rt61pci - bad performance

From: Andreas
Date: Sun Aug 08 2010 - 05:55:38 EST


Hello!

I've got the following hardware


01:05.0 Network controller: RaLink RT2561/RT61 rev B 802.11g
Subsystem: Micro-Star International Co., Ltd. Device b833
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Latency: 128, Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ 21
Region 0: Memory at cc000000 (32-bit, non-prefetchable) [size=32K]
Capabilities: [40] Power Management version 2
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
Kernel driver in use: ndiswrapper


running on a 32bit notebook with kernel 2.6.34-12-desktop (OpenSuSE 11.3). There is no difference between the compat-wireless-modules 2010-07-20 and the original modules shipped with the openSuSE 11.3 kernel.

If the rt61-chip is connected to a AP using rt61pci, the best throughput, which can be achieved (at the same place), is about 1,7 MBytes/s.

kernel: [ 656.112190] cfg80211: Calling CRDA to update world regulatory domain
kernel: [ 656.112267] cfg80211: Calling CRDA for country: DE
kernel: [ 656.169518] cfg80211: Regulatory domain changed to country: DE
kernel: [ 656.169524] (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
kernel: [ 656.169528] (2400000 KHz - 2483500 KHz @ 40000 KHz), (N/A, 2000 mBm)
kernel: [ 656.169532] (5150000 KHz - 5350000 KHz @ 40000 KHz), (N/A, 2000 mBm)
kernel: [ 656.169535] (5470000 KHz - 5725000 KHz @ 40000 KHz), (N/A, 2698 mBm)
kernel: [ 656.206228] rt61pci 0000:01:05.0: PCI INT A -> GSI 21 (level, low) -> IRQ 21
kernel: [ 656.219941] phy0: Selected rate control algorithm 'minstrel'
kernel: [ 656.222216] Registered led device: rt61pci-phy0::radio
kernel: [ 656.222658] Registered led device: rt61pci-phy0::assoc
kernel: notebook1 ifup: wlan0 device: RaLink RT2561/RT61 rev B 802.11g



wlan0 IEEE 802.11bg ESSID:"--------"
Mode:Managed Frequency:2.412 GHz Access Point: some AP
Bit Rate=1 Mb/s Tx-Power=5 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=38/70 Signal level=-72 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

The throughput is measured with ping -f -s 7000 and xosview -n.




If I'm using ndiswrapper with the windows driver, first of all, I can see additional information in iwconfig:

wlan0 IEEE 802.11g ESSID:"--------"
Mode:Managed Frequency:2.412 GHz Access Point: some AP
Bit Rate=54 Mb/s Tx-Power:20 dBm Sensitivity=-121 dBm
RTS thr=2347 B Fragment thr=2346 B
Encryption key:some key Security mode:restricted
Power Management:off
Link Quality:62/100 Signal level:-56 dBm Noise level:-96 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0


There is a switch for sensitivity (which is not supported with rt61pci) and the link quality compared with ndiswrapper is worse (38% to 62%).

The following is remarkably too:
ndiswrapper uses a Tx-Power of 20 dBm, rt61pci only 5 dBm. I don't know, why rt61pci uses 5 dBm. It's a hard limit and I can't set it on a value higher than 5 unless the driver is patched. Nevertheless, setting a higher value (of 20 dBm) by patch does not mean to get a better performance.
Ndiswrapper shows an encryption key, rt61pci not. Does it mean, that rt61pci doesn't use hardware encryption?


With ndiswrapper, the rt61pci-chip achieves a throughput of 2,6 MBytes/s - that's about 1 MByte/s more than rt61pci.

I have to say, that the difference between rt61pci and ndiswrapper gets worse if the link quality is getting more badly. Or in other words: ndiswrapper handles bad connections better then rt61pci.


Do you have any idea to get rt61pci working as fast as ndiswrapper?


Kind regards,
Andreas
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