From: Klaus Kinski <jpo234@outlook.de>
To: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: Packet throughput (and those iperf data rate) with mac80211/ath9k is
 20% worse than net80211/madwifi
Date: Mon, 30 Jan 2017 15:57:08 +0000
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Sender: linux-wireless-owner@vger.kernel.org

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:


Data rate  madwifi  %of total ath9k minstrel %of total

6.0        855      2,31        37              0,12
9.0        0          0,00        22                0,07
12.0      0          0,00      23                0,07
18.0          0          0,00        20                0,06
24.0          9          0,02        21                0,07
36.0          855        2,31        20                0,06
48.0          856        2,31        24                0,08
54.0          34413      93,04      31566                99,47
total      36988     100,00      31733                100,00


It shows how many packets where sent at what data rate and the percentage of these packets
from the total. Both stacks are sending most packets with 54Mbit/s (93% and 99%).

Overall Madwifi sends 36988 (= 100%) data packets whereas mac80211 only sends 31733 (= 85%) data packets.

Does anybody know where this difference comes from? It's not the CPU; both systems

have plenty enough for the task. I'm pretty sure that the reason is in the stack,

probably mac80211.

I have asked basically the same question almost 6 years ago (see http://narkive.com/F8xI8bUp.1 ).

An interesting proposal at that time came from Adrian Chadd in http://narkive.com/F8xI8bUp.15:

  does madwifi have that net80211 "aggressive mode" by default, where it

  overrides the best-effort WME queue parameters to allow for bursting?

I could not find a mac80211 option to control this "aggressive mode". Is there one? Or a patch

to test it out?

Thanks in advance
  Joerg