Pre-Allocate tablespace on disk

Hello,

I was wondering if there is a way to pre-allocate tablespace on disk before adding data and indexes.
My understanding is:
PG writes data into files sequentially. If more space is needed, disk space is requested from the OS and if there is
space,the OS will give PG a file system block and PG will write data/indexes until that block is full and so on. 
Other database that I have worked with before and that I'm still working with, allow you to pre-allocate disk space so
youget huge chunks of contiguous space at one, which has major impacts on database performance. 

Can this be done with PG at all? If not, is this planned for any time in the future?

best regards,
chris
--
chris ruprecht
database grunt and bit pusher extraordinaíre 