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Chapter 25. Virtualization

Performance monitoring in KVM guests
As a Technology Preview, KVM can virtualize a performance monitoring unit (vPMU) to allow virtual machines to use performance monitoring. Additionally it supports Intel's “architectural PMU” which can be live-migrated across different host CPU versions, using the -cpu host option.
The virtual performance monitoring feature allows virtual machine users to identify sources of performance problems in their guests, using their preferred pre-existing profiling tools that work on the host as well as the guest. Note that this is an addition to the existing ability to profile a KVM guest from the host.
System monitoring using SNMP
As a Technology Preview, Red Hat Enterprise Linux 6 allows Simple Network Management Protocol (SNMP) to be used for system monitoring. This allows KVM hosts to send SNMP traps on events so that hypervisor events can be communicated to the user via standard SNMP protocol. In addition, SNMP is capable of performing basic virtual networking operations, such as starting and stopping the virtual domain.
Zero-copy compatibility for macvtap-vhost
The macvtap-vhost zero-copy capability is available on Red Hat Enterprise Linux 6 as a Technology Preview. This feature allows running networking work loads in very high wire speeds but with low CPU resource consumption, and it does not limit other features such as memory overcommit and guest migration, which is not the case when using PCI device assignment to achieve the wire speed. Note that this feature is disabled by default.
vCPU hot unplug
Although hot-plugging a virtual CPU (vCPU) is a supported operation, hot-unplugging a vCPU remains a Technology Preview in Red Hat Enterprise Linux 6, and is strongly recommended not to be used in high-value deployments.