[CentOS-virt] XEN and RH 6

Scott McClanahan smcclanahan at sigovs.com
Tue Nov 10 18:52:36 UTC 2009

> Yeah.. Xen paravirtualized mmu is fast, and in some (many) cases beats
> CPU hardware virtualized mmu.
> KVM has 'pvmmu' aswell, but it's not as good, so KVM is faster with CPU
> hardware virtualization. But that's a problem of KVM only, they haven't
> managed to optimize the pvmmu. And they're going to drop it altogether.
> KVM people tend to say 'paravirtualized mmu is slow', but they just mean
> KVM implementation of it sucks :)
> -- Pasi

I haven't tested or seen any benchmarks but I wonder how much the
addition of a page table for virtualized guests will help.  Not to
mention newer features like a virtualized task priority register and
ASID could continue to require less paravirt code in the guest.  I get
my two new 5500 series servers in a few weeks so I'm pretty excited to
see some of the second gen hardware virtualization assist features in

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