Early testing has shown that Ubuntu, when run as a virtual guest taking advantage of the new paravirt-ops paravirtualization interface, delivers as promised: it runs faster and more efficiently that it would as an unmodified guest
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Paravirt_ops is an open interface that was developed by members of the Linux kernel community, including commercial vendors Red Hat, VMware, IBM and XenSource. It is designed to improve Linux virtualization performance by allowing the kernel to directly communicate with the hypervisor. It is based on the VMware's Virtual Machine Interface (VMI) proposed standard, and has been included in the mainline Linux kernel.