Performance analysis of selected hypervisors (Virtual Machine Monitors - VMMs)

Virtualization of operating systems and network infrastructure plays an important role in current IT projects. With the number of services running on different hardware resources it is easy to provide availability, security and efficiency using virtualizers. All virtualization vendors claim that their hypervisor (virtual machine monitor - VMM) is better than their competitors. In this paper we evaluate performance of different solutions: proprietary software products (Hyper-V, ESXi, OVM, VirtualBox), and open source (Xen). We are using standard benchmark tools to compare efficiency of main hardware components, i.e. CPU (nbench), NIC (netperf), storage (Filebench), memory (ramspeed). Results of each tests are presented

Gestão e engenharia de CAP na nuvem híbrida

Doutoramento em InformáticaThe evolution and maturation of Cloud Computing created an opportunity for the emergence of new Cloud applications. High-performance Computing, a complex problem solving class, arises as a new business consumer by taking advantage of the Cloud premises and leaving the expensive datacenter management and difficult grid development. Standing on an advanced maturing phase, today’s Cloud discarded many of its drawbacks, becoming more and more efficient and widespread. Performance enhancements, prices drops due to massification and customizable services on demand triggered an emphasized attention from other markets. HPC, regardless of being a very well established field, traditionally has a narrow frontier concerning its deployment and runs on dedicated datacenters or large grid computing. The problem with common placement is mainly the initial cost and the inability to fully use resources which not all research labs can afford. The main objective of this work was to investigate new technical solutions to allow the deployment of HPC applications on the Cloud, with particular emphasis on the private on-premise resources – the lower end of the chain which reduces costs. The work includes many experiments and analysis to identify obstacles and technology limitations. The feasibility of the objective was tested with new modeling, architecture and several applications migration. The final application integrates a simplified incorporation of both public and private Cloud resources, as well as HPC applications scheduling, deployment and management. It uses a well-defined user role strategy, based on federated authentication and a seamless procedure to daily usage with balanced low cost and performance.O desenvolvimento e maturação da Computação em Nuvem abriu a janela de oportunidade para o surgimento de novas aplicações na Nuvem. A Computação de Alta Performance, uma classe dedicada à resolução de problemas complexos, surge como um novo consumidor no Mercado ao aproveitar as vantagens inerentes à Nuvem e deixando o dispendioso centro de computação tradicional e o difícil desenvolvimento em grelha. Situando-se num avançado estado de maturação, a Nuvem de hoje deixou para trás muitas das suas limitações, tornando-se cada vez mais eficiente e disseminada. Melhoramentos de performance, baixa de preços devido à massificação e serviços personalizados a pedido despoletaram uma atenção inusitada de outros mercados. A CAP, independentemente de ser uma área extremamente bem estabelecida, tradicionalmente tem uma fronteira estreita em relação à sua implementação. É executada em centros de computação dedicados ou computação em grelha de larga escala. O maior problema com o tipo de instalação habitual é o custo inicial e o não aproveitamento dos recursos a tempo inteiro, fator que nem todos os laboratórios de investigação conseguem suportar. O objetivo principal deste trabalho foi investigar novas soluções técnicas para permitir o lançamento de aplicações CAP na Nuvem, com particular ênfase nos recursos privados existentes, a parte peculiar e final da cadeia onde se pode reduzir custos. O trabalho inclui várias experiências e análises para identificar obstáculos e limitações tecnológicas. A viabilidade e praticabilidade do objetivo foi testada com inovação em modelos, arquitetura e migração de várias aplicações. A aplicação final integra uma agregação de recursos de Nuvens, públicas e privadas, assim como escalonamento, lançamento e gestão de aplicações CAP. É usada uma estratégia de perfil de utilizador baseada em autenticação federada, assim como procedimentos transparentes para a utilização diária com um equilibrado custo e performance

A Dynamic Resource Manager with Effective Resource Isolation Based on Workload Types in Virtualized Cloud Computing Environments

To use computing resources for processing parallel algorithms on demand, cloud computing has been widely used since it is able to scale in response to load increases and decreases. Typically, cloud computing providers offer virtual machines to cloud users with static configurations, and these configurations are not changed until virtual machines are shutting down. To accelerate parallel processing computations in cloud computing environments, we design and implement a dynamic resource manager by isolating resources based on workload types. To avoid unnecessary context switching and increase CPUs affinity, our dynamic resource manager determines whether vCPU to physical CPU core pinning is required. If so, the VM’s vCPUs are pinned by our dynamic resource manager, which can guarantee the resource and performance isolation. With our proposed resource manager for virtual machines, we can achieve a performance boost and load balancing at the same time. Performance results show that our proposed method outperforms the default scheduler of Xen about 36.2% by reducing the number of context switching for VMs

The Design, Implementation, and Evaluation of Software and Architectural Support for ARM Virtualization

The ARM architecture is dominating in the mobile and embedded markets and is making an upwards push into the server and networking markets where virtualization is a key technology. Similar to x86, ARM has added hardware support for virtualization, but there are important differences between the ARM and x86 architectural designs. Given two widely deployed computer architectures with different approaches to hardware virtualization support, we can evaluate, in practice, benefits and drawbacks of different approaches to architectural support for virtualization. This dissertation explores new approaches to combining software and architectural support for virtualization with a focus on the ARM architecture and shows that it is possible to provide virtualization services an order of magnitude more efficiently than traditional implementations. First, we investigate why the ARM architecture does not meet the classical requirements for virtualizable architectures and present an early prototype of KVM for ARM, a hypervisor using lightweight paravirtualization to run VMs on ARM systems without hardware virtualization support. Lightweight paravirtualization is a fully automated approach which replaces sensitive instructions with privileged instructions and requires no understanding of the guest OS code. Second, we introduce split-mode virtualization to support hosted hypervisor designs using ARM's architectural support for virtualization. Different from x86, the ARM virtualization extensions are based on a new hypervisor CPU mode, separate from existing CPU modes. This separate hypervisor CPU mode does not support running existing unmodified OSes, and therefore hosted hypervisor designs, in which the hypervisor runs as part of a host OS, do not work on ARM. Split-mode virtualization splits the execution of the hypervisor such that the host OS with core hypervisor functionality runs in the existing kernel CPU mode, but a small runtime runs in the hypervisor CPU mode and supports switching between the VM and the host OS. Split-mode virtualization was used in KVM/ARM, which was designed from the ground up as an open source project and merged in the mainline Linux kernel, resulting in interesting lessons about translating research ideas into practice. Third, we present an in-depth performance study of 64-bit ARMv8 virtualization using server hardware and compare against x86. We measure the performance of both standalone and hosted hypervisors on both ARM and x86 and compare their results. We find that ARM hardware support for virtualization can enable faster transitions between the VM and the hypervisor for standalone hypervisors compared to x86, but results in high switching overheads for hosted hypervisors compared to both x86 and to standalone hypervisors on ARM. We identify a key reason for high switching overhead for hosted hypervisors being the need to save and restore kernel mode state between the host OS kernel and the VM kernel. However, standalone hypervisors such as Xen, cannot leverage their performance benefit in practice for real application workloads. Other factors related to hypervisor software design and I/O emulation play a larger role in overall hypervisor performance than low-level interactions between the hypervisor and the hardware. Fourth, realizing that modern hypervisors rely on running a full OS kernel, the hypervisor OS kernel, to support their hypervisor functionality, we present a new hypervisor design which runs the hypervisor and its hypervisor OS kernel in ARM's separate hypervisor CPU mode and avoids the need to multiplex kernel mode CPU state between the VM and the hypervisor. Our design benefits from new architectural features, the virtualization host extensions (VHE), in ARMv8.1 to avoid modifying the hypervisor OS kernel to run in the hypervisor CPU mode. We show that the hypervisor must be co-designed with the hardware features to take advantage of running in a separate CPU mode and implement our changes to KVM/ARM. We show that running the hypervisor OS kernel in a separate CPU mode from the VM and taking advantage of ARM's ability to quickly switch between the VM and hypervisor results in an order of magnitude reduction in overhead for important virtualization microbenchmarks and reduces the overhead of real application workloads by more than 50%

Tutkimus virtualisoinnista ja energiatehokkuudesta Linuxilla

Virtualization has in recent years risen in popularity to the extent of changing the way information technology infrastructure in enterprise data centers is built. Once known as a technique to achieve time sharing between processes, virtualization now offers flexibility in resource usage and software deployment, security, and energy savings by consolidation of many virtualized servers into a single physical one. However, in its modern form, virtualization is still a relatively young technology. There are many studies regarding the performance of different virtualization technologies, but only a few emphasize energy efficiency. When information technology service providers invest in more server hardware, their energy expenses also rise. As optimization for energy efficiency becomes more and more important, possible power consumption overhead caused by virtualization will be an important factor when setting up virtualized servers. In this thesis we studied virtualization using Linux with focus on energy efficiency. We conducted sets of performance tests while measuring power consumption, and assessed how virtualization affects energy efficiency. The tests included synthetic tests and more practical web server tests, with single and multiple virtual machines. We tested various configurations to find out what one should generally note when building a virtualized environment with focus on energy efficiency. All of this was done using various virtualization technologies to find out their differences regarding energy efficiency. The tested technologies were KVM, Xen, and vSphere Hypervisor. With respect to energy efficiency or performance, we observed differences in virtualization technologies, and the same technology was not always the best in every situation. We found KVM to offer good energy efficiency, and Xen to have some trouble with recent Linux versions. In web server tests, the use of paravirtualization had almost no effect on power consumption. Processor performance states affected performance and energy efficiency. Power consumption had a tendency to be generally high with bare-metal virtual machine monitors Xen and vSphere Hypervisor. More research with a wider selection of test hardware and software is required to better define the setups and situations where this power consumption trend and the possible effect of paravirtualization on energy efficiency are observable

Virtualization of Micro-architectural Components Using Software Solutions

Cloud computing has become a dominant computing paradigm in the information technology industry due to its flexibility and efficiency in resource sharing and management. The key technology that enables cloud computing is virtualization. Essential requirements in a virtualized system where several virtual machines (VMs) run on a same physical machine include performance isolation and predictability. To enforce these properties, the virtualization software (called the hypervisor) must find a way to divide physical resources (e.g., physical memory, processor time) of the system and allocate them to VMs with respect to the amount of virtual resources defined for each VM. However, modern hardware have complex architectures and some microarchitectural-level resources such as processor caches, memory controllers, interconnects cannot be divided and allocated to VMs. They are globally shared among all VMs which compete for their use, leading to contention. Therefore, performance isolation and predictability are compromised. In this thesis, we propose software solutions for preventing unpredictability in performance due to micro-architectural components. The first contribution is called Kyoto, a solution to the cache contention issue, inspired by the polluters pay principle. A VM is said to pollute the cache if it provokes significant cache replacements which impact the performance of other VMs. Henceforth, using the Kyoto system, the provider can encourage cloud users to book pollution permits for their VMs. The second contribution addresses the problem of efficiently virtualizing NUMA machines. The major challenge comes from the fact that the hypervisor regularly reconfigures the placement of a VM over the NUMA topology. However, neither guest operating systems (OSs) nor system runtime libraries (e.g., HotSpot) are designed to consider NUMA topology changes at runtime, leading end user applications to unpredictable performance. We presents eXtended Para-Virtualization (XPV), a new principle to efficiently virtualize a NUMA architecture. XPV consists in revisiting the interface between the hypervisor and the guest OS, and between the guest OS and system runtime libraries so that they can dynamically take into account NUMA topology changes