>I once wanted to build something like dd but that overlapped reads and
>writes.  I ended up making it mmap MAP_ANON memory before forking into
>a reader process and a writer process; they transferred ownership of
>large blocks of memory by sending tiny tokens through a pipe.  It

if we set the bits on the anon page(s) to mske it resident, will it ever 
be sent to the unified cache(buffer cache originally) or will there be any 
overhead at all associated with I/O to that page?

This is assuming that the block of memory is used only for inter-process 
communication, but the data in memory is not to be saved to ufs.

thanks
-kamal