Problems of Wireless Sensor Networks (WSN) caused in the laboratory are predictable, and easy to resolve. While in the deployment and management phases, a number of factors in the environment raise more problems that ...
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VM (virtual machine) scheduling is a fundamental topic of virtualization, and fairness is its important design goal. Most VMMs (virtual machine monitor) provide PS (proportional share) schedulers. A PS scheduler assig...
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VM (virtual machine) scheduling is a fundamental topic of virtualization, and fairness is its important design goal. Most VMMs (virtual machine monitor) provide PS (proportional share) schedulers. A PS scheduler assign a weight to every VM to declare the computational resource requirement, and VM is allocated CPU cycles proportional to weight. CPU-affinity is a property of VCPU (virtual CPU) to describe which PCPUs (physical CPU) it can run on. However, current definition of weight does not collaborate well with CPU-affinity. It behaves as if all PCPUs are available to all VMs. We expose the issue by using Xen’s Credit scheduler, and show that CPU cycles can be fairly allocated to VMs in the default free-mapping case (no affinity restriction), but not so in restricted-mapping cases (when affinities are configured). This fairness issue makes it necessary to extend the meaning of weight, so as to reflect the resource requirements in all cases. In this paper we reconcile the meaning of a domain’s weight with CPU-affinity, and improve Credit scheduler as an affinity-aware one. Experimental results show that our affinity-aware proportional share scheduler (named Credit-APS scheduler) brings a good fairness both in free-mapping and restricted-mapping cases.
With the rapid development of virtualization technology as well as the good performance of computer hardware, virtual machine is beginning to gradually increase the performance of display to meet the needs of desktop ...
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With the rapid development of virtualization technology as well as the good performance of computer hardware, virtual machine is beginning to gradually increase the performance of display to meet the needs of desktop users. However, there is a difference between the display mechanism in the virtual environment and the traditional environment. At present, more is focused on how to effectively and pertinently measure and assess the performance of display in virtualization environment. Taking consideration of the characteristics of display in the virtual environment, the virtual machine display performance evaluation system has following advantages: it can select a representative workload running on the VM in Domain U; make use of Tracing and Instrumentation to insert the record in the kernel of VM; log the relevant information; and then finally draw the performance-related parameters by the analysis of the recorder. This paper mainly depicts the underlying implementation details of the virtual display system in Xen and analyzes the display principle of Xen-based virtual machine. It also proposes a display latency performance model in Xen environment, which is named Vdismodel by verifying the reasonableness of the Vdismodel through a series of experiments and comparing the theoretical data and the measured data which are accessed by the virtual machine system performance evaluation.
A virtual cluster consists of a multitude of virtual machines and software components that are doomed to fail eventually. In many environments, such failures can result in unanticipated, potentially devastating failur...
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Virtualization technology improves the resource utilization, but also raises the probability of resource contention. Thus, it arises one problem, namely how about performance isolation among VMs. To answer the questio...
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Virtualization technology improves the resource utilization, but also raises the probability of resource contention. Thus, it arises one problem, namely how about performance isolation among VMs. To answer the question, benchmarks are highly required to evaluate performance isolation. However, few benchmarks to give solutions to the problem are available. Especially, there does not exist a micro-benchmark to measure how the performance of individual primitive operations varies with the type of misbehavior. In the paper, we present VITS - a micro-benchmark to evaluate the performance isolation of virtualization system. VITS Test Suite can test both software and hardware performance isolation. It is mainly consisted of six interference programs, which respectively test the performance isolation of cache, memory bandwidth, memory space, CPU, network and disk. VITS Test Suite provides results for user to analyze the performance isolation problem of the virtualization system along with the underlying hardware. Besides, we test Xen using VITS test suit. The experimental results show that, the cache, memory and disk performance isolation still have some big weak points to improve, in other words, the current virtualization system Xen is still unfair in fine-grained resource share.
As the degree of virtualization is growing considerably, improving performance of virtual machine environments motivates deeper investigation of the internal processes and performance implications of virtualization. S...
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As the degree of virtualization is growing considerably, improving performance of virtual machine environments motivates deeper investigation of the internal processes and performance implications of virtualization. Several tools are currently available to help analyze performance in virtual machine environments. However, all of these cannot support users to add their own trace information. In this paper, we present Xenrelay, a unified, efficient, and simple mechanism for transferring large amounts of data from guest domain kernel to privileged domain user-space. Xenrelay allows users (who trace subsystems of guest domain to analyze performance) to record and fast relay data between domains. We provide a case of Xenrelay's value in revealing behavior of virtualization. We build a block trace toolkit (using Xenrelay as an engine). This toolkit is used to track the block I/O virtualization procedures and evaluates overheads in the Xen environment. Our trace results identify that the main delay is the time of request transmission and block device operation. Besides, the results reveal impact of the I/O schedules on the disk performance.
Transactional memory (TM) is a parallel programming concept. Existing consistency protocols in distributed transactional memory system consume too much bandwidth and bring high latency. In this paper, we propose our T...
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Transactional memory (TM) is a parallel programming concept. Existing consistency protocols in distributed transactional memory system consume too much bandwidth and bring high latency. In this paper, we propose our Transaction Memory Consistency Protocol (TMCP), and point the new features compared to the current protocols. After formulating our model and analyzing the performance, we found both too much and too little execution time will cause more conflicts, given that the execution time of transaction population follows Gamma distribution. We indicate that it is important to adjust the execution time to a reasonable value to improve performance.
With the popularity of virtualization, the problem that how to manage hundreds even thousands of virtual machines running on multiple physical computing nodes becomes important. Current virtual machine management syst...
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With the popularity of virtualization, the problem that how to manage hundreds even thousands of virtual machines running on multiple physical computing nodes becomes important. Current virtual machine management systems only can obtain basic information of virtual machines and execute simple operations on them, such as start, reboot and shutdown. In this paper, we design a virtual machine management approach based on agent service. Agent service can provide detail running status information inside virtual machines. It also has been a bridge for host machines and virtual machines to interact with each other. Agent service is designed to automatically start when virtual machine boots up. By agent service we can get real-time information about virtual machines. We evaluate monitoring overhead and the performance of batch operations when using agent. The experimental results show that agent mechanism outperforms methods using Libvirt or VMware tools.
grid is susceptible to a number of software and hardware failures, so a deep understanding of and modeling the grid resource failures are a challenge and have significant influence on grid researching. However, due to...
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grid is susceptible to a number of software and hardware failures, so a deep understanding of and modeling the grid resource failures are a challenge and have significant influence on grid researching. However, due to various reasons such as commercial secret and security, it is difficult to obtain real historical logs of grids. Therefore, an accurate model of resource failures is critically useful. In the paper, through analyzing the grid log data, we detail the suitability of three potential statistical distributions for each data set: Weibull, Zipf's law and Pareto. Then, this paper develops a grid resource failure simulator. Finally, with the different failure patterns generated by the failure simulator, the paper evaluates several common scheduling algorithms used in gridsystems.
A virtual cluster consists of a multitude of virtual machines and software components that are doomed to fail eventually. In many environments, such failures can result in unanticipated, potentially devastating failur...
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A virtual cluster consists of a multitude of virtual machines and software components that are doomed to fail eventually. In many environments, such failures can result in unanticipated, potentially devastating failure behavior and in service unavailability. The ability of failover is essential to the virtual cluster's availability, reliability, and manageability. Most of the existing methods have several common disadvantages: requiring modifications to the target processes or their OSes, which is usually error prone and sometimes impractical; only targeting at taking checkpoints of processes, not whole entire OS images, which limits the areas to be applied. In this paper we present VirtCFT, an innovative and practical system of fault tolerance for virtual cluster. VirtCFT is a system-level, coordinated distributed checkpointing fault tolerant system. It coordinates the distributed VMs to periodically reach the globally consistent state and take the checkpoint of the whole virtual cluster including states of CPU, memory, disk of each VM as well as the network communications. When faults occur, VirtCFT will automatically recover the entire virtual cluster to the correct state within a few seconds and keep it running. Superior to all the existing fault tolerance mechanisms, VirtCFT provides a simpler and totally transparent fault tolerant platform that allows existing, unmodified software and operating system (version unawareness) to be protected from the failure of the physical machine on which it runs. We have implemented this system based on the Xen virtualization platform. Our experiments with real-world benchmarks demonstrate the effectiveness and correctness of VirtCFT.
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