Define Linux system memory

[Clint Thomas]

 Yes, in my particular case I have 256MB of ram and want to cut off
about 16MB, so I passed it the argument mem=0x0EFFFFFF. I also tried
mem=240M, but it does not seem to work correctly. Whenever I pass it
those two options, Linux believes it has 191820K of memory, about 64MB
instead of the 16MB.

When I pass it a mem= argument that is lower than the 191820K, such as
mem=180M, the number decreases again, down to around 142M. Is there any
reason that Linux is allocating in huge blocks like that? Can I not be
so specific as to say the exact number of bytes I want Linux to see?

-----Original Message-----
From: Frank [mailto:frannk_m1 at yahoo.com] 
Sent: Wednesday, December 20, 2006 11:57 AM
To: Clint Thomas; linuxppc-embedded at ozlabs.org
Subject: Re: Define Linux system memory


--- Clint Thomas <cthomas at Soneticom.com> wrote:

> To anybody who has done this before or understands how to do this, I 
> was wondering if you know how to "tell" the kernel how much memory 
> there is in the system. An example would be if I have 512MB of RAM, 
> but only want the system to know that there is about 500MB in RAM, so 
> that 12MB does not exist to the OS/kernel. Would this require mucking 
> about in U-boot?
> or can I just define this in the kernel source? Thanks
>  
> Clinton Thomas
On the kernel command line passed by u-boot:
mem=500M

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