[Soekris] Atheros maxes out CPU at 24Mb/s on net4801

[Frank Cole]

Please post your soekris comBIOS version and kernel config.  This doesnt 
sound like a madwifi driver problem, it sound more like a kernel tuning 
issue.

Frank

Sam Leffler wrote:
> Flemming Frandsen wrote:
>> Hi, I'm using Atheros 5212 minipci cards with the latest linux driver 
>> (from SVN) and I find that I cannot get more than 24Mb/s out of the 
>> wireless link, is that normal?
> 
> Did you ask on the madwifi lists?  I routinely get 28 Mb/s for upstream 
> tcp netperf w/ bursting enabled.  Unidirectional udp tests usually get 
> 36 Mb/s.  All numbers are open air w/ strong signal.  freebsd, not linux.
> 
>> I've tested it by routing traffic through the link and running iperf on 
>> separate machines, so nothing runs on the net4801 machines other than 
>> the kernel and top.
>>
>> I first tried setting one box to AP and the other to Sta and that got me 
>> 13Mb/s with the CPU maxed out, when I switched to ahdemo mode (like 
>> adhoc, but without any fancy stuff like mac addresses) that got me 22Mb/s.
>>
>> Then I upgraded to the very latest driver and that got me 24Mb/s, but 
>> the CPU is still the bottleneck, which is really quite sad as I was 
>> hoping to saturate the wireless link.
>>
>> One could argue that I'm simply trying to go faster than the cpu allows, 
>> but I get 50Mb/s if I iperf to the box from eth0, so the CPU should be 
>> capable of routing that much, right?
>>
>> I guess my main questions are:
>> * Is this really all I can hope for with Atheros cards?
>> * If it's the card that has been designed to eat CPU then are there
>>    others that do more work in hardware?
>> * On paper the net5501 looks to be about twice as fast as net4801,
>>    which is not quite enough to reach the performance I want, how does
>>    the net5501 CPU perform compared to net4801?
>>
>>
>> Max at 54Mb/s (CPU maxed out):
>>    AP/STA mode: 13Mb/s
>>    ahdemo mode: 22Mb/s
>>    New driver:  24Mb/s
>>
>> 802.11a (ch 136):
>>    Bit Rate=54 Mb/s : 24.3Mb/s (0% idle)
>>    Bit Rate=36 Mb/s : 16Mb/s (15% idle)
>>    Bit Rate=24 Mb/s : 15Mb/s (37% idle)
>>    Bit Rate=6 Mb/s  : 4.3Mb/s (81% idle)
>>
>> 802.11Ta (ch 152):
>>    Bit Rate=54 Mb/s : 23.5Mb/s
>>    Bit Rate=36 Mb/s : 23.5Mb/s
>>    Bit Rate=24 Mb/s : 23.9Mb/s
>>    Bit Rate=12 Mb/s : 17Mb/s
>>    Bit Rate=6 Mb/s  : 9Mb/s
>>
>> The driver version is:
>> ath_hal: 0.9.30.13 (AR5210, AR5211, AR5212, AR5416, RF5111, RF5112, 
>> RF2413, RF54
>> 13, RF2133)
>> wlan: 0.8.4.2 (svn r2377)
>> ath_pci: 0.9.4.5 (svn r2377)
>> ath_rate_sample: 1.2 (svn r2377)
>>
> 
> You need to ask the madwifi folks for help.  I recently had an exchange 
> w/ a developer who was trying to reduce cpu overhead but a 4801 should 
> be able to easily saturate the wireless link.
> 
> 	Sam
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> Soekris-tech mailing list
> Soekris-tech at lists.soekris.com
> http://lists.soekris.com/mailman/listinfo/soekris-tech
> 
> 

-- 
Frank R Cole jr
President/CEO
Cole Innovations, Inc.

Ph: (315) 533-1336
Fx: (315) 533-1253

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