 virtual machine monitor to schedule VMs (indeed, any process) using a periodic real-time scheduling model. This abstraction allows compute rate and responsivness constraints to be straightforwardly described using a period und a slice within the period, and it allows,for just and simple admission control. This paper makes the case,for periodic real-time scheduling for VM-based computing environments, and then describes and evaluate.s VSched. It also applies VSched to scheduling parallel worklouds, showing that it can help a BSP application maintain a fixed stable performance despite externally caused loud imbalance.