[one-users] the problem of the CPU in the virtual machine's template (Users Digest, Vol 59, Issue 76)

[Rolandas Naujikas]

On 2013-01-24 05:52, cmcc.dylan wrote:
> what's more, libvirt cann't see the CPU parameter! sou i think CPU is
> only used for overcommiting in opennebula level.

In Xen/KVM it is passed to Xen credit scheduler or KVM cgroup 
configuration for minimal CPU share. So if you put CPU=0.25,VCPU=1, then 
1 KVM thread will use 1 host CPU, until host becomes too busy, then it 
tries to schedule at least 0.25 of 1 host CPU (core) time.

Regards, Rolandas Naujikas

> At 2013-01-24 11:42:31,"cmcc.dylan" <dx10years at 126.com> wrote:
>
>
> if VCPU=4, i think the host will fork 4 process on behalf of this vm,
> because i see it is so implemented in the qemu code. I am very
> confused about this part of opennebula!
>
>
> At 2013-01-24 11:31:34,"Steven C Timm" <timm at fnal.gov> wrote:
>
>
> VCPU is the parameter that controls how many cores appear internally
> in the virtual machine.  I. e. if you have VCPU=4
>
> Your VM will have 4 cores, but there will still only be one kvm
> process as seen in the hypervisor that corresponds to it.
>
> In a typical KVM setup it is possible to allocate more VCPU per VM
> host than the VM host has real cores.
>
> I am not exactly sure what CPU does, but it does affect the FCPU and
> ACPU as seen in the onehost list output.
>
>
>
> Steve Timm
>
>
>
> From:users-bounces at lists.opennebula.org
> [mailto:users-bounces at lists.opennebula.org] On Behalf Of cmcc.dylan
> Sent: Wednesday, January 23, 2013 9:26 PM
> To:users at lists.opennebula.org Subject: [one-users] the problem of the
> CPU in the virtual machine's template
>
>
>
> Hi, everyone!
>
>
>
> I have a doubt what's the accurately means of CPU in the vm's
> template.
>
> For a example, if we define a vm which has CPU=1 and VCPU = 4. In
> this condition , what's result in the host os?
>
> Does the host os fork 4 process on behalf of this vm and does  the 4
> process get 4 cores if the host's scheduler allows that.
>
>
>
> I want to know the differences between "CPU=4,VCPU=4" and
> "CPU=1,VCPU=4".
>
>
>
>
>
>
>
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