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