Edimax EW-7811Un (rtwn): Slow speeds / rate control
James Wright
james.wright at digital-chaos.com
Wed Sep 16 23:01:08 UTC 2020
This build is from stable/12 rather than HEAD, so it may not be broken there, if that's any help.
On 16/09/2020 23:50, Adrian Chadd wrote:
> Hi!
>
> Dang, ok. Well, rtwn was broken on freebsd-head due to changes elsewhere so we need to get those fixed before we can see
> what's up with it.
>
> I'll post updates to freebsd-wireless if/when I figure it out. :P
>
>
>
>
> -adrian
>
>
> On Wed, 16 Sep 2020 at 15:43, James Wright <james.wright at digital-chaos.com <mailto:james.wright at digital-chaos.com>> wrote:
>
> On 16/09/2020 22:36, Adrian Chadd wrote:
> >
> >
> > On Wed, 16 Sep 2020 at 13:41, James Wright <james.wright at digital-chaos.com
> <mailto:james.wright at digital-chaos.com> <mailto:james.wright at digital-chaos.com
> <mailto:james.wright at digital-chaos.com>>> 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
> <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%[ ] 8.87M 806KB/s eta 81m 35s
>
>
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