#22127: WMM massively slows down ath9k in 4addr mode
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Reporter: vydriduch@… | Owner: developers
Type: defect | Status: new
Priority: normal | Milestone:
Component: kernel | Version: Trunk
Keywords: 4addr ath9k wmm performance |
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Hello
I am running Designated Driver r49089 on TP-Link WDR4900 (target mpc85xx).
I have set up a bridge on a client and connected it to the AP using the
4addr mode on a 2.4 GHz network configured with WPA2-PSK.
The client is a PC with an adapter that identifies as "Qualcomm Atheros
AR5418 Wireless Network Adapter [AR5008E 802.11(a)bgn] (PCI-Express) (rev
01)". Both the client and the server are ath9k devices. The client
(x86_64) runs Ubuntu Xenial with kernel 4.4.0.
If WMM is enabled on the AP, the bridged 4addr setup performs very poorly.
Measuring using iperf between the AP and the client, I get:
WMM off (802.11g):
19.4 Mbits/sec
WMM on (802.11n):
3.17 Mbits/sec
In contrast, when the same two machines are configured as "ordinary" AP
and client (4addr off) the speeds are as follows:
WMM off (802.11g):
19.7 Mbits/sec
WMM on (802.11n):
41.6 Mbits/sec
The use of the 4addr mode reduces the throughput by more than 90% compared
to an identical setup without 4addr mode, unless I limit myself to
802.11g. In that case the 4addr mode makes no difference.
The only parameters varied on the AP when taking the measurements were
'option wmm' and 'option wds'. The only relevant parameter (apart from
using a bridge) varied on the client was 4addr on/off.
The problems persist if I swap the server and client, i.e. run hostapd on
the PC and wpa_supplicant on the TP-Link device.
I have compiled OpenWrt with ath9k debugging enabled, but I do not quite
know what to look for.
--
Ticket URL: <https://dev.openwrt.org/ticket/22127>
OpenWrt <http://openwrt.org>
Opensource Wireless Router Technology
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