How much virtual memory can a user process grab on the 64-bit
architectures?  

I notice that /usr/sys/arch/amd64/include/vmparam.h's MAXDSIZ on amd64
is till 1Gig.  Is this just an oversight or do bad things happen when
it is raised to some higher value say 2^46 or something else more in
line with the amd64's page table limits?  The sparc64 version of
vmparam.h mentions hangs when one goes above the 32-bit cut-off, but
that comment may no longer apply, or may only apply to the sparc64
kernel.  Anyone know what is going on here?

-wolfgang