Re: [PATCHv4 bpf-next 0/2] xdp: add dev map multicast support

Hangbin Liu [off-list ref] writes:

On Thu, Jun 04, 2020 at 02:37:23PM +0200, Toke Høiland-Jørgensen wrote:

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Now I use the ethtool_stats.pl to count forwarding speed and here is the result:

With kernel 5.7(ingress i40e, egress i40e)
XDP:
bridge: 1.8M PPS
xdp_redirect_map:
  generic mode: 1.9M PPS
  driver mode: 10.4M PPS

Ah, now we're getting somewhere! :)

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Kernel 5.7 + my patch(ingress i40e, egress i40e)
bridge: 1.8M
xdp_redirect_map:
  generic mode: 1.86M PPS
  driver mode: 10.17M PPS

Right, so this corresponds to a ~2ns overhead (10**9/10400000 -
10**9/10170000). This is not too far from being in the noise, I suppose;
is the difference consistent?

Sorry, I didn't get, what different consistent do you mean?

I meant, how much do the numbers vary between each test run?

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xdp_redirect_map_multi:
  generic mode: 1.53M PPS
  driver mode: 7.22M PPS

Kernel 5.7 + my patch(ingress i40e, egress veth)
xdp_redirect_map:
  generic mode: 1.38M PPS
  driver mode: 4.15M PPS
xdp_redirect_map_multi:
  generic mode: 1.13M PPS
  driver mode: 3.55M PPS

With XDP_DROP in veth perr, the number looks much better

xdp_redirect_map:
  generic mode: 1.64M PPS
  driver mode: 13.3M PPS
xdp_redirect_map_multi:
  generic mode: 1.29M PPS
  driver mode: 8.5M PPS

Is this for a single interface in both cases? Look a bit odd that you
get such a big difference all of a sudden; is the redirect failing in
one of those cases (should be a hint in the ethtool stats, I think,
otherwise check xdp_monitor)?

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Kernel 5.7 + my patch(ingress i40e, egress i40e + veth)
xdp_redirect_map_multi:
  generic mode: 1.13M PPS
  driver mode: 3.47M PPS

But I don't know why this one get even a little slower..

xdp_redirect_map_multi:
  generic mode: 0.96M PPS
  driver mode: 3.14M PPS

Yeah, this does seem a bit odd. Don't have any good ideas off the top of
my head, but maybe worth double-checking where the time is spent. You
can use 'perf' for this, but you need to make sure it's recording the
CPU that is processing packets...

-Toke