[RFC Patch v5 0/5] net_sched: introduce eBPF based Qdisc

On 06/24, sdf wrote:

I feel like this patch series (even rfc), should also have a good example

to show that bpf qdisc is on par and can be used to at least implement
existing policies.

I recently build an example for the simplest `pfifo` qdisc based on Cong Wang's patches, 
see https://github.com/Forsworns/sch_bpf/
if you have interests. The sample is a little large, and involving modifications on libbpf, 
so I didn't attach it as a patch here. 

I also run a micro-benchmark with iperf3, see 
https://gist.github.com/Forsworns/71b70ed67d2ac53a4316bac862ce7d0f

I know it's unfair to evaluate the sch_bpf with `pfifo`, since sch_bpf is based on rbtree.
But I think it a good example for other classiful and more complicated qdiscs.
The `pfifo` is simple enough as a start :)