Klaus Kinski [off-list ref] writes:

Hello all,

this is a blast from the past, but something that still bothers me.
I have two systems with Atheros/QCA cards:

System A:
  OS and driver: Linux 3.18.36 with last Madwifi/sample code from trunk

  WLAN card: AR5413 (Senao EMP-8602 PLUS-S)

System B:
  OS and driver: Linux 3.18.36 with mac80211/minstrel and ath9k from backports-4.2

  WLAN card: AR9280 (Compex WLE200NX)

While doing the performance measurements both systems are connected to a reference system

with a HF cable, so there should be no outside influences.

Both systems are running in 802.11a mode on channel 40.
The following table shows 802.11 data packets sent from system A and B generated by

iperf in UDP mode over a 2s interval:

What version of iperf, and configured to which rate? Some versions of
iperf will send its traffic in very large bursts (see
http://burntchrome.blogspot.se/2016/09/iperf3-and-microbursts.html?m=1)
which could cause the queue inside ath9k to overflow (it is only 123
packets pre-4.10).

Did you try the latest mac80211/ath9k from 4.10? The queueing structure
changed dramatically, which would impact this, at least if it's a queue
overflow problem...

-Toke