On 7/14/20 6:29 AM, Toke Høiland-Jørgensen wrote: > Hangbin Liu <liuhangbin@xxxxxxxxx> writes: > >> This patch is for xdp multicast support. which has been discussed before[0], >> The goal is to be able to implement an OVS-like data plane in XDP, i.e., >> a software switch that can forward XDP frames to multiple ports. >> >> To achieve this, an application needs to specify a group of interfaces >> to forward a packet to. It is also common to want to exclude one or more >> physical interfaces from the forwarding operation - e.g., to forward a >> packet to all interfaces in the multicast group except the interface it >> arrived on. While this could be done simply by adding more groups, this >> quickly leads to a combinatorial explosion in the number of groups an >> application has to maintain. >> >> To avoid the combinatorial explosion, we propose to include the ability >> to specify an "exclude group" as part of the forwarding operation. This >> needs to be a group (instead of just a single port index), because there >> may have multi interfaces you want to exclude. >> >> Thus, the logical forwarding operation becomes a "set difference" >> operation, i.e. "forward to all ports in group A that are not also in >> group B". This series implements such an operation using device maps to >> represent the groups. This means that the XDP program specifies two >> device maps, one containing the list of netdevs to redirect to, and the >> other containing the exclude list. >> >> To achieve this, I re-implement a new helper bpf_redirect_map_multi() >> to accept two maps, the forwarding map and exclude map. If user >> don't want to use exclude map and just want simply stop redirecting back >> to ingress device, they can use flag BPF_F_EXCLUDE_INGRESS. >> >> The 2nd and 3rd patches are for usage sample and testing purpose, so there >> is no effort has been made on performance optimisation. I did same tests >> with pktgen(pkt size 64) to compire with xdp_redirect_map(). Here is the >> test result(the veth peer has a dummy xdp program with XDP_DROP directly): >> >> Version | Test | Native | Generic >> 5.8 rc1 | xdp_redirect_map i40e->i40e | 10.0M | 1.9M >> 5.8 rc1 | xdp_redirect_map i40e->veth | 12.7M | 1.6M >> 5.8 rc1 + patch | xdp_redirect_map i40e->i40e | 10.0M | 1.9M >> 5.8 rc1 + patch | xdp_redirect_map i40e->veth | 12.3M | 1.6M >> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e | 7.2M | 1.5M >> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->veth | 8.5M | 1.3M >> 5.8 rc1 + patch | xdp_redirect_map_multi i40e->i40e+veth | 3.0M | 0.98M >> >> The bpf_redirect_map_multi() is slower than bpf_redirect_map() as we loop >> the arrays and do clone skb/xdpf. The native path is slower than generic >> path as we send skbs by pktgen. So the result looks reasonable. >> >> Last but not least, thanks a lot to Jiri, Eelco, Toke and Jesper for >> suggestions and help on implementation. >> >> [0] https://xdp-project.net/#Handling-multicast >> >> v7: Fix helper flag check >> Limit the *ex_map* to use DEVMAP_HASH only and update function >> dev_in_exclude_map() to get better performance. > > Did it help? The performance numbers in the table above are the same as > in v6... > If there is only 1 entry in the exclude map, then the numbers should be about the same.
