Subject: Re: The question about the high memory support on MPC8360?

From: Scott Wood <[email-masked]>
Date: Wed, 28 Nov 2007 10:57:38 -0600

vijay baskar wrote:
> Hi, "The kernel also allows hardcoded mapping of IO regions into its 
> virtual address space through the io_block_mapping interface."
> 
> Can u tell me how this is in current arch/powerpc.

Everything is explicitly ioremapped.

> Also does it mean that whatever be the size of the ram > 768 MB there
>  is not going to be much improvement in performance in kernel space 
> irrespective of invoking CONFIG_HIGHMEM or not?

Well, the kernel can use highmem for cache...  I'm not sure what you
mean by "in kernel space".

> Also do you think this low mem be enough if i have lots of kernel 
> space processes each invoking lots of kmallocs.

That depends on what you mean by "lots". :-)

You'll have 768MB of lowmem, and kmallocs can only use lowmem.

> Will there be bottle necks?? Also what alternative do we have if  low
> mem of 768 MB is not enough??

You'll need to change the user/kernel split, and deal with anything that 
breaks in the process.

Or get a 64-bit chip. :-)

-Scott