Re: 2nd attemt at reviving the filesystem limit discussion.

[Marcus Brinkmann]

On Fri, Dec 06, 2002 at 11:05:13AM +0100, M. Gerards wrote:
> Another thing I wonder: Why do memory 
> objects have a maximum size of 4GB? Isn't it possible to create a memory 
> object 
> with the size of the entire store and use mapping windows? (Or am I confused 
> again? :)). Can someone please describe how this works in more detail if I'm 
> wrong? I assume more people are confused by this.

The reason for the limit is because the address space on IA32 architecture
is 32 bit.  Now, you _could_ of course change the kernel interfaces to allow
for larger memory objects and only limit mapping windows to 4gb.  This might
be a nice strategy to solve the atomicity issue.  OTOH, that would mean to
make the kernel more complex, which is the opposite of the general trend we
try to follow (ie, L4 is even closer to the hardware than Mach).

Thanks,
Marcus

-- 
`Rhubarb is no Egyptian god.' GNU      http://www.gnu.org    marcus@gnu.org
Marcus Brinkmann              The Hurd http://www.gnu.org/software/hurd/
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de/