Re: [Qemu-discuss] Any one have successfully make window 7 guest in kvm use more than 2 cpus/cores?

[Jakob Bohm]

On 7/24/2014 4:24 AM, Tony Su wrote:
>    Aside from verifying/supporting the previous posts which state that a
> Desktop OS like Win7 only supports 2 CPUs, I wonder why the effort to
> even deploy on multiple CPU. Today's OS (all I know of) fully take
> advantage of all physical CPUs no matter how many (or few) virtual
> CPUs are configured. The only reason I can conceive  of to configure
> multiple CPUs is to attempt to partition running processes on physical
> CPUs (not virtual) which I highly doubt would be an objective running
> any app on Win7 (or similar desktop).

The point isn't to partition.  It is to make the guest OS take advantage
of more CPUs, thus running faster.  The fact that different guest OS-es
have different topology restrictions causes frequent problems
configuring the virtual topology presented to them by virtual machines
such as qemu-tc, qemu-xen, qemu-kvm, VirtualBox, VMware and HyperV.

> On Wed, Jul 23, 2014 at 7:23 PM, Tony Su <address@hidden> wrote:
> >   
> > http://social.technet.microsoft.com/Forums/windows/en-US/970c999c-8ffc-4611-968c-7d0ceffbedd4/max-number-of-cpu-cores-that-windows-7-64-bit-will-recognize?forum=w7itprohardware
> >
> > Depending on your version of Windows 7, your license supports either
> > one or two CPU and any number of cores.
> >
> > Tony
> >
> > On Wed, Jul 23, 2014 at 6:45 PM, Scott Zhang <address@hidden> wrote:
> > > that is interesting. i use my opensuse 13.1 with i7 4cores.cpu and run win7
> > > as guest. win7 show 4 cpus correctly. guess the problem with fedora kvm or
> > > the xeon cpu. will try later to confirm
> > >
> > > On Jul 24, 2014 12:35 AM, "Jakob Bohm" <address@hidden> wrote:
> > > > On 7/23/2014 6:22 PM, Sai Prajeeth wrote:
> > > > > Try setting sockets=6,cores=1? I had this issue when running Solaris as
> > > > > guest. For some reason Solaris never detected any of the cores. It could
> > > > > only detect the sockets.
> > > > Unlikely to work.  Windows 7 (unlike the more expensive server licenses
> > > > for the same kernel) enforces a license restriction of max 2 physical
> > > > CPUs, each with unlimited cores (subject to the kernel design maximum
> > > > of at least 32).
> > > >
> > > > But try looking at the command line of the running qemu process.  Does
> > > > it actually specify 2 sockets with 4 cores each, or were the settings
> > > > somehow mistranslated from libvirt XML to qemu command line?
> > > >
> > > > Also, if you are using a computer with more than 2 physical sockets,
> > > > you may want to check if kvm passes through the physical or the command
> > > > line CPU topology to the guest.
> > > >
> > > > > On Wed, Jul 23, 2014 at 9:38 PM, Scott Zhang <address@hidden
> > > > > <mailto:address@hidden>> wrote:
> > > > >
> > > > >      __
> > > > >      __
> > > > >      Dear all:
> > > > >          I have been trying this for whole afternoon and whole night. I
> > > > >      have installed windows 7 as guest in kvm using virt-manager which
> > > > >      use qemu. And after I alloc it 6 vcpus, I noticed win7 only see 2
> > > > >      cpus in task manager. But in device manager, it shows 6 cpus. After
> > > > >      google a lot, looks many people say they workaround this by setting
> > > > >      the topology of CPU, which is technical correct.
> > > > >          But when I try to set sockets=2,cores=4 and several vairable
> > > > >      pairs. None is working. Win7 only see 2 at most. I am using fedora
> > > > >      20 with kernel 3.15 and the default qemu.
> > > > >          Can any one help?
> > > > >      Thanks
> > > > >      Regards
> > > > >      2014-07-24


Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  http://www.wisemo.com
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