On Sat, 2020-10-10 at 18:25 -0400, Mark Wittling wrote:

Looking for someone who knows OpenStack with OpenVSwitch, and in addition to that, DPDK with OpenStack and OVS.I am using OpenStack Queens, with OpenVSwitch. The architecture I am using is documented here: https://docs.openstack.org/neutron/queens/admin/deploy-ovs-provider.htmlThe OVS I am using on the Compute Node, is compiled with DPDK, and I have enabled the datapath to netdev (DPDK) on br-prv (provider network bridge), and br-tun (tunneling bridge). But these two bridges, br-tun and br- prv, are patched into another OpenStack bridge, called br-int. I wasn’t actually sure about whether to tinker with this bridge, and wondered what datapath it was using.Then, I realized there is a parameter in the openvswitch_agent.ini file, which I will list here:

# OVS datapath to use. 'system' is the default value and corresponds to the # kernel datapath. To enable the userspace datapath set this value to 'netdev'. # (string value) # Possible values: # system - <No description provided> # netdev - <No description provided> #datapath_type = system datapath_type = netdev

So in tinkering with this, what I realized, is that when you set this datapath_type to system or netdev, it will adjust the br-int bridge to that datapath type.So here is my question. How can I launch a non-DPDK VM, if all of the bridges are using the netdev datapath type?

Here is another question. What if one of the flavors don’t have the largepages property set on them?

you cant we intentionally do not support miking the kernel datapath and dpdk datapath on the same host. incidentally patch port only function between bridge of the same data path type. so the br-int, br-tun and br-prv shoudl all be set to netdev. also if you wnat dpdk to process your tunnel trafic you need to assign the tunnel local endpoint ip to the br-prv assuming that is where the dpdk physical interface is. if you do not do this tunnel traffic e.g. vxlan will be processed by the ovs main thread without any dpdk or kernel acceleration. they will not get network connectivity. vhost-user requires mmapped=shared memory with an open file decriptor that is pre mapped and contiguious. in nova you can only get this one of two ways. 1 use hugpages or 2 use file backed memory. the second approch while it shoudl work has never acutlly been tested in nova with ovs-dpdk but it was added to libvirt for ovs-dpdk without hugepages and was added to nova for security tools that scan vm memory externally looking for active viruses and other threats.

I assumed OpenStack would revert to a system datapath and not use DPDK for those VM interfaces. no that would break the operation of all patch ports so it cant.

Well, I found out in testing, that is not the case. If you set all your bridges up for netdev, and you don’t set the property on the Flavor of the VM (largepages), the VM will launch, but it simply won’t work.

yes without file backed memroy that is created as i said above dpdk will not be able to map the virtio rings form the guest into its process space to tx/rx packets.

Is there no way, on a specific Compute Host, to support both DPDK (netdev datapaths) and non-DPDK (system datapaths)?Either on a VM interface level (VM has one interface that is netdev DPDK and another that is system datapath non-DPDK)?

correct there is no way to support both on the same host with openstack.until relitivly recently it was not supported by the ovs comunity either. i could be configured but it was not tested, supported or recommented by the ovs comunity and its is not supported with openstack.

Or on a VM by VM basis (VM 1 has 1 or more netdev datapath interfaces and VM 2 has 1 or more system datapath interfaces)?Am I right here? Once you set up a Compute Host for DPDK, it’s DPDK or nothing on that Compute Host? (edited) yes you can mix in the same cloud just on on the same host. for example if you are not using dvr we generally recommend dpdk on only the compute host and using kernel ovs on the contoller/networking nodes where the l3 agents are running.