[Cerowrt-devel] [Bloat] great interview on the scale conference wifi successes

David Lang david at lang.hm
Thu Mar 12 20:53:59 EDT 2015

On Thu, 12 Mar 2015, Dave Taht wrote:

> so the wifi and ethernet queues are fq_codeled in this past SCALE.
> One little understood fact about aggregated' wifi is that you CAN
> actually FQ the faster rate ethernet queue with the theoretically
> slower rate wifi queue, because a wifi aggregate is decoded at memory
> speeds, not wire or wireless speeds, and thus, can fill the BQL
> ethernet driver queue and have packets stuck at the qdisc layer, where
> they can be handled more smartly.
> That said, don't know if that ever happened at scale without data.
> The wifi outgoing interfaces on each AP on the other hand, could very
> well have had either the fq or the codel portions of the algorithm
> engage... they certainly do on my tests here.
> Although dlang did get quite a lot of data (which I have not yet seen,
> or have I had time for - does anyone here have time to analyze it? He
> got a ton of minstrel statistics in particular), but I am unsure if he
> collected any of the tc -s qdisc data from the wifi interfaces. (?)

no, I missed/forgot the request for that.

it's about 20G of data uncompressed, I'm running lzma on it now to see how small 
it will shrink.

> I also have to note that the ath9k driver has got so good now, that a
> ton of the benefit at scale probably came from that, and a great deal
> more, from dlang's excellent design for the network itself. It is sad,
> of course, that useful functionality like sta-to-sta transfers has to
> be disabled in such environments nowadays.
> I am really sorry I couldn't go.
> I am seeing 25% better forwarding rates on ethernet out of 3.18 vs
> 3.10 on the same wndr 3800 hardware, btw.

hmm, does this have a noticable effect on the HTB throttling performance?

David Lang

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