[ovirt-users] Ovirt VM Performance abd CPU times

[Xavier Naveira]

On 10/29/2014 03:07 PM, Xavier Naveira wrote:
> On 10/29/2014 01:26 PM, Daniel Helgenberger wrote:
>> On 29.10.2014 11:48, Xavier Naveira wrote:
>>> On 10/29/2014 11:47 AM, Xavier Naveira wrote:
>>>> On 10/29/2014 11:40 AM, Daniel Helgenberger wrote:
>>>>>
>>>>>
>>>>> On 29.10.2014 10:21, Xavier Naveira wrote:
>>>>>> Hi,
>>>>>>
>>>>>> We are migrating our ifrastructure from kvm+libvirt hypervisors to
>>>>>> ovirt.
>>>>>>
>>>>>> Everything is working fine but we're noticing that all the qemu-kvm
>>>>>> processes in the hypervisors take a lot of CPU.
>>>>> Without further details of the workload this is hard tell. One
>>>>> Reason I
>>>>> can think of might be KSM [1]. Is it enabled on your cluster(s)?
>>>>> What is
>>>>> your mem over-commitment setting?
>>>>>
>>>>> Note, IIRC the KSM policy is currently hard coded; it will start at
>>>>> 80%
>>>>> host mem usage.
>>>>>
>>>>> [1] http://www.ovirt.org/Sla/host-mom-policy
>>>>>>
>>>>>> The typical example is an idle machine, running top from the machine
>>>>>> itself it reports cpu use percentages below 10% and loads (with 2
>>>>>> processors) of 0.0x. The process running that machine in the
>>>>>> hypervisor
>>>>>> rports cpu uses in the order of the 80-100%.
>>>>>>
>>>>>> Should the values look like this? Why are the idle machines eating
>>>>>> up so
>>>>>> much CPU time?
>>>>>>
>>>>>> Thank you.
>>>>>> Xavier
>>>>>>
>>>>>> _______________________________________________
>>>>>> Users mailing list
>>>>>> Users at ovirt.org
>>>>>> http://lists.ovirt.org/mailman/listinfo/users
>>>>>>
>>>>>
>>>>
>>> Hi, thank you for the answer.
>>>
>>> I've been trying to work out some pattern and realized that the VMs
>>> using that much cpu all are Redhat 5.x, the Readhat 6.x doesn't exhibit
>>> this kind of high cpu use. (we run only redhat/centos 5.x/6.x on the
>>> cluster)
>> What OS are the hosts running? In case of EL6, make sure you have
>> tuned-0.2.19-13.el6.noarch installed [1].
>
> That's exactly the version we've in the hypervisors.

I checked the value of kernel.sched_migration_cost and it is already 
5000000, but it was a good shot :)

>
>>
>> To further investigate please post Engine, VDSM, libvirt and kernel
>> versions from the hosts.
>
> vdsm-xmlrpc-4.14.11.2-0.el6.noarch
> vdsm-cli-4.14.11.2-0.el6.noarch
> vdsm-python-4.14.11.2-0.el6.x86_64
> vdsm-4.14.11.2-0.el6.x86_64
> vdsm-python-zombiereaper-4.14.11.2-0.el6.noarch
>
> libvirt-client-0.10.2-29.el6_5.12.x86_64
> libvirt-0.10.2-29.el6_5.12.x86_64
> libvirt-lock-sanlock-0.10.2-29.el6_5.12.x86_64
> libvirt-python-0.10.2-29.el6_5.12.x86_64
>
> 2.6.32-431.23.3.el6.x86_64 #1 SMP Wed Jul 16 06:12:23 EDT 2014 x86_64
> x86_64 x86_64 GNU/Linux
>
>
>>
>> [1] https://access.redhat.com/solutions/358033
>>>
>>> I'll take a look to the KSM config.
>>>
>>> Cheers,
>>>
>>> Xavier
>>>
>>
>