Hello, I’m using 2 Ubuntu Xenial 16.04 LTS with the following: - kernel: 4.4.0-28-generic - OVS version: 2.5.0 (installed from ubuntu packages: openvswitch-common & openvswitch-switch)
I’m configuring a GRE tunnel between OVS bridges running on each of the machines with: ovs-vsctl add-port br0 tun0 -- set Interface tun0 type=gre options:remote_ip=x.x.x.x and I achieve connectivity between VMs, as desired, via the GRE tunnel. Problem: iperf test show really low performance (734 bits/sec !!) considering a baseline that shows almost 1G over the direct link. Troubleshooting performed: 1. increased MTU of the physical link on both sides: `ip link set dev enp0s8 mtu 2000` => same poor perf 2. increased MTU of the br0 on both OVS bridges: `ip link set dev br0 mtu 1700` => same poor perf [FYI: I performed the same operations on an older version of Ubuntu = Trusty 14.04 LTS, kernel 3.13.0-86, and after adjusting the MTU as above, the GRE performance was satisfactory ~ 414 Mbps !! ] I continued troubleshooting my Ubuntu Xenial 16.04 (kernel 4.4.0-28): 3. I noticed that this system has these interfaces gre0@NONE, gretap0@NONE, gre_sys@NONE (which did not appear on Ubuntu Trusty 14.04, kernel 3.13.0-86) and realized that Ubuntu Xenial 16.04 uses the linux kernel module ip_gre instead of the one provided by Open vSwitch: SNAPSHOT from Ubuntu Xenial 16.04 (kernel 4.4.0-28): ``` root@xenial ~$ lsmod | grep gre vport_gre 16384 1 ip_gre 20480 1 vport_gre ip_tunnel 28672 1 ip_gre gre 16384 1 ip_gre openvswitch 98304 3 vport_gre root@xenial ~$ dmesg | grep gre .. [ 379.947836] gre: GRE over IPv4 demultiplexor driver [ 379.955295] ip_gre: GRE over IPv4 tunneling driver [ 379.960352] device gre_sys entered promiscuous mode ``` SNAPSHOT from Ubuntu Trusty (kernel 3.13.0-86): ``` root@trusty ~$ lsmod | grep gre gre 13796 1 openvswitch root@trusty ~$ dmesg | grep gre [ 9.270743] gre: GRE over IPv4 demultiplexor driver root@box-0 ~$ ``` 3. It seems that latest OVS version uses vport_gre kernel module for GRE and this one depends on Linux GRE module (ip_gre): ``` root@xenial ~$ modinfo vport_gre filename: /lib/modules/4.4.0-28-generic/kernel/net/openvswitch/vport-gre.ko alias: vport-type-3 license: GPL description: OVS: GRE switching port srcversion: A4455AB407AE7569E81E791 depends: openvswitch,ip_gre intree: Y vermagic: 4.4.0-28-generic SMP mod_unload modversions ``` Questions: 1. is this intended - that the latest versions of OVS uses the linux GRE module (instead of its own, as it seem it was the case in the past)? 2. I tried stopping OVS and unloading the Linux GRE module - but that was unsuccessful. How should I fix my problem in order to achieve satisfactory level of performance over GRE ? Thank you, DC _______________________________________________ discuss mailing list discuss@openvswitch.org http://openvswitch.org/mailman/listinfo/discuss
