[Bloat] [Codel] Exploring the potential of codel, fq_codel, and qfq

[Eric Dumazet]

On Wed, 2012-05-16 at 10:40 -0700, Rick Jones wrote:

> 
> I like netperf as much as anyone :)  but keep in mind that the TCP_RR 
> test has only one segment outstanding at a time only when the 
> request/response size is < MSS and/or one has not enabled burst mode to 
> have multiple transactions in flight at one time.
> 
> Are we really likely to see a situation where all the flows are one 
> packet at a time?   If all the flows are either that way naturally, or 
> have gotten there thanks to a one segment cwnd are we not already in a 
> very pathological situation?
> 
> For the impossible to define "fair" question, is it fair to drop a 
> flow's only packet if there are other, multiple-packet flows around?

Please take a look at the patch I sent some hours ago.

In fact the real problem was that thin flows were bypassing codel algo
because we considered the flow backlog (one packet) and decided to _not_
drop packet regardless of its sojourn_time.

With the fix, there is no more problem : fq_codel downgrades to a codel
qdisc in case of a DDOS.