[openbeos] Re: mmap, vm2 and you

  • From: François Revol <revol@xxxxxxx>
  • To: openbeos@xxxxxxxxxxxxx
  • Date: Fri, 06 Sep 2002 18:18:57 +0200 (MEST)

En réponse à Cedric Degea <cdegea@xxxxxxxxxxxxxxxx>:

> 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.
> 

I think you mean map_physical_memory() ?
This should still be provided, and isn't really exactly the same
(even if QNX does what map_physical_memory() with mmap() and a special 
flag, but this is for userland stuff).

François.

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