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From: Paul Rubin <no.email@nospam.invalid>
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Subject: Re: Forth dictionary implementation and performance
Date: Sun, 31 Jan 2016 11:57:50 -0800
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anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
> Note MAP_PRIVATE; from the documentation: "Updates to the mapping are
> not visible to other processes mapping the same file, and are not
> carried through to the underlying file." 

Hmm, I remember noticing that, but it didn't seem to displace the part
saying opening the file for read/write was required for PROT_WRITE.  I
asked on #linux IRC and someone there said it was undefined behaviour
under POSIX, so I'd be scared to deploy it in anything serious, but
anyway it seems to work for the example.

> in other words, mmap() is used here as (a hopefully more efficient
> variant of) read().

Yes, that part made sense.  Though reading the file in a single read()
call might conceivably be faster than mmap'ing the file and taking
multiple page faults while traversing it.  I think the next thing after
that is to use AIO to know which pages are available at a given time.
For such a small file I doubt any of this makes any difference, though.