linux-kernel - Re: kernel page table mapping for >1GB <3 GB for x86 arch without PAE

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Message-ID: <8980.20135.qm@web45211.mail.sp1.yahoo.com>
Date:	Fri, 28 Aug 2009 12:44:25 -0700 (PDT)
From:	joe Shmoe <jsmoe3@...oo.com>
To:	Valdis.Kletnieks@...edu
Cc:	linux-kernel@...r.kernel.org
Subject: Re: kernel page table mapping for >1GB <3 GB for x86 arch without PAE

No I am not talking about embedded systems. It is just an example.
My question is what is preventing the kernel from setting up the page tables so that entire RAM can be mapped upto 4 GB.

page tables have to be setup for every process anyway with first 768 PDE entries being unique and remaining 256 entries being same for all the processes.


--- On Fri, 8/28/09, Valdis.Kletnieks@...edu <Valdis.Kletnieks@...edu> wrote:

> From: Valdis.Kletnieks@...edu <Valdis.Kletnieks@...edu>
> Subject: Re: kernel page table mapping for >1GB <3 GB for x86 arch without PAE
> To: "joe Shmoe" <jsmoe3@...oo.com>
> Cc: "Roland Dreier" <rdreier@...co.com>, linux-kernel@...r.kernel.org
> Date: Friday, August 28, 2009, 3:13 PM
> On Fri, 28 Aug 2009 11:40:56 PDT, joe
> Shmoe said:
> 
> > For the sake of discussion, let us say I have 3.5 GB
> of RAM of x86 with PAE
> > disabled and I have only one process running other
> than kernel.
> 
> Oh, so an embedded environment. Sure, you could play games
> with that.
> 
> But most Linux systems have more processes running than
> just 'init'. And
> in that case, what do you do with your memory map?  It
> gets a bit more
> complicated then....
> 
> 


      
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