CPU performance related questions

[mot]

Sorry, questions not directly related to PVE. but I want to find out the answers.

1. As far as I know, it is possibly to assign 1 or more VCPU to VM using KVM.

But is it possible to control real CPU usage by every VM?
Can I config elsewhere that VM1 can consume no more than 10 % of real CPU time, and VM2 can consume no more than 20 % CPU time.

Also, what about privileges?
Can I config that VM1 has more privileges than VM2 and if real CPU is busy, VM1 will be first on queve?

The same question about openVZ, does version included in PVE 1.0 include CPU scheduler?

2. What about maxinum number of VM under KVM?

In order to get stable system, the max number of VM must be no more than the number of real CPU cores?
For example, If I have quad core xeon, it is better to start no more than 4 VMs on it?

 

[RenatoMN]

I was close to open a new thread, but I will post it here, since it is related.

I have a Core 2 Duo E6750 (2.66Ghz) and planning to have 2 or 3 VMs (with a "high" load like FreeNX remote access (1 or 2 users each VM only). What do you recommend, OpenVZ or KVM? I couldn't find your suggestions about when choose KVM and when choose OpenVZ.

If I go with OpenVZ, will all the processor power be used? Also, is there a way to "priviledge" a VM? - I think I'm doing the same question mot made above

Thanks in advance

 

[tom]

Sorry, questions not directly related to PVE. but I want to find out the answers.

1. As far as I know, it is possibly to assign 1 or more VCPU to VM using KVM.

yes, 16 cpus.

But is it possible to control real CPU usage by every VM?
Can I config elsewhere that VM1 can consume no more than 10 % of real CPU time, and VM2 can consume no more than 20 % CPU time.

Also, what about privileges?
Can I config that VM1 has more privileges than VM2 and if real CPU is busy, VM1 will be first on queve?

The same question about openVZ, does version included in PVE 1.0 include CPU scheduler?

see options, cpu units.

2. What about maxinum number of VM under KVM?

In order to get stable system, the max number of VM must be no more than the number of real CPU cores?
For example, If I have quad core xeon, it is better to start no more than 4 VMs on it?

just depends on the load/settings you put on the VM´s. By using OpenVZ containers you can get higher density.

 

[RenatoMN]

Sorry for posting again. But looks like tom was already typing the message above when I posted mine. Just bumping then he can read it.

Thanks

 

[tom]

I was close to open a new thread, but I will post it here, since it is related.

I have a Core 2 Duo E6750 (2.66Ghz) and planning to have 2 or 3 VMs (with a "high" load like FreeNX remote access (1 or 2 users each VM only). What do you recommend, OpenVZ or KVM? I couldn't find your suggestions about when choose KVM and when choose OpenVZ.

If I go with OpenVZ, will all the processor power be used? Also, is there a way to "priviledge" a VM? - I think I'm doing the same question mot made above

Thanks in advance

If you have Linux as guest, always go for OpenVZ, just a view facts:

• no virtualized hardware, therefore near native performance
• very fast to deploy, just about 5 seconds to start a new VM
• much smaller VM´s
• better management features
• stable technology (OpenVZ is the base of Virtuozzo, market leader in virtualization for hosting companies)

 

[RenatoMN]

Thanks for your reply.

However, I can't see any options regarding CPU resources on PVE 0.9beta2 (except the grayed out field "CPUs" filled with 1). -- OVH didn't sent us instructions on how to update to 1.0 yet

Is this disabled for >1 processors instability (like KVM), or does OpenVZ use all cores by default? I'm afraid this "1" limit the VM performance, because I'm creating just 1 VM for now, the other 1 or 2 will be sporadically created, and used for a short period, most part of the time, there will be only 1 VM, then I want it the more performance it can have.

Thanks in advance

 

[dietmar]

Openvz currently uses all available CPUs by default.

- Dietmar

 

[mot]

tom
CPU units are used in openVZ.

But what about KVM? I found no parametres like cpuunits in KVM.

 

[dietmar]

CPU units are used in openVZ.

But what about KVM? I found no parametres like cpuunits in KVM.

We also use CPU units for KVM.

- Dietmar

 

[jmjosebest]

In total, how many units have my cpu?

QuadCore 2Ghz

 

[dietmar]

In total, how many units have my cpu?

None. cpuunits is a relative value:

 --cpuunits num
           CPU weight for a container. Argument is positive  non-zero  number,
           passed  to  and  used  in the kernel fair scheduler. The larger the
           number is, the more CPU time this container gets. Maximum value  is
           500000,  minimal  is  8.   Number is relative to weights of all the
           other running containers.  If cpuunits are not  specified,  default
           value of 1000 is used.