#16997: Throughput Drop in Later Revisions of OpenWrt on TL-WR842ND V1
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Reporter: furryfur1@… | Owner: developers
Type: defect | Status: new
Priority: high | Milestone: Barrier Breaker (trunk)
Component: kernel | Version: Trunk
Keywords: |
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This issue is present in both Barrier Breaker trunk and the latest
revisions of AA built from the git repository. The throughput drop occurs
when going from r37917 to r37918 or any later revision in the BB trunk,
r37917 does not exhibit the throughput drop but all later revisions do.
The throughput drop also occurs when going from AA revision r39927 to
r39928 or later. The throughput drop is about 10Mbps in my test-bed:
between two routers, the transmitting router in WDS mode, both running
OpenWrt, the main transmit router is a TL-WR842ND V1 and is the only one I
changed firmware on to try to narrow down which revisions were causing the
drop. I patched each revision before building it with my 40MHz WDS patch
(stop wpa_supplicant locking hostapd to 20MHz, #12720) so that the test
was fair against later revisions which have this patch, as it affects
throughput. I also tested throughput between the main transmit router and
other devices (Android tablet running iperf, 20MHz only, not compatible
with my upper channel) and noted I also got reduced throughput here,
although not as much as the devices were a lot closer. I am using reghack
to unlock channel 13 which should be available in my country on each
build.
The iperf command from the main transmit router was as follows: iperf -w
320k -t 30 -c 192.168.2.3. The iperf command on the receiving router was
as follows: iperf -w 320k -s. An example of the throughput difference
between revisions is as follows: Transmitter (trunk r41181) ---> Receiver
(AA r36088) : 32.6Mbps; Transmitter (AA r36088) ---> Receiver (AA r36088)
: 43.5Mbps. I did not record all my experiments however they were
consistent on affected revisions, dropping about 10Mbps.
This router is also connected via WDS to another upstream router which I
used to establish that changing revisions did not affect receive
throughput, only transmitter throughput (throughput from upstream router
seems to stay the same no matter what revision I use on the downstream). I
notice an overall reduced throughput in my internet throughput which comes
from the upstream router as well (upstream running BB r41181, also on a
TL-WR842ND V1).
/etc/config/wireless for main transmit router
config wifi-device 'radio0'
option type 'mac80211'
option macaddr '90:f6:52:78:19:4c'
option hwmode '11ng'
list ht_capab 'SHORT-GI-20'
list ht_capab 'SHORT-GI-40'
list ht_capab 'TX-STBC'
list ht_capab 'RX-STBC1'
list ht_capab 'DSSS_CCK-40'
option rts '500'
option channel '9'
option htmode 'HT40+'
option noscan '1'
option log_level '1'
option distance '185'
option txpower '21'
option country '00'
config wifi-iface
option ssid 'UKD'
option device 'radio0'
option mode 'sta'
option key '#######'
option wds '1'
option encryption 'psk2+ccmp'
option network 'lan'
option bssid 'A2:F3:C1:9C:F8:76'
config wifi-iface
option device 'radio0'
option mode 'ap'
option ssid 'UKD'
option wds '1'
option network 'lan'
option encryption 'psk2+ccmp'
option key '#######'
--
Ticket URL: <https://dev.openwrt.org/ticket/16997>
OpenWrt <http://openwrt.org>
Opensource Wireless Router Technology
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