I will see whether I can bisect the kernel patches and see which one
was
the good one. I have to figure out a way to do that, but if I do it and
find out, I will keep you posted.
So I tried every patch against cfq-iosched.c since January 5th, 2011
(2.6.37 release date) and none of it made things work.
I also tried the only existing patch against blk-throttle.c and it also
did not make a difference.
Unless you have another hint on where to look for the fix, I'd consider
this thing done for now.
Regards
Dominik