Re: [PATCHv16 bpf-next 0/6] xdp: add a new helper for dev map multicast support

Toke Høiland-Jørgensen
2021-01-22T13:45:56Z

Hangbin Liu <liuhangbin@gmail.com> 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 1st patch is Jesper's run devmap xdp_prog later in bulking step.
> The 2st patch add a new bpf arg to allow NULL map pointer.
> The 3rd patch add the new bpf_redirect_map_multi() helper.
> The 4-6 patches are for usage sample and testing purpose.
>
> I did same perf tests with the following topo:
>
> --------------------- ---------------------
> | Host A (i40e 10G) | ---------- | eno1(i40e 10G) |
> --------------------- | |
> | Host B |
> --------------------- | |
> | Host C (i40e 10G) | ---------- | eno2(i40e 10G) |
> --------------------- vlan2 | -------- |
> | veth1 -- | veth0| |
> | -------- |
> --------------------|
> On Host A:
> # pktgen/pktgen_sample03_burst_single_flow.sh -i eno1 -d $dst_ip -m $dst_mac -s 64
>
> On Host B(Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz, 128G Memory):
> Use xdp_redirect_map and xdp_redirect_map_multi in samples/bpf for testing.
> The veth0 in netns load dummy drop program. The forward_map max_entries in
> xdp_redirect_map_multi is modify to 4.
>
> Here is the perf result with 5.10 rc6:
>
> The are about +/- 0.1M deviation for native testing
> Version | Test | Generic | Native | Native + 2nd
> 5.10 rc6 | xdp_redirect_map i40e->i40e | 2.0M | 9.1M | 8.0M
> 5.10 rc6 | xdp_redirect_map i40e->veth | 1.7M | 11.0M | 9.7M
> 5.10 rc6 + patch1 | xdp_redirect_map i40e->i40e | 2.0M | 9.5M | 7.5M
> 5.10 rc6 + patch1 | xdp_redirect_map i40e->veth | 1.7M | 11.6M | 9.1M
> 5.10 rc6 + patch1-6 | xdp_redirect_map i40e->i40e | 2.0M | 9.5M | 7.5M
> 5.10 rc6 + patch1-6 | xdp_redirect_map i40e->veth | 1.7M | 11.6M | 9.1M
> 5.10 rc6 + patch1-6 | xdp_redirect_map_multi i40e->i40e | 1.7M | 7.8M | 6.4M
> 5.10 rc6 + patch1-6 | xdp_redirect_map_multi i40e->veth | 1.4M | 9.3M | 7.5M
> 5.10 rc6 + patch1-6 | xdp_redirect_map_multi i40e->i40e+veth | 1.0M | 3.2M | 2.7M
>
> Last but not least, thanks a lot to Toke, Jesper, Jiri and Eelco for
> suggestions and help on implementation.

Nice work, and thank you for sticking with this! With the last couple of
fixes discussed for patch 1, when you resubmit please add my:

Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>

for the series!

-Toke