[FS#44] Ath9k - TX performance regression on greater coverage settings

[LEDE Bugs]

The following task has a new comment added:

FS#44 - Ath9k - TX performance regression on greater coverage settings
User who did this - Bluse-Blue (Bluse)

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Hi Koen,

I just set up a two router experiment on my desk.
Lastest LEDE HEAD, r1227 on both. 
2,4 GHz HT20, Laptop_A ->ETHERNET-> AP -> STA ->ETHERNET-> Laptop_B
Router-A: PCengies APU 2c4 & Microtik 2x2 ath9k
Router-B: TPLink tl-wr1042 v3 3x3 ath9k
on Laptop A: iperf -s -u
on Laptop B: iperf -c IP(Laptop_A) -u -l 1400 -b 100M -t 30

on AP: disbale Misntrel_HT ratecontrol and set fixed rate to MSC 15 
echo 72 > /sys/kernel/debug/ieee80211/phy0/rc/fixed_rate_idx

scenario 1: distance set to 50
udp throughput is ~42MBit/s
aggregates ~ 4000 (from xmit)
max frames per aggregate: 32 (from /sys/kernel/debug/ieee80211/phy0/netdev\:wlan0/stations/MAC_ADRESS/rc_stats)

scenario 1: distance set to 14000
udp throughput is ~20MBit/s
aggregates ~ 2000 (from xmit)
max frames per aggregate: 31 (from /sys/kernel/debug/ieee80211/phy0/netdev\:wlan0/stations/MAC_Adress/rc_stats)

So throughput got have when I go to 14000m and aggragation shows the same amount of packets per aggregate and obviously half of overall aggregates as throughput is als half.

Greetings from Berlin
Bluse
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=44#comment182