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Instance has weaker internet speed than the host

asked 2018-11-11 05:43:05 -0500

mariusleu gravatar image

I am running an Openstack Rocky with openvswitch agent and vxlan tenant networks. VMs are created in a vxlan network and have associated public floating IPs.

For example, the following download test results in dramatic download speed difference:

wget -O /dev/null

VM - 5MB/s

Network node - 30MB/s

I've noticed if I run download tests from my city/country, the download speed in the VM increases (looks like as far the server is / as many hops are in between, the download speed in the VM decreases).

I've tried disabling the offloads using ethtool but no luck.

I can't find a reasonable explanation about this.

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answered 2018-11-12 04:48:33 -0500

game-on gravatar image

Have you tried running an iperf test from the host and comparing that to a test from the VM?

Check the MTU settings - you may need to reduce the MTU to 1450 or below on the VM.

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mtu is already at 1450 (lowered it to 1400 but no effect). iperf however does much better than wget, against the same server: VM - 120 Mbits/sec - 150 Mbits/sec; Host - 250+ Mbits/sec

mariusleu gravatar imagemariusleu ( 2018-11-12 08:03:54 -0500 )edit

One thing that is really strange to me, while performing the wget/iperf tests I am also doing tcpdump on the qr-* (qrouter) namespace. In the qrouter namespace of the network node I see the "seq" packets and on the qrouter of the compute I see the "ack" packets.

mariusleu gravatar imagemariusleu ( 2018-11-12 08:08:40 -0500 )edit

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Asked: 2018-11-11 05:43:05 -0500

Seen: 48 times

Last updated: Nov 12 '18