dividing host CPU performance

dividing host CPU performance

[Břeťa Vomočil]

Hi,
I want to divide host CPU performance between 2 VM in specified ratio. I use Cgroups system and cpu.shares files, but I'm not much successful in doing that.

My scenario:
- 2 VM - Ubuntu server 8.10 with 4 VCPU, QCOW2 disk and about 300MB memory running on host CPU with 4 cores
- in Cgroups: 
1st VM - cpuset.cpus = "0-3", cpuset.mems="0", cpu.shares="3072", tasks=<appropriate_VM_PID>
2nd VM - cpuset.cpus = "0-3", cpuset.mems="0", cpu.shares="1024", tasks=<appropriate_VM_PID>

Actual result:
Performance isn't divided 3:1 (in favor of the first VM) but 1:1.

I'm looking for an approach which gives me abilities like the Xen has with its scheduling parameters "cap" and "weight". I would appreciate any help how to solve this issue - I don't insist on Cgroups, but it seems like an capable solution, but for me it doesn't work (it is also possible, that my scenario miss some necessary setting).

Thanks in advance for any constructive advices
Breta

Re: dividing host CPU performance

[Břeťa Vomočil]

>If your hardware supports it you could look into:
>
>http://www.linuxmanpages.com/man8/numactl.8.php

Yes, my HW support it (I have already used it for keeping a VM on specified CPU core), but it doesn't solve the "generic ratio problem". For this case it can be usable - ratio 3:1 on 4-core CPU is simple task with numactl, I agree, but I'm looking for some more generic solution where you can make different ratios, which is not possible to do with numactl (for instance 4:1 on 4 cores).

Re: dividing host CPU performance

[Thomas Besser]

 Břeťa Vomočil wrote:
> I want to divide host CPU performance between 2 VM in specified ratio.

Perhaps 'cpulimit' (http://sourceforge.net/projects/cpulimit/) can do this!?

HTH
Thomas 

Re: dividing host CPU performance

[breta]

 Břeťa Vomočil napsal(a):
> Hi,
> I want to divide host CPU performance between 2 VM in specified ratio. I use Cgroups system and cpu.shares files, but I'm not much successful in doing that.
>
> My scenario:
> - 2 VM - Ubuntu server 8.10 with 4 VCPU, QCOW2 disk and about 300MB memory running on host CPU with 4 cores
> - in Cgroups: 
> 1st VM - cpuset.cpus = "0-3", cpuset.mems="0", cpu.shares="3072", tasks=<appropriate_VM_PID>
> 2nd VM - cpuset.cpus = "0-3", cpuset.mems="0", cpu.shares="1024", tasks=<appropriate_VM_PID>
>
> Actual result:
> Performance isn't divided 3:1 (in favor of the first VM) but 1:1.
>
> I'm looking for an approach which gives me abilities like the Xen has with its scheduling parameters "cap" and "weight". I would appreciate any help how to solve this issue - I don't insist on Cgroups, but it seems like an capable solution, but for me it doesn't work (it is also possible, that my scenario miss some necessary setting).
>
> Thanks in advance for any constructive advices
> Breta
>
>
>
>
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>   
Some time passed without any solution similar to the complex cgroups
(thanks for all replies)... could you please advise me, which mail
conference would be better to ask for that? It is very important for me
to solve this issue...

Thanks
b.