vector write/read

[Alan Bateman]

Florian Weimer wrote:
> :
> On recent Linux, it should be possible to fake the read case using
> posix_fadvise and pread (the interesting property is reordering among
> multiple reads).  For the write case, pwrite can be used directly
> because there's no implied ordering constraint.
>
> (It's unlikely that the savings due to reduced syscall overhead are
> actually relevant on Linux.)
>   
It is likely we would need to emulate this on other operating systems 
aswell. In any case, this is an area that needs more consideration as 
it's a bit niche and may not be used by many applications.

-Alan.