Hi,
we were investigating some performance issue that an application on our
kvm VMs had and noticed that network latency is much worse in a VM
compared to actual hardware.
Initially we were using virtio network cards, but not vhost-net. After
enabling vhost the performance improved quite a bit, but is still only
at around 50% of what the actual hardware can do.
The question is, what can we expect? CPU utilization was never higher
than 50% kvm and 20% vhost. Other details are below, please let me know
if you can recommend other tests or important details that I could
provide.
I ran the following tests using netperf -t UDP_RR (all results are
transactions/sec):
* host->host 19k
* vm->its host 17k
* vm->vm (same host) 22k
* vm->vm (diff. hosts) 7k
Host: Debian squeeze using a 3.5.2 kernel
KVM: 1.1.2 (bpo)
Host CPU: Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60GHz
VM: Debian squeeze using a 3.2.20 kernel
Network: e1000 & gigabit switch
Command-line:
-cpu host -name testvm -m 12288 -smp 16 -pidfile
/var/run/ganeti/kvm-hypervisor/pid/testvm -balloon virtio -daemonize
-monitor
unix:/var/run/ganeti/kvm-hypervisor/ctrl/testvm.monitor,server,nowait
-serial
unix:/var/run/ganeti/kvm-hypervisor/ctrl/testvm.serial,server,nowait
-usbdevice tablet -vnc 127.0.0.1:5102 -netdev
type=tap,id=netdev0,fd=8,vhost=on -device
virtio-net-pci,mac=52:54:00:00:01:e6,netdev=netdev0 -netdev
type=tap,id=netdev1,fd=9,vhost=on -device
virtio-net-pci,mac=52:54:00:00:01:e7,netdev=netdev1 -qmp
unix:/var/run/ganeti/kvm-hypervisor/ctrl/testvm.qmp,server,nowait -S
Thanks,
~David
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