[openbeos] Re: mmap, vm2 and you

  • From: cdegea@xxxxxxxxxxxxxxxx (Cedric Degea)
  • To: openbeos@xxxxxxxxxxxxx
  • Date: Fri, 06 Sep 2002 18:10:35 CEST

Rudy Gingles <rudyatek@xxxxxxxxxxxxxx> wrote:
> >Anyway. What I wanted to ask you all is this - does anyone know of
> >MAP_COPY or MAP_PRIVATE being used in real software? I can write

> I always saw mmap as private, until it was specifically shared, in 
> which case you are correct about keeping all changes in real-time.
> As far as MAP_COPY, the only big usage that comes to mind is POSIX 
> and fork(). But even elsewhere, technically, there could be many 
> cases where you pass a buffer to another app, and use MAP_COPY rather 
> than specifically making a copy yourself. Just an idea.

Kernel newbie question: what will the kernelland counterpart
to userland mmap() be called? (the BeOS current map_memory()
call used by accelerant's drivers I mean).

At any rate, that one will definitely need the "straight forward"
version of mapping, in the context of accelerants (ie in the context
of mapping "memory" to memory), no funky copy-on-write feature there.

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