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

[Dave Taht <dave.taht@gmail.com>]

On Wed, Aug 10, 2016 at 11:50 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> Toke Høiland-Jørgensen <toke@toke.dk> writes:
>
>> On 10 August 2016 21:35:40 CEST, Dave Taht <dave.taht@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.

But there are tons of drops evident from the captures.

> 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



-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org