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.
Gordon Messmer wrote:
On 06/02/2017 04:32 AM, hw wrote:
What may cause the high 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*"?
qemu-img-1.5.3-126.el7_3.6.x86_64 qemu-kvm-tools-1.5.3-126.el7_3.6.x86_64 qemu-kvm-common-1.5.3-126.el7_3.6.x86_64 qemu-kvm-1.5.3-126.el7_3.6.x86_64
The definitions aren�t too long, I could post them here. There�s nothing special about them AFAICT; I disabled USB and am trying to use kvmclock.
I�m finding the number of "Local timer interrupts" suspicious. From 'cat /proc/interrupts' for CPU0:
Tue Jun 6 20:01:53 CEST 2017: 217433736 Thu Jun 8 13:23:04 CEST 2017: 350172149
That seems an awful lot of interrupts. Is this normal?
There�s also a huge amount of "Rescheduling interrupts" (102113959 earlier, now 209740910). The VMs are pinned to CPUs, so what�s being rescheduled so frequently?
I can observe that CPU load of the host goes up with increases in network traffic of the guest. Is it a bad idea to assign a bonding interface to a bridge?
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hw