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Date: Thu, 20 Jun 2002 16:50:26 +0200 (CEST)
From: Jirka Kosina <jikos@jikos.cz>
To: Brian Gerst <bgerst@didntduck.org>
cc: devnull@adc.idt.com, <linux-kernel@vger.kernel.org>
Subject: Re: >3G Memory support
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On Thu, 20 Jun 2002, Brian Gerst wrote:

> > What limits user space to 3GB.
> Hardware limitations imposed by the x86 architecture.  The x86 only has 
> _one_ virtual address space, which has to be shared by user space and 
> kernel space.  It is not possible to give user space more virtual 
> address space without taking it away from the kernel.

You can theoretically run kernel in one task (I mean "task" in the 
Intel-processor-meaning of the word ;) ) and userspace programs in another 
task, which will result in having 4GB of memory for both of them, won't 
it?

I know, there would be big compilcations - for example copying data 
betweeen userspace and kernelspace should be problem, and if implemented, 
I can't imagine how to do it considerably fast...which is IMHO the main 
reason why it isn't done such way.

-- 
JiKos.


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