Hi, all

I'm looking through the uvm code in 3.6, and ran across a puzzling
comment -

near uvm_map.c:2108
/*
* uvm_map_submap: punch down part of a map into a submap
*
* => only the kernel_map is allowed to be submapped
* => the purpose of submapping is to break up the locking granularity
* of a larger map

My question is, why is the creation of submaps limited to only the
kernel? (Neither the tech archives nor cranor's thesis answers this
question so ...)

Secondly, what would it take to get the submap functionality working for
userland? Are there any specific "gotcha"'s that I need to be aware of
for getting the submap stuff working in userland?

Thanks,

-Jason Kim.