why poor network throughput with virtio on Kilo

asked 2015-06-16 17:26:30 -0600

anonymous user


updated 2015-06-16 17:35:33 -0600

Hi I just installed Kilo,

Running on RHEL 7 hypervisors, I ran up two VMs on different hosts with a 10G link between them. With SR-IOV I get great performance as expected. With standard virtio + vhost, the performance is very poor.

A iperf test, shows I can get line speed between 2 VMs (when using virtio)

iperf -c
Client connecting to, TCP port 5001
TCP window size: 22.5 KByte (default)
[  3] local port 57195 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  8.78 GBytes  7.54 Gbits/sec

But when running a load test for a http websever, at around 2000 http requests, the throughput appears to slow (latency increases) although packets aren't getting dropped on the VM interface. N.B that I don't see this issue with SR-IOV, which makes me thing the VM settings are fine, but it could be the virtio driver, hypervisor config (possible ovs) or host nic driver. The tap devices have a low txqueue length, but this is the same for the last release.

Is there any default throttling going on with the latest version of Kilo.

Can anyone recommend tunings for the hypervisor or virtio driver to improve the performance? In past versions of Openstack I've been able to hit around 5000 http requests per second.

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Could you please tell me how you are measuring the HTTP throughput?

uts9 gravatar imageuts9 ( 2015-06-17 01:49:59 -0600 )edit

Is there any default throttling going on with the latest version of Kilo.

Did you see packet drops on VM's tap interface? If you did not check it, can you log in to the host where VM is running and do "ifconfig tap-xyz" to see if packet drop counters increase?

Nodir gravatar imageNodir ( 2015-08-11 21:30:12 -0600 )edit

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answered 2016-09-12 12:50:46 -0600

ospz2014 gravatar image

you have any update on this ?

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Asked: 2015-06-16 17:26:30 -0600

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Last updated: Sep 12 '16