[Bug 1325560] Re: kvm virtio netdevs lose network connectivity under "enough" load

[Matt]

I am seeing a similar issue but instead of the network breaking I get
very variable latency. It's like the VM is pausing.

This only happens with virtio networking. Switching to e1000 fixes the
issue.

Ubuntu 14.04 3.13.0-30-generic on both the host machines and VM's with
bridge networking.


64 bytes from 10.3.0.2: icmp_seq=59 ttl=64 time=0.717 ms
64 bytes from 10.3.0.2: icmp_seq=60 ttl=64 time=0.706 ms
64 bytes from 10.3.0.2: icmp_seq=61 ttl=64 time=0.454 ms
64 bytes from 10.3.0.2: icmp_seq=62 ttl=64 time=0.635 ms
64 bytes from 10.3.0.2: icmp_seq=63 ttl=64 time=0.707 ms
64 bytes from 10.3.0.2: icmp_seq=64 ttl=64 time=2333 ms         # Starts here
64 bytes from 10.3.0.2: icmp_seq=65 ttl=64 time=856 ms
64 bytes from 10.3.0.2: icmp_seq=66 ttl=64 time=350 ms
64 bytes from 10.3.0.2: icmp_seq=67 ttl=64 time=80.1 ms
64 bytes from 10.3.0.2: icmp_seq=68 ttl=64 time=12.5 ms
64 bytes from 10.3.0.2: icmp_seq=69 ttl=64 time=2.71 ms
64 bytes from 10.3.0.2: icmp_seq=70 ttl=64 time=1.71 ms
64 bytes from 10.3.0.2: icmp_seq=71 ttl=64 time=0.597 ms
64 bytes from 10.3.0.2: icmp_seq=72 ttl=64 time=0.729 ms
64 bytes from 10.3.0.2: icmp_seq=73 ttl=64 time=0.727 ms
64 bytes from 10.3.0.2: icmp_seq=74 ttl=64 time=0.642 ms
64 bytes from 10.3.0.2: icmp_seq=75 ttl=64 time=0.715 ms
64 bytes from 10.3.0.2: icmp_seq=76 ttl=64 time=0.715 ms
64 bytes from 10.3.0.2: icmp_seq=77 ttl=64 time=0.776 ms
64 bytes from 10.3.0.2: icmp_seq=78 ttl=64 time=0.742 ms
64 bytes from 10.3.0.2: icmp_seq=79 ttl=64 time=0.770 ms

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Title:
  kvm virtio netdevs lose network connectivity under "enough" load

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