On 16/09/2020 22:36, Adrian Chadd wrote:
On Wed, 16 Sep 2020 at 13:41, James Wright <[email protected]
<mailto:[email protected]>> wrote:
Hi wireless gurus,
I'm trying to understand why this USB wifi dongle is so slow under
FreeBSD.
The max real-world download rate seems to be capped at ~900KB/sec (see wget
below),
but with exactly the same hardware and conditions under Win10 I reach
~3MB/sec.
OS: FreeBSD 12.2-PRERELEASE (r365055)
Router: Virgin Media SuperHub 3 (802.11a/b/g/n/ac)
Hardware: Edimax EW-7811Un (RTL8188CUS)
Driver: rtwn
% grep wlan /etc/rc.conf
wlans_rtwn0="wlan0"
ifconfig_wlan0="WPA SYNCDHCP"
create_args_wlan0="country GB
% dmesg | grep rtwn
rtwn0 on uhub0
rtwn0: <Realtek 802.11n WLAN Adapter, class 0/0, rev 2.00/2.00, addr 1> on
usbus0
rtwn0: MAC/BB RTL8188CUS, RF 6052 1T1R
% sysctl dev.rtwn
dev.rtwn.0.rx_buf_size: 24
dev.rtwn.0.ratectl_selected: 1
dev.rtwn.0.ratectl: 1
dev.rtwn.0.hwcrypto: 1
dev.rtwn.0.debug: 0
dev.rtwn.0.ht40: 0
dev.rtwn.0.%parent: uhub0
dev.rtwn.0.%pnpinfo: vendor=0x7392 product=0x7811 devclass=0x00 devsubclass=0x00
devproto=0x00 sernum="00e04c000001"
release=0x0200 mode=host intclass=0xff intsubclass=0xff intprotocol=0xff
dev.rtwn.0.%location: bus=0 hubaddr=1 port=1 devaddr=2 interface=0
ugen=ugen0.2
dev.rtwn.0.%driver: rtwn
dev.rtwn.0.%desc: Realtek 802.11n WLAN Adapter, class 0/0, rev 2.00/2.00,
addr 1
dev.rtwn.%parent:
% ifconfig wlan0
wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
ether 74:da:38:8b:e1:10
inet 192.168.0.12 netmask 0xffffff00 broadcast 192.168.0.255
groups: wlan
ssid VM5909357 channel 6 (2437 MHz 11g ht/20) bssid
c0:05:c2:57:8d:69
regdomain ETSI country GB authmode WPA2/802.11i privacy ON
deftxkey UNDEF AES-CCM 2:128-bit AES-CCM 3:128-bit txpower 30
bmiss 7
scanvalid 60 protmode CTS ht20 ampdulimit 64k ampdudensity 8
shortgi
-stbc -ldpc wme roaming MANUAL
media: IEEE 802.11 Wireless Ethernet MCS mode 11ng
status: associated
nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
% ifconfig wlan0 scan
SSID/MESH ID BSSID CHAN RATE S:N
INT CAPS
VM5909357 c0:05:c2:57:8d:69 6 54M -78:-95
100 EPS HTCAP WME ATH RSN
% ifconfig wlan0 list sta
ADDR AID CHAN RATE RSSI IDLE TXSEQ RXSEQ CAPS FLAG
c0:05:c2:57:8d:69 1 6 65M 21.5 0 28562 4816 EPS AQEHTRs HTCAP
WME ATH RSN (rssi 0.0:0.0:0.0:0.0 nf
0:0:0:0)
% wget
https://download.freebsd.org/ftp/releases/amd64/amd64/ISO-IMAGES/12.1/FreeBSD-12.1-RELEASE-amd64-dvd1.iso
FreeBSD-12.1-RELEASE-amd64-dvd1.iso
<https://download.freebsd.org/ftp/releases/amd64/amd64/ISO-IMAGES/12.1/FreeBSD-12.1-RELEASE-amd64-dvd1.isoFreeBSD-12.1-RELEASE-amd64-dvd1.iso>
0%[ ] 19.05M 947KB/s eta 79m 18s
% wlandebug +rate
$ dmesg
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 6, txcnt=11, retrycnt=6
wlan0: [c0:05:c2:57:8d:69] AMRR decreasing rate 5 (txcnt=11 retrycnt=6)
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 5, txcnt=36, retrycnt=1
wlan0: [c0:05:c2:57:8d:69] AMRR increasing rate 6 (txcnt=36 retrycnt=1)
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 6, txcnt=37, retrycnt=7
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 6, txcnt=36, retrycnt=9
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 6, txcnt=36, retrycnt=2
wlan0: [c0:05:c2:57:8d:69] AMRR increasing rate 7 (txcnt=36 retrycnt=2)
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 7, txcnt=36, retrycnt=5
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 7, txcnt=36, retrycnt=5
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 7, txcnt=37, retrycnt=12
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 7, txcnt=36, retrycnt=7
wlan0: [c0:05:c2:57:8d:69] AMRR: current rate 7, txcnt=36, retrycnt=10
As you can see the MCS rate is being set by wlan_amrr to MCS 6 and 7, but
the actual real-world download rate
remains firmly stuck at around ~900KB/sec (!)
Please could someone with knowledge of the FreebSD wifi stack help diagnose
this problem with me?
hi!
You can experiment with limiting the unicast rate - eg ifconfig wlan0 ucastrate
3 for MCS3 when it's in 11n mode.
AMRR isn't the best at all at 802.11n rate selection. It may just be
over-estimating how great the channel is behaving.
However, that's just the transmit rate control. The remote end (ie the sender) is making choices on what rate to use
when transmitting to you. So let's see if we can first limit bad choices (and thus taking up too much airtime)
transmitting data BACK, and then we can figure out what's up with download speeds.
-adrian
Hi Adrian, thanks for your time and the explanation, much appreciated!
I tried setting ucastrate 3 and it made no difference to the download rate;
% ifconfig wlan0
wlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
ether 74:da:38:8b:e1:10
inet 192.168.0.12 netmask 0xffffff00 broadcast 192.168.0.255
groups: wlan
ssid VM5909357 channel 6 (2437 MHz 11g ht/20) bssid c0:05:c2:57:8d:69
regdomain ETSI country GB authmode WPA2/802.11i privacy ON
deftxkey UNDEF AES-CCM 2:128-bit AES-CCM 3:128-bit txpower 30 bmiss 7
ucastrate 3 scanvalid 60 protmode CTS ht20 ampdulimit 64k
ampdudensity 8 shortgi -stbc -ldpc wme roaming MANUAL
media: IEEE 802.11 Wireless Ethernet MCS mode 11ng
status: associated
nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
% wget
https://download.freebsd.org/ftp/releases/amd64/amd64/ISO-IMAGES/12.1/FreeBSD-12.1-RELEASE-amd64-dvd1.iso
FreeBSD-12.1-RELEASE-amd64-dvd1.iso. 0%[ ]
8.87M 806KB/s eta 81m 35s
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