[Lhms-devel] Re: Help text for memory model config section?

Dave Hansen haveblue at us.ibm.com
Fri Jul 8 01:12:31 EST 2005

On Thu, 2005-07-07 at 10:40 +1000, Anton Blanchard wrote:
> > I think someone once told me that LMB size is 'adjusted' based on the
> > amount of memory in the system?  The more memory, the bigger the LMBs.
> > But, it was possible to have LMBs as small as 16MB.  Does that sound
> > correct?
> > 
> > As a data point, my OpenPower 720 with 8GB of memory has 32MB LMBs.
> Definitely, we would expect the big memory layouts to have 256MB LMBs.
> However it looks like sparsemem uses compile time constants to work out
> the layout of the structures.

It does, but the root reason for this is that we encode the section
number into the page->flags, which are statically allocated.

However, we could probably include a global, variable section shift to
globally increase the section size.  But, I don't think it's really
worth the complexity.

The ia64 folks require a two-level table instead of a flat array, and I
think we'll just do that for ppc64 as well.

-- Dave

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