I suppose that an app that needs mmap but not MAP_FIXED (which is
allowed by POSIX sans XSI) could write its own special-purpose
Autoconf macro for that. That being said, if you're planning to use
mmap on AIX good luck; you may need it[5].
The complaints seem to primarily be about archaic systems.
GraphicsMagick optionally uses mmap() for some use cases, where there is
substantial benefit. There have not been any complaints about it,
including under IBM's AIX. At one time (long ago) I noticed that Linux
was the worst performer out of the then current OSs when using mmap()
for file I/O. Behavior is subject to change.
Regardless, using mmap() for file I/O is no magic bullet. It transfers
all control to the OS, and the hardware. The program may be
de-scheduled (waiting for page-in, or even page-out) when it could
otherwise be doing something useful.
Bob
--
Bob Friesenhahn
bfriesen@xxxxxxxxxxxxxxxxxxx, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
Public Key, http://www.simplesystems.org/users/bfriesen/public-key.txt
