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I have read that in para virtualization hosted virtual machines are aware that they are being virtualized, and this allows them to increase their performance. But, how does the hosted machine know they are virtualized as since we are not modifying any kernel parameters of the guest os while installing?

What do we need to do on the host OS to give it a performance increases resulting from recognising that it is in a virtual environment? What are the best ways to optimize a Ubuntu VM for in an xen environment?

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closed as not constructive by adaptr, Kenny Rasschaert, Shane Madden, Brent Pabst, Magellan Nov 11 '12 at 5:17

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up vote 5 down vote accepted

Paravirtualized Xen VMs used to use special paravirtualized (domU) kernels but modern kernels include domU features by default. That said, the kernel is able to detect when it is being run in Xen environment and use the domU interfaces then.

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