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

[cmcc.dylan]

Thank you.

Do you mean that if the host isn't busy and VCPU=4, CPU=1 and CPU=2 have the equal effect.
So CPU has effects only when the host os is overcommited.







At 2013-01-24 14:28:32,"Rolandas Naujikas" <rolandas.naujikas at mif.vu.lt> wrote:
>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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