[Cerowrt-devel] [Make-wifi-fast] wifi airtime fairness patches could use eyeballs and testing

[Toke Høiland-Jørgensen]

Toke Høiland-Jørgensen <toke at toke.dk> writes:

> On 10 August 2016 21:35:40 CEST, Dave Taht <dave.taht at gmail.com> wrote:
>>Wow, that *is* weird. It is good to see the tcp window changing on
>>this set of data (it wasn't before), and CWRs, but... hmmm... SCIENCE.
>>
>>Enabling ecn on both sides will rule out some potential bugs.
>
> Yeah, couldn't get ecn to work on the host I was using as the other endpoint on
> that test. Will try with another box that's not on quite as ancient a kernel.
> Was also planning to disable codel (by setting a very high target) to try to
> narrow down the problem.

OK, digging some more on this:

I am seeing *no* drops by CoDel, and no backlog in the mac80211 softq
layer either (or at most one or two packets when polling with a 1 sec
interval). This is with one as well as with two flows.

On my x86 testbed I see backlog building and packets getting dropped by
CoDel - and can't reproduce the performance hit. So I'm wondering what
the difference is. I can think of:

- Another bottleneck somewhere in the system limiting things on the
  wndr3800.

- A locking issue in the FQ mechanism preventing packets from being
  queued properly.

- Something related to the wndr only having a single CPU.

-Toke