linux-kernel - Re: rt61pci - bad performance

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Message-Id: <20100812161157.00d5377f.akpm@linux-foundation.org>
Date:	Thu, 12 Aug 2010 16:11:57 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andreas <andihartmann@...19freenet.de>
Cc:	linux-kernel@...r.kernel.org, Ivo van Doorn <IvDoorn@...il.com>,
	Gertjan van Wingerde <gwingerde@...il.com>,
	linux-wireless@...r.kernel.org
Subject: Re: rt61pci - bad performance

(cc's added)

On Sun, 08 Aug 2010 11:49:49 +0200
Andreas <andihartmann@...19freenet.de> wrote:

> 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?
> 

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