[OmniOS-discuss] kvm io 10 times slower after r151010 -> r151012 upgrade

[Tobias Oetiker]

So tonight, we finally took the plunge and upgraded our zfs/kvm
server to r151012 ... the results were terrible. The kvm booted
very slowly and all networking felt really slow ... so I did a
little test:

  ubutu-14.04-guest$ dd if=/dev/zero bs=1M count=20 | ssh omnios-r151012-host dd of=/dev/null
  20971520 bytes (21 MB) copied, 6.27333 s, 3.3 MB/s

  ubutu-14.04-guest$ ssh omnios-r151012-host dd if=/dev/zero bs=1M count=20 | dd of=/dev/null
  20971520 bytes transferred in 8.010208 secs (2618099 bytes/sec)

These numbers were obtained using virtio net drivers but switching
to e1000 did not significantly change things.

So we booted back into r151010 again ... the difference was
immediately apparent ... but there are also number to back this up.

  ubutu-14.04-guest$ dd if=/dev/zero bs=1M count=20 | ssh omnios-r151010-host dd of=/dev/null
  20971520 bytes (21 MB) copied, 0.812479 s, 25.8 MB/s

  ubutu-14.04-guest$ ssh omnios-r151010-host dd if=/dev/zero bs=1M count=20 | dd of=/dev/null
  20971520 bytes (21 MB) copied, 0.545423 s, 38.5 MB/s

as you can see the difference in guest network performance is
roughly one magnitude ...

I have not tested disk performance explicitly, but even booting a
windows host took ages ... so I suspect whatever is causing this
influences all kvm guest IO.

cheers
tobi

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902