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void *
     mmap(void * addr, size_t len, int prot, int flags, int fd, off_t offset)

BUGS
     len is limited to 2GB.  Mmapping slightly more than 2GB doesn't work, but
     it is possible to map a window of size (filesize % 2GB) for file sizes of
     slightly less than 2G, 4GB, 6GB and 8GB.

     The limit is imposed for a variety of reasons. Most of them have to do
     with FreeBSD not wanting to use 64 bit offsets in the VM system due to
     the extreme performance penalty. So FreeBSD uses 32bit page indexes and
     this gives FreeBSD a maximum of 8TB filesizes. It's actually bugs in the
     filesystem code that causes the limit to be further restricted to 1TB
     (loss of precision when doing blockno calculations).

     Another reason for the 2GB limit is that filesystem metadata can reside
     at negative offsets.

     We currently can only deal with page aligned file offsets.


-- 
Ian Freislich
UUNET S.A. (Pty) Ltd