On Tue, 2011-03-22 at 12:25 -0500, Kevin Martin wrote: > > On 03/22/2011 12:11 PM, Patrick Bartek wrote: > > --- On Tue, 3/22/11, Luc MAIGNAN <luc.maignan@xxxxxxxxxxxx> wrote: > > > >> I use VirtualBox on a RHEL5 with 24 cores (6 x4-cores > >> processors). > >> But it seems like only one or two processors are used. How > >> can I > >> configure VirtualBox and/or my virtual machine to allow it > >> to use all > >> processors ? > > Does this not work: Start the VirtualBox interface, choose the virtual machine you want to work on, but don't start it; click on System in the Details list, choose Processor, set Processor(s) slider up to the number of virtual CPUs you want to use. > > > > >From the VirtualBox v. 3.1.6 manual: > > > > > > 3.4.2 “Processor†tab > > > > On the “Processor†tab, you can set how many virtual CPU cores the guest operating systems should see. Starting with version 3.0, VirtualBox supports symmetrical multi-processing (SMP) and can present up to 32 virtual CPU cores to each virtual machine. > > You should not, however, configure virtual machines to use more CPU cores than you have available physically. > > > > > > > > B > > It sounds as if the host is not allocating VM's to more than a few CPU's. Adding additional CPU's in the VB screen may or may not > cause the host O.S. to work as planned. It may just allocate more VM virtual CPU's to the same physical CPU's. I'm thinking that > there's a bug in the host O.S. kernel that's not allocating the VM's to all of the CPU's correctly. So "taskset" may be the only > answer until he can get on a newer kernel. ...Ummm no, that's not how this works. In reality, allocating more virtual CPUs (aka a vCPU or virtual processor) to a VM - be it VirtualBox, VMware, Hyper-V, etc., actually does a have a direct correlation to the number of CPU cores that are used by that VM on the physical host. The more vCPUs, the more physical cores are allocated to the VM by the system scheduler foa given set of CPU cycles (be that the hypervisor, the host OS, or both as appropriate). That's also why you shouldn't (actually can't) allocate more vCPUs than the lesser of either the number of CPU cores on the host system or the total number that the hypervisor will support (32 in the case of vBox). Be careful when doing multi-vCPU VMs though. Adding more does not necessarily mean you will get a boost in performance of either the VM or the host system. In fact, there are cases where this can actually cause a performance decrease. Make sure you know that the VM will use the number of cores (vCPUs) you are wanting to allocate. This is also something that must be pre-allocated in vBox. Thus, the correct procedure is to add virtual CPUs via the "Processor" tab as described above. Other hypervisors (VMware vSphere, Hyper-V) are starting to support "hot add" of vCPUs on Windows and Linux VMs. None, however, support a "hot remove" of vCPUs at this time. Cheers, Chris (VMware Certified Advanced Professional - Datacenter Design) -- ====================== "If we don't succeed, we run the risk of failure." -- Former President Bill Clinton -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
