[CentOS-virt] High CPU usage when running a CentOSguestinVirtualBox

Hildebrand, Nils, 232 Nils.Hildebrand at bamf.bund.de
Mon Nov 9 11:47:08 UTC 2009


this weekend I took a closer look at KVM. I think that the paravirtualized XEN or Hyper-V-Approach is superior to the full virtualization.
Red Hat 6 will have XEN-Support (propably XEN 3.4 with power-consumption savings).

The only drawback is that you need modified Kernels for paravirtualization to work. Fully virtualized systems might be simpler if you have a very mixed environment without dedicated Administrators for every operating system.

Kind regards


> -----Original Message-----
> From: centos-virt-bounces at centos.org 
> [mailto:centos-virt-bounces at centos.org] On Behalf Of Filipe 
> Brandenburger
> Sent: Monday, September 14, 2009 9:24 PM
> To: Discussion about the virtualization on CentOS
> Subject: Re: [CentOS-virt] High CPU usage when running a 
> CentOSguestinVirtualBox
> Hi,
> On Mon, Sep 14, 2009 at 11:18, Dennis J. 
> <dennisml at conversis.de> wrote:
> > On 09/14/2009 04:53 PM, Akemi Yagi wrote:
> >> On Mon, Sep 14, 2009 at 7:24 AM, Hildebrand, Nils, 232 
> <Nils.Hildebrand at bamf.bund.de>  wrote:
> >>> KVM uses a para-virtualized approach?
> >>
> >> Not at this moment according to this Red Hat virtualization guide:
> >
> > Ugh, I guess that means my plans to switch from Xen to KVM have to 
> > wait until RHEL 6 is released.
> I don't believe KVM will *ever* support para-virtualization 
> in the same sense that Xen does.
> For instance, see this FAQ in KVM's website:
> http://www.linux-kvm.org/page/FAQ#What_is_the_difference_betwe
> en_KVM_and_Xen.3F
> I believe the point is that current support for VT in recent 
> processors is good enough to be able to run VMs with a native 
> kernel at the same speed that could only be achieved with a 
> para-virtualized kernel before. Therefore, the 
> para-virtualized approach is being discontinued as "a hack" 
> and the tendency is to improve VM technologies to run native 
> code only.
> On the other hand, there is now talk about para-virtualized 
> device drivers, which mean drivers that are optimized to run 
> in a VM environment, which I believe are important in getting 
> good performance from native kernels in VMs. The same concept 
> exists in Xen, when you run Windows in Xen you do it using 
> HVM (non-para-virtualized) mode, in which case you will only 
> get good performance by loading the Xen drivers on the 
> Windows machine, I believe the concept is the same there.
> HTH,
> Filipe
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