[Olsr-users] Fwd: Question about hidden node behavior

[Juliusz Chroboczek]

> So far i haven't seen a hw queue filled, they are emptied really fast,
> not even on multi-bssid scenarios,

Think a while about what that means.

Assuming the driver has finite storage, then either the driver is able
to exert backpressure (i.e. cause a queue to build up in the kernel), or
it must drop packets.  There's just no way around it -- the packets must
go somewhere.

What Nick is saying is that ath9k doesn't normally drop packets.  Hence,
it must apply backpressure somewhere.  If my understanding is correct,
this happens in ath9k/xmit.c around line 1768.

As far as my understanding of Linux packet scheduling goes, this should
in principle be good enough to perform shaping without throttling with
ath9k.  Note however that the ath9k driver maintains fairly large queues
(the low mark is set at 123 packets), so I'm not sure how effective
shaping will be with this particular driver.

                                        Juliusz