Yes, indeed.... I've modified the number of cpus via the command line : VBoxManage modifyvm MyVM --cpus x From 3 cpus, the performances go down... But I don't really understand why... If someone can give me ways of explanations... Le 22/03/11 20:52, Kevin Martin a écrit : > > On 03/22/2011 01:00 PM, Christopher A. Williams wrote: >> 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) >> > But that's not what the OP said. He said that the machine had 24 cores and the the VM's were being allocated to only a cpu or two. > It sounds like the OP has multiple VM's with multi virtual cpu's per VM setup and that either the virtual machine manager on the > host wasn't allocating the virtual cpu's around correctly or that the kernel is not allocating them correctly. He doesn't mention > which version of VirtualBox (he's not using VMWare) he's using, nor does he mention if he's tried to allocate more virtual cpu's > than would fit on 2 physical cpu's. It's possible that he just doesn't have enough virtual cpu's allocated to need more than 2 > physical cpu's in use. > > K -- 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
