I am porting linux kernel 2.6.19 on a platform based on PPC750FX together 
with a Marvell GT64260.
I use a patched 643xx driver which is back ported to 64260 by Steven J. 
Hill.
I have ethernet now up and running, but only if I switch debug on, which 
generates a big bunch of screen messages.
As soon as I switch debug off, I get the message "Virtual device %s asks 
to queue packet!" on every transmission request.

This happens on ping an other system.

Has anyone experience in such an event? Is there anything how I can speed 
up performance with the 64260?
Is there a similar problem known with the 64360?

No, this does not happen on the mv64360.  As I recall, that message occurs
when something attempts to queue a packet to a driver that has called
netif_stop_queue() but hasn't yet called netif_wake_queue().  I would
guess that when you turn debug on, you are changing the driver logic
in addition to the timing.

-Dale