Application of full virtualization software KVM

Application of full virtualization software KVM

I. Introduction to KVM virtual machines

The short name of Kernel-based Virtual Machine is an open-source system virtualization module. It inherits from the main release version of Linux after Linux2.6.20. It uses the Linux Scheduler for management, so compared with Xen, its core source code is few. KVM has become one of the academic VMM.

Kvm is just a linux kernel module. After kvm is installed in linux, linux becomes a hypervisor, that is, VMM, for virtual management of CPU and memory, and qemu tool, this allows you to create and manage virtual machines and monitor various I/O devices. After purchasing kvm, RedHat provides a dedicated qemu-kvm management tool suitable for redhat systems.

Kvm can only run on CPUs that support hardware virtualization and only supports 64 bits. Kvm is a fully virtualized implementation software.

Ii. KVM Architecture

Above kvm Architecture

After kvm is installed, the kernel becomes very strange. The mode is divided into three parts: Kernel Mode, user mode, and guest mode.

VCPU: CPU implemented by thread Simulation

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RHEL6 KVM virtualization creates a bridge NIC-Bridge

RedHat Linux KVM Virtual Machine bridging

Installation/bridging settings of KVM in CentOS 5.6/virtual machine creation and operation

The/bin/qemu-KVM problem cannot be found when the kvm virtual machine is installed with libvirt In Ubuntu.

Install and configure the KVM Virtual Machine in RedHat6.5

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Two main components of KVM:

1./dev/kvm: Manages virtual machine device files. A user space program can call its ioctl () to create, start, and manage virtual machines. It is a character device; its main operations include:

Create a virtual machine;

Allocate memory for virtual machines;

Read and Write VCPU registers;

Inject interrupt requests to VCPU;

Run VCPU;

2. qemu process: components that work in the user space, used for I/0 type hardware devices of the Policy PC.

Iii. KVM Memory Management

KVM inherits many features of Memory Management in Linux. For example, the memory allocated to the virtual server can be exchanged to the swap space and large memory pages can be used to achieve better performance, the support for NUMA allows virtual machines to efficiently access larger memory space.

KVM Based on Intel's EPT (Extended Page Table) or AMD's RVI (Rapid Virtualization Indexing) technology can support updated memory virtual functions, which can reduce CPU usage, and improve the throughput.

In addition, KVM uses the Kernel feature KSM (Kernel Same-page Merging) to implement the Memory page. KSM scans the memory of each virtual machine to find the same memory page between the virtual machines, and merges the memory into a separate page shared by various related virtual machines. When a virtual machine tries to modify the data on this page, KSM will re-provide it with a new page copy. In practice, there is a high probability that the same memory page appears between virtual machines running on the same physical host with the same GuestOS, such as the shared library, the kernel or other memory objects may display the same memory page. Therefore, KSM technology can reduce memory usage and improve overall performance.

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