On Tue, Nov 19, 2019 at 09:26:40PM +0100, Ilya Maximets wrote: > On 19.11.2019 21:09, William Tu wrote: > > On Tue, Nov 19, 2019 at 08:51:19PM +0100, Ilya Maximets wrote: > >> 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. > > > > I see, thanks. > > > > Then if we don't change br0 to afxdp type, the TCP test > > below still fails, which I think should pass because > > we are using native mode for veth now. > > > > I think even native mode doesn't work for TCP? > > Disable Tx offloading on both p0 and br0 and it will work.
So is it because when doing tx, af_xdp dev does not support tcp checksum offload, so kernel is dropping tcp packet? William _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev