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From: "Albert D. Cahalan" <acahalan@cs.uml.edu>
Message-Id: <200110250404.f9P44KM162546@saturn.cs.uml.edu>
Subject: Re: Allocating more than 890MB in the kernel?
To: ttabi@interactivesi.com (Timur Tabi)
Date: Thu, 25 Oct 2001 00:04:20 -0400 (EDT)
Cc: hpa@zytor.com (H. Peter Anvin), linux-kernel@vger.kernel.org
In-Reply-To: <3BD08B57.1070604@interactivesi.com> from "Timur Tabi" at Oct 19, 2001 03:21:43 PM
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> I need to allocate about 3/4 of available memory in the kernel. 
> If I had 2GB of RAM, I'd need to allocate 1.5GB.  If I had 8 GB
> of RAM, I'd need to allocate 6GB.  I just used 3GB/4GB because
> it's our current test platform.

The best you can do, IMHO:

1. reserve a 3 GB chunk of memory at boot
2. create a regular user process
3. have that process make a system call which will never return
4. in that system call, wipe out all memory mappings in the process
5. hand-craft a 3 GB memory mapping (0 GB virt --> 1 GB phys)
6. call your desired code, remembering to schedule by hand


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