Date: Wed, 16 Sep 2020 21:41:53 +0100 From: James Wright <james.wright@digital-chaos.com> To: freebsd-wireless@freebsd.org Subject: Edimax EW-7811Un (rtwn): Slow speeds / rate control Message-ID: <b76ded4d-135a-9e0f-d25e-44bcf664ddc2@digital-chaos.com>
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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 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?
Interestingly, if i disable ratectl in loader.conf, then i get a slightly higher capped rate of ~1.2MB/sec
but still much lower than what should be acheiveable from this network;
/boot/loader.conf;
if_rtwn_load="YES"
if_rtwn_usb_load="YES"
legal.realtek.license_ack=1
dev.rtwn.0.ratectl=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 0%[ ] 28.55M 1.18MB/s eta 64m 6s
Many Tahnks,
James
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