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

[Flemming Frandsen]

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?

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)

-- 
  Regards Flemming Frandsen - YAPH - http://dion.swamp.dk