Kvm/qemu And CPU Load

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Hi,

I have a server using its 4 physical network interfaces bonded, with the bonding interface added to a bridge. The bridge has the IP, and three VMs are using the bridge. Two of the VMs are running Debian, one is running Windoze 7.

CPU load caused by the qemu-kvm processes is way higher than I´m happy with. One of the Debian machine causes around
22% while it´s basically idle, the other one is around 3%, and the Windoze one is around 50. They are all mostly idle.

I can observe that when some network traffic is going on with the Windoze machine, it causes a CPU load of 200%. “Some network traffic” means that virt-top is showing 1M/2M RX/TX. Considering that the bonding interface is theoretically capable of handling
4Gbit full duplex, the 3Mbit are neglectable. Virtio drivers are being used.

Currently, virt-top shows 1.9% CPU for the Windoze machine and top shows 22% CPU load for the corresponding qemu-kvm process. There is almost not network traffic. The VM has 4 CPUs assigned.

What may cause the high CPU load? Something must be seriously wrong for an idle machine causing 22% CPU load and for the same machine, still basically idle, with a some network traffic to cause 200% CPU load on a Xeon 5690.

One thought on - Kvm/qemu And CPU Load

  • Offhand, it’s hard to say. I don’t see similar behavior. Can you post the libvirt XML definitions for those VMs somewhere? pastebin maybe?
    What’s the output of “rpm -qa qemu\*”?

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