Subject: Re: Cygwinb19.dll
From: [email-masked] (Benjamin Riefenstahl)

26 Jun 1998 22:12:04 -0700
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To: "[email-masked]'" <[email-masked]>

Hi Ed,

Edward Avis wrote:
> AFAIK, Windows loads a _separate copy_ of each DLL for every program
> that uses it.  That's one of the reasons it uses so much memory.
>
> (Please tell me I'm wrong... :-( )

You're wrong ;-)

Windows creates the *illusion* of loading "a separate copy of each DLL
for every program." Actually DLLs are just memory mapped copy-on-write.
The "memory mapping" part means that executable code does not go into
the swap files and that all programs can use the same memory for a
common DLL, and the "copy-on-write" part means that if for some
reasoncode pages need to be changed after loading (e.g. a debugger
setting breakpounts, or relocations taking place) the affected pages
will still be duplicated for this process and possibly copied to
separate pages in the swap.

so long, benny
======================================
Benjamin Riefenstahl ([email-masked])
Crocodial Communications EntwicklungsGmbH
Ruhrstraße 61, D-22761 Hamburg, Germany
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