Re: ath0 / wlan0 on 8.0

On Thu, 2009-07-09 at 07:42 -0700, Sam Leffler wrote:
> Marten Vijn wrote:
> > hi all,
> >
> > When benchmarkmarking an ath0 card an I get these errors.
> > After a could (~10) no traffic is possible anymore.
> >  
>
> "no traffic is possible" doesn't say enough.  

Retested for beta-1
- ping does not respond any more.
- the client loses associations.

see: http://www.youtube.com/watch?v=sfE-YskT7XM
for a screen cast


> Do you see beacons from the ap?

- I still see beacon frames


> Are interrupts being received on the ap? Are you out of
> resources like mbufs?

What are the command to produce this information?

> I have seen, for example, things like nightly
> cron scripts accidentally left to run and kill operation.

Not very likey, It an NET4826, just rebooted,
this very reproducable it 1 or 2 test runs.

To much traffic that leads to a dos. I am aware that I create a lot
of traffic. That's why it is benchmark.

I created a new report for 8.0.beta-1 on the site with more info:

http://bsd.wifisoft.org/trac/wiki/crash4 

all (UDP) traffic created on the clients and flows to the server (one
jail per client)  

> I know several groups using the Alix board in similar configs to run
> production ap's with >10 users but you will need to tune the system for
> best operation.

I had 50~60 users concurrent on ap's on ApacheCon Amsterdam in spring.
Ap's did fail every couple of hours/days. That workable for 10 ap's, but
not for > 100.

> Under extreme wireless network load the PCI bus becomes
> a bottleneck and causes the host to be unable to setup each beacon frame
> in real-time to satisfy NextTBTT requirements.
>  Look at how the SWBA mechanism works in the driver and the hw.ath.hal.sw_brt and
> hw.ath.hal.dma_brt tunables.

Could you give my pointers for documentation/stuff to read? (it will
take me some time to read and maybe understand it. my background not
technical)

> Otherwise stuck beacon conditions can be caused by the ap not getting
> access to the wireless medium due to it being busy.  You should sniff
> traffic around the time of a problem for clues.  There are also h/w
> registers you can observe (e.g. with athregs) to see how busy the medium
> is from the POV of the ap.  There have been chip bugs related to this
> condition but doing a reset should always restore operation.

> If this
> isn't happening should be able to diagnose what's going with the
> existing facilities (e.g. athdebug msgs).

nice! I will rebuild the nanobsd img's to use
/usr/src/tools/tools/ath/*

> Understand however that building a product ap is nontrivial and the FreeBSD ath driver can
> easily be optimized better for this purpose.

I am not building a product, I am using FreeBSD wifi / networking env
and as show case of working Opensource Software. IHMO the benchmarking
could help harden to wlan drivers and FreeBSD based accesspoints.

I expect to double the clients in the benchmark in the coming weeks.
Then I will do more testing. Please let know how I can support to create
usable (debug) output.

thanks for your reply,
Marten


>
>     Sam
>
--
http://martenvijn.nl                 Marten Vijn
http://martenvijn.nl/trac/wiki/soas  Sugar on a Stick
http://bsd.wifisoft.org/nek/         The Network Event Kit
http://har2009.org                   13th-16th August
http://opencommunitycamp.org         26th Jul - 2nd August

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