On 10/29/2014 11:47 AM, Xavier Naveira wrote:

On 10/29/2014 11:40 AM, Daniel Helgenberger wrote:

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On 29.10.2014 10:21, Xavier Naveira wrote:

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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

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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

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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) I'll take a look to the KSM config. Cheers, Xavier