[Codel] [Bloat] The challenge

[Eric Dumazet]

On Wed, 2012-05-16 at 08:55 +0300, Jonathan Morton wrote:
> On 9 May, 2012, at 4:04 pm, Kevin Gross wrote:
> 
> > From the paper (figure 7), you can see that CoDel still leaves spikes of buffer occupancy when network conditions change. These will still be disruptive to real-time traffic. Many networks that need QoS now will still need QoS. Networks that do not have QoS will be much more usable with CoDel.
> 
> Combining AQM with FQ certainly seems like a good idea to me.  I haven't had a chance to try the implementation of fq_codel which already exists yet, but it's compiled and just waiting for me to get around to it.  If it works, then it should be an excellent default.


fq_codel has no priority concepts. It's only Fair. But what is
Fairness ?

In the presence of elephant flows, you get more packets drops from
elephant flows than from thin ones.

If the elephant flow is the 'high priority' traffic, dropping packets
from it is not what you wanted.

pfifo_fast is able to have strict priority. If you want Codel and strict
priority, you can use prio + codel  (or prio + fq_codel)