[Make-wifi-fast] [PATCH v8 0/2] Implement Airtime-based Queue Limit (AQL)

Toke Høiland-Jørgensen toke at redhat.com
Tue Nov 26 04:19:43 EST 2019

Kan Yan <kyan at google.com> writes:

>> Yeah, bpftrace can be a bit of a pain to get running; but it may be
>> worth the investment longer term as well. It really is quite useful! :)
> My attempt to build bpftrace didn't work out, so I just got the
> sojourn time using old fashioned trace event.
> The raw trace, parsed data in csv format and plots can be found here:
> https://drive.google.com/open?id=1Mg_wHu7elYAdkXz4u--42qGCVE1nrILV
> All tests are done with 2 TCP download sessions that oversubscribed
> the link bandwidth.
> With AQL on, the mean sojourn time about ~20000us, matches the default
> codel "target".

Yeah, since CoDel is trying to control the latency to 20ms, it makes
sense that the value is clustered around that. That means that the
algorithm is working as they're supposed to :)

While you're running tests, could you do one with the target changed to
10ms, just to see what it looks like? Both sojourn time values and
throughput would be interesting here, of course.

> With AQL off, the mean sojourn time is less than 4us even the latency
> is off the charts, just as we expected that fd_codel with mac80211
> alone is not effective for drivers with deep firmware/hardware queues.

Yup, also kinda expected; but another good way to visualise the impact.


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