mmap's seg_size reconfigurable, working with NFS? extentions?

[Inst.f.Prakt.Info 1802]

I have some questions about the current state of mmap features on apollo,
SUN etc. From the manual I see:

1.) The segment size seems to be fixed (32K on apollo SR10). There is not
even a macro in <sys/mmap.h>. Is there a portable way to get the system's
seg_size. (workaround: Search for a correct adress boundary
by MMAPping to a fixed address. Might be portable)

2.) Can one (easily, portably) reconfigure the systems's seg_size??

3.) man mmap says that only ordinary files (not NFS) can be mapped.
On apollo you can mmap also to different nodes within the ring by
giving the full name (e.g. //other_disknode/myfile).
Is there a way to mmap to different nodes in other systems?

4.) There might be some changes/extentions of mmap features in future.
(says man mmap) Does anybody know something more about that?

Thanks Ulrich
(Ulrich Neumerkel  ulrich at vip.at  <-- for personal replies )