Slow Wifi... getting closer

[Daniel Mack]

On Fri, Feb 27, 2009 at 12:39:59PM -0500, Dave Kroetsch wrote:
> Ok, so I'm getting much closer to the root of this wifi slow down with 
> local UDP traffic.  I've tried putting printk's in the lbs_thread to see 
> how often it was being called, but this alone slows down traffic 
> dramatically.  My theory is that this is due to the fact that the printk 
> hands the task of printing and logging this message to another kernel 
> thread and this, therefore, mucks up the thread scheduling of the 
> lbs_main thread, resulting in slow transfers.

Just a general note in the hope be helpful: for debugging such fast path
code I found it handy to simply use counters in the places you want to
trace and then use a timer and dump them once a second (and probably
reset them). printk() happens to be expensive - especially on embedded
machines - and might also loose entries on message buffer overruns.

Daniel