Hi Akemi,
KVM uses a para-virtualized approach?
With para-virtualized guests or with 32-bit guests running a single CPU there is no need to simulate the IO-APIC.
Kind regards
Nils
-----Original Message----- From: centos-virt-bounces@centos.org [mailto:centos-virt-bounces@centos.org] On Behalf Of Akemi Yagi Sent: Tuesday, September 01, 2009 6:15 PM To: Discussion about the virtualization on CentOS Subject: Re: [CentOS-virt] High CPU usage when running a CentOS guestinVirtualBox
On Tue, Sep 1, 2009 at 5:33 AM, Hildebrand, Nils, 232Nils.Hildebrand@bamf.bund.de wrote:
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.
Interesting. I do not have any 32-bit multi-cpu VMs myself, but I do have access to such guests running on a host (64-bit) using kvm. Both CentOS-5 32-bit VM and CentOS-4 32-bit VM show normal load (near 100% idle on all cpus). They have the divider=10 option by the way.
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