Re: Packet throughput (and those iperf data rate) with mac80211/ath9k is 20% worse than net80211/madwifi

["Toke Høiland-Jørgensen" <toke@toke.dk>]

Klaus Kinski <jpo234-1ViLX0X+lBKELgA04lAiVw@public.gmane.org> 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