[Cake] [Make-wifi-fast] Flent results for point-to-point Wi-Fi on LEDE/OM2P-HS available

Toke Høiland-Jørgensen toke at toke.dk
Mon Jan 30 16:44:55 EST 2017

Pete Heist <peteheist at gmail.com> writes:

> Hi, I’ve posted some Flent results and analysis for point-to-point Wi-Fi using LEDE on OM2P-HS (ath9k):
> http://www.drhleny.cz/bufferbloat/wifi_bufferbloat.html

Oh my, this is quite a lot of tests. Nice :)

Few general points on running tests:

- Yeah, as you note Flent has a batch facility. Did you not use this
  simply because you couldn't find it, or was there some other reason?
  Would love some feedback on what I can do to make that more useful to
  people... While I have no doubt that your 'flenter.py' works, wrapping
  a wrapper in this sense makes me cringe a little bit ;)

- Flent also has a metadata gathering feature where you can get lots of
  stats from both your qdisc-based bottlenecks, and your WiFi links.

- I'm not sure if you're checking that applying your qdiscs actually
  works? For the WiFi interfaces with 'noqueue' you *cannot* apply a
  different qdisc (which also answers your question #2).

> Over 500 runs were done using different configurations, as the effects
> of various changes were explored. In case someone has the time to
> respond, there are a number of questions in red. Whatever feedback I
> get I’ll try to incorporate into a final document. Also, if I’ve made
> any false assertions I’d love to hear about it.

I don't have time to go through your whole document now, but a few

Question 1 (and partly #13): Yeah, the version of LEDE you're running
already has the FQ-CoDel-based queueing in the ath9k driver. The
baseline you're seeing is consistent with the results we've been getting
in testing. This is also seen by any gains you get being paired with
quite a hefty hit in throughput. So with this driver, I would say it's
not worth it. However, this is going to be different on a setup without
the WiFi queueing fixes.

Question 5: For TCP you can't get packet loss from user space; you'll
need packet captures for that. So no way to get it from Flent either.
You can, however, get average throughput. Look at the box plots; if you
run multiple iterations of the same test, you can plot several data
files in a single box_combine plot, to get error bars. `flent
file.flent.gz -f summary` (which is the default if you don't specify a
plot) will get you averages per data series; or you can extract it from
the metadata.


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