To large page or not to large page

[Benjamin Herrenschmidt]

On Fri, 2005-09-30 at 20:43 -0400, Jimi Xenidis wrote:
> It seems as tho Linux will map the kernel with large pages if the
> processor allows it regardless if the lmb is sufficient to hold a
> large page, correct?
> 
> Is there some runtime option to force the use of 4K pages.
> 
> Ultimately, my desire is to define a 256Mig segment that, using a
> Hypervisor, that can be populated by shared pages that can physically
> belong to the  hypervisor or other partions/domains) and restrict the
> mappings to 4k.  I have some ideas, but am willing to hear any suggestions.

Does that segment has to be part of the linear mapping ? Can't it just
be mapped afterward using a kernel virtual mapping ? Also, don't forget
that the 64k pages patch won't support 4k pages at all for performances
reasons when CONFIG_PPC_64K_PAGES is enabled (at least on processors
that have HW support for 64k pages) .

Ben?