[Codel] coping with memory limitations and packet flooding in codel and fq_codel

[Eric Dumazet]

On Sun, 2012-08-26 at 14:36 -0700, Dave Taht wrote:

> From looking over the history of this idea, it does seem to be a good
> idea for small devices with potentially big queues.
> 
> http://www.spinics.net/lists/netdev/msg176967.html
> 
> That said I do tend to agree with davem's summary in fixing the
> wifi drivers in the first place. The current allocation in the ath9k driver
> doesn't make any sense in the first place, which (to me) implies magic
> lies underneath that I'm reluctant to fiddle with, without deep knowledge
> of how the ath9k driver behaves with wep/wpa/ampdus, etc.
> 

Problem is some hardware cannot do this in a smart way, without paying
the price of a sometime expensive copy.

Thats why I refined this idea to actually trigger only if current
memory needs are above a threshold.

If packets are received and immediately consumed, without potentially
staying a long time in a queue, it doesnt really matter they use 200 or
400% more ram than the rightly sized packets.