Re: reg adjust_total_lowmem

On Fri, Oct 26, 2007 at 10:04:19AM -0500, Kumar Gala wrote:

On Oct 25, 2007, at 10:51 PM, Surya Ravikiran wrote:

quoted

Hi,

I am trying to bootup a Linux kernel, on a FS eval board with 256M.
I pass the kernel argument mem=252M, and see that the kernel boots up
fine, but with much less memory, ~192M (the closes 64M multiple), and
I browsed through the code to see that the adjust_total_lowmem
function does not add up the residual memory to the total memory.
I am trying to understand why I cannot do this reserving of higher end
of the RAM during boot up,
I would appreciate your comments.

The reason you have 192M is that lowmem is the total amount of memory  
that can be covered by up to three CAM entries.  In the case of  
setting mem=252M that max that three CAM entries can cover is 192M (64 
+64+64).  You should be able to access the other 60M via HIGHMEM.

Why doesn't it just use a 256M mapping, and not access the last 4M?

-Scott