Virtualization services: scalable methods for virtualizing multicore systems

Multi-core technology is bringing parallel processing capabilities from servers to laptops and even handheld devices. At the same time, platform support for system virtualization is making it easier to consolidate server and client resources, when and as needed by applications. This consolidation is achieved by dynamically mapping the virtual machines on which applications run to underlying physical machines and their processing cores. Low cost processor and I/O virtualization methods efficiently scaled to different numbers of processing cores and I/O devices are key enablers of such consolidation. This dissertation develops and evaluates new methods for scaling virtualization functionality to multi-core and future many-core systems. Specifically, it re-architects virtualization functionality to improve scalability and better exploit multi-core system resources. Results from this work include a self-virtualized I/O abstraction, which virtualizes I/O so as to flexibly use different platforms' processing and I/O resources. Flexibility affords improved performance and resource usage and most importantly, better scalability than that offered by current I/O virtualization solutions. Further, by describing system virtualization as a service provided to virtual machines and the underlying computing platform, this service can be enhanced to provide new and innovative functionality. For example, a virtual device may provide obfuscated data to guest operating systems to maintain data privacy; it could mask differences in device APIs or properties to deal with heterogeneous underlying resources; or it could control access to data based on the ``trust' properties of the guest VM. This thesis demonstrates that extended virtualization services are superior to existing operating system or user-level implementations of such functionality, for multiple reasons. First, this solution technique makes more efficient use of key performance-limiting resource in multi-core systems, which are memory and I/O bandwidth. Second, this solution technique better exploits the parallelism inherent in multi-core architectures and exhibits good scalability properties, in part because at the hypervisor level, there is greater control in precisely which and how resources are used to realize extended virtualization services. Improved control over resource usage makes it possible to provide value-added functionalities for both guest VMs and the platform. Specific instances of virtualization services described in this thesis are the network virtualization service that exploits heterogeneous processing cores, a storage virtualization service that provides location transparent access to block devices by extending the functionality provided by network virtualization service, a multimedia virtualization service that allows efficient media device sharing based on semantic information, and an object-based storage service with enhanced access control.Ph.D.Committee Chair: Schwan, Karsten; Committee Member: Ahamad, Mustaq; Committee Member: Fujimoto, Richard; Committee Member: Gavrilovska, Ada; Committee Member: Owen, Henry; Committee Member: Xenidis, Jim

Performance analysis and design of iSCSI over wireless network

Master'sMASTER OF ENGINEERIN

Dynamic contention management for distributed applications

PhD ThesisDistributed applications often make use of replicated state to afford a greater level of availability and throughput. This is achieved by allowing individual processes to progress without requiring prior synchronisation. This approach, termed optimistic replication, results in divergent replicas that must be reconciled to achieve an overall consistent state. Concurrent operations to shared objects in the replicas result in conflicting updates that require reconciliatory action to rectify. This typically takes the form of compensatory execution or simply undoing and rolling back client state. When considering user interaction with the application, there exists relationships and intent in the ordering and execution of these operations. The enactment of reconciliation that determines one action as conflicted may have far reaching implications with regards to the user’s original intent. In such scenarios, the compensatory action applied to a conflict may require previous operations to also be undone or compensated such that the user’s intent is maintained. Therefore, an ability to manage the contention to the shared data across the distributed application to pre-emptively lower conflicts resulting from these infringements is desirable. The aim is to not hinder throughput, achieved from the weaker consistency model known as eventual consistency. In this thesis, a model is presented for a contention management framework that schedules access using the expected execution inherent in the application domain to best inform the contention manager. A backoff scheme is employed to create an access schedule, preserving user intent for applications that require this high level of maintenance for user actions. By using such an approach, this results in a performance improvement seen in the reduction of the overall number of conflicts, while also improving overall system throughput. This thesis describes how the contention management scheme operates and, through experimentation, the performance benefits received

Fifth NASA Goddard Conference on Mass Storage Systems and Technologies

This document contains copies of those technical papers received in time for publication prior to the Fifth Goddard Conference on Mass Storage Systems and Technologies held September 17 - 19, 1996, at the University of Maryland, University Conference Center in College Park, Maryland. As one of an ongoing series, this conference continues to serve as a unique medium for the exchange of information on topics relating to the ingestion and management of substantial amounts of data and the attendant problems involved. This year's discussion topics include storage architecture, database management, data distribution, file system performance and modeling, and optical recording technology. There will also be a paper on Application Programming Interfaces (API) for a Physical Volume Repository (PVR) defined in Version 5 of the Institute of Electrical and Electronics Engineers (IEEE) Reference Model (RM). In addition, there are papers on specific archives and storage products

Systems Support for Trusted Execution Environments

Cloud computing has become a default choice for data processing by both large corporations and individuals due to its economy of scale and ease of system management. However, the question of trust and trustoworthy computing inside the Cloud environments has been long neglected in practice and further exacerbated by the proliferation of AI and its use for processing of sensitive user data. Attempts to implement the mechanisms for trustworthy computing in the cloud have previously remained theoretical due to lack of hardware primitives in the commodity CPUs, while a combination of Secure Boot, TPMs, and virtualization has seen only limited adoption. The situation has changed in 2016, when Intel introduced the Software Guard Extensions (SGX) and its enclaves to the x86 ISA CPUs: for the first time, it became possible to build trustworthy applications relying on a commonly available technology. However, Intel SGX posed challenges to the practitioners who discovered the limitations of this technology, from the limited support of legacy applications and integration of SGX enclaves into the existing system, to the performance bottlenecks on communication, startup, and memory utilization. In this thesis, our goal is enable trustworthy computing in the cloud by relying on the imperfect SGX promitives. To this end, we develop and evaluate solutions to issues stemming from limited systems support of Intel SGX: we investigate the mechanisms for runtime support of POSIX applications with SCONE, an efficient SGX runtime library developed with performance limitations of SGX in mind. We further develop this topic with FFQ, which is a concurrent queue for SCONE's asynchronous system call interface. ShieldBox is our study of interplay of kernel bypass and trusted execution technologies for NFV, which also tackles the problem of low-latency clocks inside enclave. The two last systems, Clemmys and T-Lease are built on a more recent SGXv2 ISA extension. In Clemmys, SGXv2 allows us to significantly reduce the startup time of SGX-enabled functions inside a Function-as-a-Service platform. Finally, in T-Lease we solve the problem of trusted time by introducing a trusted lease primitive for distributed systems. We perform evaluation of all of these systems and prove that they can be practically utilized in existing systems with minimal overhead, and can be combined with both legacy systems and other SGX-based solutions. In the course of the thesis, we enable trusted computing for individual applications, high-performance network functions, and distributed computing framework, making a <vision of trusted cloud computing a reality

Adaptive Caching of Distributed Components

Die Zugriffslokalität referenzierter Daten ist eine wichtige Eigenschaft verteilter Anwendungen. Lokales Zwischenspeichern abgefragter entfernter Daten (Caching) wird vielfach bei der Entwicklung solcher Anwendungen eingesetzt, um diese Eigenschaft auszunutzen. Anschliessende Zugriffe auf diese Daten können so beschleunigt werden, indem sie aus dem lokalen Zwischenspeicher bedient werden. Gegenwärtige Middleware-Architekturen bieten dem Anwendungsprogrammierer jedoch kaum Unterstützung für diesen nicht-funktionalen Aspekt. Die vorliegende Arbeit versucht deshalb, Caching als separaten, konfigurierbaren Middleware-Dienst auszulagern. Durch die Einbindung in den Softwareentwicklungsprozess wird die frühzeitige Modellierung und spätere Wiederverwendung caching-spezifischer Metadaten gewährleistet. Zur Laufzeit kann sich das entwickelte System außerdem bezüglich der Cachebarkeit von Daten adaptiv an geändertes Nutzungsverhalten anpassen.Locality of reference is an important property of distributed applications. Caching is typically employed during the development of such applications to exploit this property by locally storing queried data: Subsequent accesses can be accelerated by serving their results immediately form the local store. Current middleware architectures however hardly support this non-functional aspect. The thesis at hand thus tries outsource caching as a separate, configurable middleware service. Integration into the software development lifecycle provides for early capturing, modeling, and later reuse of cachingrelated metadata. At runtime, the implemented system can adapt to caching access characteristics with respect to data cacheability properties, thus healing misconfigurations and optimizing itself to an appropriate configuration. Speculative prefetching of data probably queried in the immediate future complements the presented approach

Sixth Goddard Conference on Mass Storage Systems and Technologies Held in Cooperation with the Fifteenth IEEE Symposium on Mass Storage Systems

This document contains copies of those technical papers received in time for publication prior to the Sixth Goddard Conference on Mass Storage Systems and Technologies which is being held in cooperation with the Fifteenth IEEE Symposium on Mass Storage Systems at the University of Maryland-University College Inn and Conference Center March 23-26, 1998. As one of an ongoing series, this Conference continues to provide a forum for discussion of issues relevant to the management of large volumes of data. The Conference encourages all interested organizations to discuss long term mass storage requirements and experiences in fielding solutions. Emphasis is on current and future practical solutions addressing issues in data management, storage systems and media, data acquisition, long term retention of data, and data distribution. This year's discussion topics include architecture, tape optimization, new technology, performance, standards, site reports, vendor solutions. Tutorials will be available on shared file systems, file system backups, data mining, and the dynamics of obsolescence

Enhancing the programmability and energy efficiency of storage in hpc and virtualized environments

Mención Internacional en el título de doctorA decade ago computing systems hit a clock and power ceiling that places the energetic challenge among the most relevant issues in High Performance Computing (HPC). Motivated by the fact that computation is increasingly becoming cheaper than data movement in terms of power, our work studies and optimizes data movement across different levels of the software stack. We propose novel methodologies for analyzing, modeling, and optimizing the energy efficiency of data movement. More precisely, we propose methodologies to enhance the understanding of power consumption in the software I/O stack, and optimize the I/O energy efficiency in the operating system’s I/O stack, low-level CPU device drivers, and virtualized environments. Our experimental results show that through the understanding of the different operating system layers and their interaction, it is possible to develop novel coordination techniques that optimize the energy consumption and increase performance of I/O workloads. First, we develop a methodology for data collection, power and performance characterization, and modeling power usage in the I/O stack. Our work presents a detailed study of power and energy usage across all system components during various I/O-intensive workloads. We propose a data gathering methodology that combines software and hardware-based instrumentation in order to study I/O data movement, and develop novel power prediction models employing data analysis techniques. Second, this thesis presents novel CPU-level optimizations that improve the energy efficiency of I/O workloads. We address two issues present in modern processors: thermal imbalance causing performance variation and an inefficient use of CPU resources during I/O workloads. We develop novel techniques for power optimization and thermal efficiency through cross-layer coordination of CPU and I/O management. Third, we also focus on optimizing data sharing among virtual domains. In our work we refer to this as virtualized data sharing, which mainly differs from existing solutions by coordinating data flows through the software I/O stack. We develop a virtualized data sharing solution in order to reduce data movement among virtual environments, introducing new abstractions and mechanisms to more efficiently coordinate storage I/O.Hace una década, los computadores alcanzaron el límite físico de la frecuencia y potencia disipada, estableciendo el consumo energético como uno de los principales obstáculos en el campo de la computación de alto rendimiento. Motivados por el hecho de que la computación resulta cada vez menos costosa que el movimiento de datos en términos de energía, nuestro trabajo estudia y optimiza el movimiento de datos en varios niveles de la arquitectura software. En este trabajo proponemos nuevas metodologías para analizar, modelar y optimizar la eficiencia energética del movimiento de datos. Concretamente, proponemos metodologías para mejorar el análisis del consumo de potencia en la arquitectura software de E/S, así como optimizar la eficiencia energética de: la pila de E/S del sistema operativo, controladores de la CPU y entornos virtuales de E/S. Los resultados experimentales muestran que, mediante la comprensión de la interacción de las capas del sistema operativo, es posible desarrollar nuevas técnicas de coordinación que optimicen el consumo energético e incrementen el rendimiento de las cargas de trabajo de E/S. En primer lugar desarrollamos una metodología para la recolección de datos y la caracterización del rendimiento y consumo de potencia en la pila de E/S. Nuestro trabajo presenta un estudio detallado del consumo energético y de potencia de cada uno de los componentes del sistema durante la ejecución de cargas de trabajo de E/S. Concretamente proponemos una metodología de captura de datos que combina instrumentación hardware y software para estudiar el movimiento de datos, con el fin de desarrollar nuevos modelos de predicción de consumo empleando técnicas de análisis de datos. En segundo lugar, esta Tesis Doctoral presentamos nuevas optimizaciones a nivel de CPU que mejoran la eficiencia energética de las cargas de trabajo de E/S. Para ello consideramos dos problemas fundamentales en los procesadores modernos: el desequilibrio térmico que causa variablidad de rendimiento y el uso ineficiente de los recursos de la CPU durante cargas de trabajo de E/S. Además desarrollamos nuevas técnicas que optimizan la eficiencia energética a través de la coordinación entre las distintas capas del sistema operativo que gestionan CPU y la E/S. En tercer lugar, también centramos este trabajo en la optimización del intercambio de datos entre dominios virtuales. En nuestro trabajo nos referimos a esto como el intercambio de datos virtualizado, que se diferencia principalmente de las soluciones existentes mediante la coordinación de los flujos de datos mediante la cooperación entre distintos dominios virtuales. Para ello desarrollamos una solución de intercambio de datos que minimiza la copia de datos con el fin de reducir el movimiento de datos, e introducimos nuevas abstracciones y mecanismos para coordinar de manera más eficiente el almacenamiento de E/S en entornos virtuales.Programa Oficial de Doctorado en Ciencia y Tecnología InformáticaPresidente: Laurent Lefevre.- Vocal: Arturo González Escriban