[Cake] Upstream submission of dual-mode fairness patch

[Toke Høiland-Jørgensen]

Pete Heist <pete at heistp.net> writes:

> Thanks for the nudge... I just tested this on the original one-armed
> router setup I encountered it on (3.16.7, routing from eth0 to
> eth0.3300). The patch makes a big improvement over the original (which
> was around 10/80):
>
> IP 1, 1 up: 47.0 Mbit
> IP 2, 8 up: 47.0 Mbit
> IP 1, 8 down: 46.7 Mbit
> IP 2, 1 down: 46.6 Mbit
>
> Curiously, if my one-armed router has cake applied on egress and
> ingress of eth0.3300, instead of egress of eth0 and egress of
> eth0.3300 as above, some reduction in fairness occurs, but only for
> the downstream flows. This increases with the number of flows:
>
> IP 1, 1 up: 47.2 Mbit
> IP 2, 8 up: 47.2 Mbit
> IP 1, 8 down: 44.5 Mbit
> IP 2, 1 down: 48.7 Mbit
>
> IP 1, 1 up: 47.0 Mbit
> IP 2, 16 up: 47.0 Mbit
> IP 1, 16 down: 42.6 Mbit
> IP 2, 1 down: 50.3 Mbit
>
> IP 1, 1 up: 47.2 Mbit
> IP 2, 32 up: 47.0 Mbit
> IP 1, 32 down: 41.4 Mbit
> IP 2, 1 down: 51.3 Mbit
>
> It still happens when ether-vlan is used on the leaf qdiscs with vlan
> traffic.

Hmm, I have no good explanation for this...

> That said, unless there’s an obvious reason for this that’s fixable,
> I’m fine with how it is, considering the improvement. :)

Cool! And you haven't seen any regressions in other usage? :)

-Toke