[Make-wifi-fast] graphing airtime fairness in wifi

David Lang david at lang.hm
Mon Apr 18 20:01:09 EDT 2016

On Mon, 18 Apr 2016, Dave Taht wrote:

>> (and there will be a large chunk
>> of airtime unused for various reasons, much of which you will not be able to
>> attribute to any one station, and if you do get full transmit data from each
>> station, you can end up with >100% airtime use attempted)
> The "black" lines on the pie chart would represent the interframe gap,
> you could use a color for "other things" like mgmt frames or
> interference (if you have the data), go "grey" or transparent for
> unused txops.
> I really wanted to be able to show the "pulse" that multicast
> powersave induces every ~250ms (could also use that to change the
> chart to show what stations are active), and pulses like upnp and
> other big pieces of multicast traffic can induce, also, by making the
> whole pie chart flash for the actual duration it took, while the sweep
> hand went 'round.

well, in the 'river' chart, such pulses are going to stand out as well (assuming 
you are displaying things to a suitable resolution.

Trying to have them show up in a pie chart seems hard. Are you really going to 
update the entire pie chart 4 times/sec? how is anyone going to see what's what 
when things are changing that fast?

> Similarly, mu-mimo "soundings" - although they are very short, could
> be shown, and I dunno how to show multiple stations going at once in
> that mode.
> (the spec suggests soundings be taken every 10ms (and take up to
> 500usec!!!), which is nuts. First you need per-station airtime
> scheduling and queuing, then, IF you have MU-mimo capable stations
> with data waiting for them, sound... and even then the only major
> cases where I think this feature is going to help all that much is in
> very, very dense environments, which have other problems)
>> I would be looking at a stacked area graph to show changes over time (a
>> particular source will come and go over time)
>> I would either do two graphs, one showing data successfully transmitted, the
>> other showing airtime used (keeping colors/order matching between the two
>> graphs), or if you have few enough stations, one graph with good lines
>> between the stations and have the color represent the % of theoretical peak
>> data transmission to show the relative efficiency of the different stations.
> Noted.
>> While the radar sweep updating of a pie graph is a neat graphic, it doesn't
>> really let you see what's happening over time.
> Disagree. At least on a testbench I'm pretty sure a "good" pattern
> could be recognisable against other traffic.

what information do we need to test this?

We've got the reports from /sys for the scale APs, is this sufficient? or do you 
really need something reporting >once/sec?

David Lang

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