There is one extra copy that is not shown in this diagram (you don't write directly into my I/O buffer, you write into something that I copy into my system I/O buffer when you ask me to do a write()).

Not on win--I can't speak to *nix. There is no "I/O buffer" involved. And no "copying".

The point is: The file is already on disk! And it doesn't get read in to a physical pages of RAM until you attempt to access it. And it doesn't get written (anywhere) unless you write to it. All that has happened up to the point where you attempt to read or write to the mapped address space is that a few virtual-to-physical mapping tables have been set up.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
RIP PCW It is as I've been saying!(Audio until 20090817)

In reply to Re^6: PV limits on 64-bit perls? by BrowserUk
in thread PV limits on 64-bit perls? by BrowserUk

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