[ath9k-devel] Low throughput AR9280 HT40+

[Stephen Donecker <sdonecker@ahmct.ucdavis.edu>]

Hi,

I appear to be getting lower throughput than I should be between two 
single stream adhoc nodes (~78Mbps UDP). Shouldn't I be getting closer 
to ~128Mbps? Could someone explain why such a high ratio of lost 
datagrams? When looking through the list the vast majority of people get 
a very small datagram loss.

Hardware:
Ubiquity Routerstation (AR7161)
Ubiquity SR71-15 (AR9280)
OpenWRT r32062 (linux-3.3.8, compat-wireless-2012-05-29)

Config:
# cat /sys/kernel/debug/ieee80211/phy0/frequency
5785
# cat /sys/kernel/debug/ieee80211/phy0/channel_type
ht40+
# cat /sys/kernel/debug/ieee80211/phy0/ath9k/tx_chainmask
0x00000001
# cat /sys/kernel/debug/ieee80211/phy0/ath9k/rx_chainmask
0x00000001

Throughput test:
# iperf -c 192.168.11.2 -p 7777 -u -b 150m -t 10 -i 1
------------------------------------------------------------
Client connecting to 192.168.11.2, UDP port 7777
Sending 1470 byte datagrams
UDP buffer size:  160 KByte (default)
------------------------------------------------------------
[  3] local 192.168.11.1 port 47537 connected with 192.168.11.2 port 7777
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec  15.3 MBytes   128 Mbits/sec
[  3]  1.0- 2.0 sec  15.1 MBytes   126 Mbits/sec
[  3]  2.0- 3.0 sec  15.3 MBytes   128 Mbits/sec
[  3]  3.0- 4.0 sec  15.3 MBytes   128 Mbits/sec
[  3]  4.0- 5.0 sec  15.4 MBytes   129 Mbits/sec
[  3]  5.0- 6.0 sec  15.3 MBytes   129 Mbits/sec
[  3]  6.0- 7.0 sec  15.3 MBytes   128 Mbits/sec
[  3]  7.0- 8.0 sec  15.2 MBytes   128 Mbits/sec
[  3]  8.0- 9.0 sec  15.3 MBytes   128 Mbits/sec
[  3]  0.0-10.0 sec   153 MBytes   128 Mbits/sec
[  3] Sent 108972 datagrams
[  3] Server Report:
[  3]  0.0-10.0 sec  92.9 MBytes  77.8 Mbits/sec   0.243 ms 42715/108973 
(39%)

# iw dev wlan0 station dump
Station 00:15:6d:85:0f:78 (on wlan0)
     inactive time:    170 ms
     rx bytes:    102078921
     rx packets:    85286
     tx bytes:    1412173463
     tx packets:    921845
     tx retries:    209
     tx failed:    0
     signal:      -56 [-56] dBm
     signal avg:    -55 [-55] dBm
     tx bitrate:    150.0 MBit/s MCS 7 40Mhz short GI
     rx bitrate:    150.0 MBit/s MCS 7 40Mhz short GI
     authorized:    yes
     authenticated:    yes
     preamble:    long
     WMM/WME:    yes
     MFP:        no
     TDLS peer:    no

Thanks,

-Stephen

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