[ovs-discuss] High CPU usage due to L3/4 flows

Brad Hedlund brad.hedlund at gmail.com
Fri Dec 7 22:33:34 UTC 2012

Hi Bernhard,

Out of curiosity, have you tried using the *ovs-controller*?



On Wed, Dec 5, 2012 at 5:22 PM, Bernhard Schmidt <berni at birkenwald.de>wrote:

> Hi,
> I think this is a FAQ, but I seem to be blind enough to miss any clue
> about this issue.
> I have recently (test-)migrated our KVM-based virtualisation
> infrastructure from one-standard-bridge-per-VLAN to a fully VLAN-aware
> openvswitch (Debian testing, which means kernel 3.2.32 with
> openvswitch-datapath-dkms 1.4.2) because it feels much more natural to
> use.
> I don't think the actual configuration matters a lot, but here it comes
> - two GigE ports in active-standby bond0 to upstream switches
> - two GigE ports in LACP bond1 to partner
> I have ruled out any CPU load issues mentioned in the FAQ like loops and
> broadcast storms.
> My problem is that when I move some high traffic VMs to this host the
> CPU usage of ovs-vswitchd is massively increased. I'm reasonably sure
> this is due to the fact that there seems to be a flow setup for each L4
> connection through that vswitch, which in this case is highly
> unfortunate (firewall VM with a lot of concurrent sessions).
> root at virt1:~# ovs-dpctl show
> system at br0:
>         lookups: hit:5200011861 missed:829071115 lost:279074
>         flows: 34392
> I have already set other_config:flow-eviction-threshold=100000,
> otherwise it would be a lot worse. But I still have a CPU load that is
> several times higher than it was before with the standard bridge, and I
> still see occasional loss during high traffic periods.
> I don't actually need all that fancy OpenFlow stuff, so in my case a
> traditional switching based on MAC learning and the destination MAC
> would suffice. I cannot find any information whether that is possible.
> Thanks,
> Bernhard
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