Slow Wifi... getting closer

Dave Kroetsch dave at
Fri Feb 27 12:39:59 EST 2009

Hey all,

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.

To decouple the printk's from the scheduling problem, I've set up the 
driver to blink an LED each time it enters the lbs_main thread.  So, I 
begin a transfer, and see lots of blinking activity.  When I start the 
UDP test this grinds to a halt - indicating that the thread is not being 
scheduled as often as it should.

Anyone got any suggestions on what can be done to make sure this thread 
gets scheduled with higher priority?  Trying a sched_setscheduler causes 
an Oops, and I don't have any RT patches installed to play with that stuff.


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