mmap changes, mostly for aout right now

Ken Raeburn
Wed Nov 8 12:47:00 GMT 1995

The file is never going to be written at the same time as mmap is
used, at least not in situations where I'd care about the results.
(If you're rewriting the input files while the linker is reading them,
you lose.)  But the file may get written by the assembler just before
it gets mapped by the linker.  Is it likely to lose in that case?  I'm
not very familiar with buffer-cache/VM interactions.

Autoconf already has one test for a known failure mode of mmap.  Can
you extend it to detect the NetBSD problems?  Would it only show up
with NFS?

I'm going to add some code so that the mmap code can be enabled or
disabled by configure options.  I want to get a release out soon, and
while the mmap code does seem to improve performance in most cases
I've tried, it's not worth risking serious instability.  It would be
nice to make it the default someday if I can get more performance out
of it, but that'll require more time and testing.

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