🚀 go-pugleaf

In article <5180@crdgw1.crd.ge.com> hammondr@sunroof.crd.ge.com (Richard A Hammond) writes:
> Everybody seems to be missing the crucial fact about memory mapped files!

> They ONLY work for cases where the file size is < virtual address space!!!

Why? Nobody said you had to map the file in from the beginning. Even on a
PDP-11, there's no problem with seeking to location 2^20 and starting the
mapping from there (or using whatever mechanism you want).

Nobody is denying that both techniques have advantages in certain domains: for
example, it's hard to memory map a serial port. But this isn't one of them.

> If I recall properly, Multics hardware couldn't address more than 2^18
> words(?) per segment.  While that was huge at the time, it isn't all
> that interesting now as an upper limit.  What, if anything, did the
> programmer do to handle files > 1 segment in length?

They used multisegment files, which was probably a pain.

> This is not to say that memory mapped files are a "BAD IDEA", just
> that they have limits that must be considered by the programmer.

As do stream files.
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 _--_|\  Peter da Silva. +1 713 274 5180. <peter@ficc.uu.net>.
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