[Codel] fq_codel_drop vs a udp flood

[Dave Taht]

Thus far this batch drop patch is testing out beautifully. Under a
900Mbit flood going into 100Mbit on the pcengines apu2,  cpu usage for
ksoftirqd now doesn't crack 10%, where before (under
pie,pfifo,fq_codel,cake & the prior fq_codel) it went to 88% and
ultimately bad things happened, like losing routability.

I've had it running for hours and I hardly notice it's there.

Performance for the normal cc controlled and/or sparse flows is
unaffected, aside from the uncontrolled flows eating their percentage
of the link.

Nice work. Thx. This should go into -stable.

https://patchwork.ozlabs.org/patch/617307/

Sigh. The RFC is past last call...