Re: rate instability in wireless stack

[Andi Kleen <andi@firstfloor.org>]

On Mon, Jan 05, 2009 at 03:41:58PM +0100, Felix Fietkau wrote:
> Andi Kleen wrote:
> > With Larry's patch reverted. Rate is still at 1Mbit/s of course.
> > This is all only with rtl8180, I didn't try everything on the realtek
> > card too. 
> > 
> > -Andi
> > 
> > rate     throughput  ewma prob   this prob  this succ/attempt   success    attempts
> > TtP  1         0.9       99.2      100.0          1(  1)         23          32
> >      2         0.0        0.0        0.0          0(  0)          0           0
> >      5.5       0.0        0.0        0.0          0(  0)          0           1
> >     11         0.0        0.0        0.0          0(  0)          0           0
> >      6         0.0        0.0        0.0          0(  0)          0           0
> >      9         0.0        0.0        0.0          0(  0)          0           0
> >     12         0.0        0.0        0.0          0(  0)          0           0
> >     18         0.0        0.0        0.0          0(  0)          0           0
> >     24         0.0        0.0        0.0          0(  0)          0           0
> >     36         0.0        0.0        0.0          0(  0)          0           0
> >     48         0.0        0.0        0.0          0(  0)          0           0
> >     54         0.0        0.0        0.0          0(  0)          0           0
> > 
> > Total packet count::    ideal 25      lookaround 1
> OK, that confirms that Larry's patch was wrong - at least the dump
> looks consistent now.
> Probably the RT2561 and the RTL8180 simply have a lower Tx power and

> thus can't get the signal through the walls as easily as the zd1211rw.

That surprises me because I use a real antenna on them which the zd1211rw
is just itself. Also some laptops with Intel wireless have no trouble
talking through the walls at full rate when I put them on the same position.

Hmm perhaps I should try to find a Windows box and see if it works
there. That would rule out hardware issues.

> If you still think that it's a rate control problem, please try all

I don't know what it is, i just know that it doesn't work and
from the evidence I gathered so far it looks like a Linux software
problem.

> the rates individually and see if one of them works better.

Forcing the rates works somewhat, but the link quality is very poor
(10-15/100) and fluctuates.

-Andi

-- 
ak@linux.intel.com