port forwarding really really slow

[GeorgeM]

i'm using dropbear for dynamic port forwarding. i've noticed that if i 
instruct the socks clients to do dns lookups via tunnel the connection 
becomes unusably slow. for example trying to open youtube, or other reasonably
complex site will timeout during page load. my question is: does dropbear 
do dns lookups asynchroneously? does it cache recent queries? is there
an option i've missed out?