[Make-wifi-fast] On the 802.11 performance anomaly and an airtime fairness scheduler to fix it

Luca Muscariello luca.muscariello at gmail.com
Sun Jul 3 02:55:25 EDT 2016


great piece of work.
UDP tests show that the scheduler is working quite well.
TCP tests: no news that ACK streams are a problem.
This is another well known issue  in wifi.

Every data packet is ACKed already at L2 and L4
sends an ACK that is non contention free.

There is an NSDI paper in 2014 that proposes to use the L2 ACK to carry the
It works well but purists might hate that approach.

BTW the gains you show are huge.
If you add multiple stations uniformly distributed around the AP you'll see
tremendous gains.

The delay gain is also huge and poorly explored so far.

On Thu, Jun 30, 2016 at 11:06 PM, Toke Høiland-Jørgensen <toke at toke.dk
<javascript:_e(%7B%7D,'cvml','toke at toke.dk');>> wrote:

> I've previously posted my airtime fairness scheduler patch here. When I
> did I promised a more thorough performance evaluation of it. This took a
> bit longer to get done than I had anticipated, but I have now put up a
> blog post with some pretty graphs.
> The post also explains the background of the 802.11 performance anomaly
> to those not familiar with it; feel free to skip to the results if you
> are already familiar with it.
> Link:
> https://blog.tohojo.dk/2016/06/fixing-the-wifi-performance-anomaly-on-ath9k.html
> -Toke
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