netdev - Re: [PATCHv7 bpf-next 0/3] xdp: add a new helper for dev map multicast support

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Date:   Wed, 15 Jul 2020 11:45:22 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Subject: Re: [PATCHv7 bpf-next 0/3] xdp: add a new helper for dev map
 multicast support

On Tue, Jul 14, 2020 at 11:12:59AM -0600, David Ahern wrote:
> >> 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.

Yes, I didn't re-run the test. Because when do the testing, I use null exclude
map + flag BPF_F_EXCLUDE_INGRESS. So the perf number should have no difference
with last patch.

Thanks
Hangbin