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 at centos.org > [mailto:centos-virt-bounces at 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, > 232<Nils.Hildebrand at 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. > > Akemi > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > http://lists.centos.org/mailman/listinfo/centos-virt >