[CentOS-virt] High CPU usage when running a CentOS guest inVirtualBox

Tue Sep 1 13:33:49 UTC 2009

Hi,

I just closed a service-request with sun.
Topic: Why is Win32 slower running with two CPUs under VBox 3 than
running with one CPU on VBox 2?

I am running VBox on CentOS 5 64 bit (AMD Athlon Dual Core).

The problem is - according to sun - the IO-APIC-emulation:
On 32-bit-systems this io-apic-emulation (needed for passing interrupts
between CPUs) has to use a full software-context-switching - making
things slow.

I tried recreating the problem with CentOS 5 64 Bit as VM, two CPUs: no
problem
With CentOS 5 32 Bit as VM: same problem.

I guess some problems with multi-cpu-VMs using 32-bit-operating-systems
on a 64-bit hardware are related to this - no matter if you are using
xen (fully virtualized), VirtualBox or VMWare.

Kind regards

Nils 

> -----Original Message-----
> From: centos-virt-bounces at centos.org 
> [mailto:centos-virt-bounces at centos.org] On Behalf Of Akemi Yagi
> Sent: Monday, July 06, 2009 10:24 PM
> To: Discussion about the virtualization on CentOS
> Subject: Re: [CentOS-virt] High CPU usage when running a 
> CentOS guest inVirtualBox
> 
> On Mon, Jul 6, 2009 at 10:22 AM, Sagi Bashari<sagi at boom.org.il> wrote:
> 
> > On my new box where I currently encounter the problem I tried 
> > installing the regular 2.6.18-92.1.22 kernel with the "divider=10 
> > clocksource=acpi_pm" parameters like you suggested, and 
> also the old 
> > kernel-vm package, and in both of these attempts idle host 
> CPU usage 
> > was at 50%. So it looks like although the symptoms are the same the 
> > cause is different.
> >
> > I guess it may be related to the newer version of VirtualHost, the 
> > different hardware or the different operating system. Any idea what 
> > else I can try to reduce the CPU usage on this host?
> 
> Because the issue is most likely related to VirtualBox and 
> Windows rather than CentOS, you may have a better chance of 
> getting help by going to the VB channels:
> 
> http://www.virtualbox.org/wiki/Community
> 
> Akemi
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