[ovs-discuss] Open vSwitch performance with UDP traffic

[Ben Pfaff]

Please don't drop the mailing list.

I'd expect a dramatic drop in CPU consumption in that case.  There are
a few special cases where the upgrade wouldn't help.  One is if
in-band control is in use, another is if NetFlow is turned on, a third
is if LACP bonds with L4 port based hashing are turned on, and there
are probably a few others that don't come to mind immediately.

Version 2.0 helped with this more, too.

On Tue, Jan 21, 2014 at 11:14:03PM +0000, McGarvey, Kevin wrote:
> Sorry, I left out details in order to get an answer about whether kernel
> forwarding of single packet flows like this is even possible.
> 
> I was initially using the version that ships with RHEL 6.4, but I upgraded
> to openvswitch-1.11.0_8ce28d-1.el6ost.x86_64 and upgraded the kernel to
> 2.6.32-358.123.4.openstack.el6.x86_64.  I upgraded the kernel first, at
> the recommendation of one of our engineers who has been working a lot with
> OpenStack.  When that didn't reduce the CPU consumption I upgraded Open
> vSwitch.   But I didn't notice a drop in CPU consumption.
> 
> Some additional details:
> 
> The server is a Dell 710
> The NICs are Broadcom bcm5709
> We have 2 bridges configured, one for each NIC
> We are using VLANs
> 
> Kevin
> 
> On 1/21/14 5:55 PM, "Ben Pfaff" <blp at nicira.com> wrote:
> 
> >On Tue, Jan 21, 2014 at 10:50:30PM +0000, McGarvey, Kevin wrote:
> >> I am sending UDP DNS queries to a KVM guest through Open vSwitch
> >> running on the RHEL hypervisor.  With traffic of only 5K
> >> request/response pairs per second the CPU consumption of the
> >> ovs-vswitchd process is over 60%. The source IP and port change with
> >> each request, simulating normal UDP DNS traffic.  It appears that
> >> each request is being handled as a new flow and is being sent to the
> >> userspace process.  When I dump data flows with ovs-dpctl, there are
> >> thousands of flows that are never used.
> >> 
> >> Is there a way to get reasonable performance from Open vSwitch with
> >> this type of traffic?  I tried adding a flow with ovs-ofctl,
> >> specifying the destination MAC of the guest and everything else
> >> wildcarded, but I saw no change in the CPU consumption of
> >> ovs-vswitchd.
> >
> >You didn't say what version of OVS you're using.  The CPU% used for
> >this kind of traffic should drop dramatically with an upgrade to 1.11
> >or later.
>