On 19.11.2019 20:45, William Tu wrote: > On Tue, Nov 19, 2019 at 05:52:22PM +0100, Ilya Maximets wrote: >> On 19.11.2019 17:16, Eelco Chaudron wrote: >>> >>> >>> On 7 Nov 2019, at 12:36, Ilya Maximets wrote: >>> >>>> Until now there was only two options for XDP mode in OVS: SKB or DRV. >>>> i.e. 'generic XDP' or 'native XDP with zero-copy enabled'. >>>> >>>> Devices like 'veth' interfaces in Linux supports native XDP, but >>>> doesn't support zero-copy mode. This case can not be covered by >>>> existing API and we have to use slower generic XDP for such devices. >>>> There are few more issues, e.g. TCP is not supported in generic XDP >>>> mode for veth interfaces due to kernel limitations, however it is >>>> supported in native mode. >>>> >>>> This change introduces ability to use native XDP without zero-copy >>>> along with best-effort configuration option that enabled by default. >>>> In best-effort case OVS will sequentially try different modes starting >>>> from the fastest one and will choose the first acceptable for current >>>> interface. This will guarantee the best possible performance. >>>> >>>> If user will want to choose specific mode, it's still possible by >>>> setting the 'options:xdp-mode'. >>>> >>>> This change additionally changes the API by renaming the configuration >>>> knob from 'xdpmode' to 'xdp-mode' and also renaming the modes >>>> themselves to be more user-friendly. >>>> >>>> The full list of currently supported modes: >>>> * native-with-zerocopy - former DRV >>>> * native - new one, DRV without zero-copy >>>> * generic - former SKB >>>> * best-effort - new one, chooses the best available from >>>> 3 above modes >>>> >>>> Since 'best-effort' is a default mode, users will not need to >>>> explicitely set 'xdp-mode' in most cases. >>>> >>>> TCP related tests enabled back in system afxdp testsuite, because >>>> 'best-effort' will choose 'native' mode for veth interfaces >>>> and this mode has no issues with TCP. >>> Patch in general looks good, two small comments inline. >> >> Thanks for review. >> >>> >>> The only thing that bothers me is the worse performance of the TAP >>> interface with the new default config. Can we somehow keep the old behavior >>> for TAP interfaces? >> >> Could you check if TCP works over tap interfaces in generic mode? >> For me the point is that correctness is better than performance. >> I also hope that native implementation for tap will be improved >> over time. >> > > I agree that we should first make sure correctness. > I created a simple TCP test using br0, since br0 is a tap device. > Unfortunately it does not work... > > --- > ovs-vsctl -- add-br br0 -- set Bridge br0 datapath_type=netdev > > ip netns add at_ns0 > ip link add p0 type veth peer name afxdp-p0 > ip link set p0 netns at_ns0 > ip link set dev afxdp-p0 up > > ovs-vsctl add-port br0 afxdp-p0 > ovs-vsctl -- set interface afxdp-p0 options:n_rxq=1 type="afxdp" > options:xdp-mode=native > > ip netns exec at_ns0 sh << NS_EXEC_HEREDOC > ip addr add "10.1.1.1/24" dev p0 > ip link set dev p0 up > NS_EXEC_HEREDOC > > ovs-vsctl -- set interface br0 options:n_rxq=1 type="afxdp" > options:xdp-mode=native
I'm not sure if this is a valid thing to do. After changing the netdev type this device is no linger TAP device. Now it's a permanent tap device that detached from any application and opened by af_xdp from the other side. BTW, changing the type of "internal" port doesn't sound safe. > ip addr add "10.1.1.2/24" dev br0 > ip link set dev br0 up > > # UDP works ok > ip netns exec at_ns0 nc -u -l 1234 > nc -u 10.1.1.1 1234 > <works ok> > > # TCP still fails > ip netns exec at_ns0 nc -l 1234 > nc 10.1.1.1 1234 > <no reponse> > _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev