Re: rate instability in wireless stack

[Andi Kleen <andi@firstfloor.org>]

On Mon, Jan 05, 2009 at 04:25:58PM +0100, Felix Fietkau wrote:
> > Forcing the rates works somewhat, but the link quality is very poor
> > (10-15/100) and fluctuates.
> Another possibility is that the tx power is fine, but the
> sensitivity of the card is crap, so the packets actually make it,

Ok, but I see the same thing with two different cards, with different
chipsets (RaLink and RealTek). You think they both have that problem?

> Even if both cards work fine on Windows, I wouldn't assume that this
> is an issue with mac80211. The information that was used to write
> these two drivers was derived from very poor vendor codebases and
> limited information in datasheets, so it's much more likely that
> simply the Baseband/RF tuning is far from optimal on both cards.

Ok I won't try then. Setting up Windows would be quite a lot of
effort and I would prefer to avoid it.

> Maybe we can see more if you provide some minstrel stats after
> you've pushed more traffic through the link - 25-50 packets is not
> nearly enough for getting an accurate view of how good the link is.
> Try to push through a few megabytes of data...

Here are the statistics after a few MB.

rate     throughput  ewma prob   this prob  this succ/attempt   success    attempts
TtP  1         0.9       97.9      100.0          1(  1)      19284       21249
     2         0.0        0.0        0.0          0(  0)          0         101
     5.5       0.0        0.0        0.0          0(  0)          0         104
    11         0.0        0.0        0.0          0(  0)        253         397
     6         0.0        0.0        0.0          0(  0)          0         103
     9         0.0        0.0        0.0          0(  0)          0         106
    12         0.0        0.0        0.0          0(  0)          0         107
    18         0.0        0.0        0.0          0(  0)          0         104
    24         0.0        0.0        0.0          0(  0)          0         111
    36         0.0        0.0        0.0          0(  0)          0         120
    48         0.0        0.0        0.0          0(  0)          0         179
    54         0.0        0.0        0.0          0(  0)          0         253

Total packet count::    ideal 9023      lookaround 474

-Andi
-- 
ak@linux.intel.com