[RFC PATCH v2 05/11] mm: thp: Correct the HPAGE_PMD_ORDER check.

Steve Capper steve.capper at linaro.org
Wed May 8 08:03:08 EDT 2013

On Wed, May 08, 2013 at 03:44:17PM +0300, Kirill A. Shutemov wrote:
> On Wed, May 08, 2013 at 10:52:37AM +0100, Steve Capper wrote:
> > All Transparent Huge Pages are allocated by the buddy allocator.
> > 
> > A compile time check is in place that fails when the order of a
> > transparent huge page is too large to be allocated by the buddy
> > allocator. Unfortunately that compile time check passes when:
> > ( which is incorrect as the buddy allocator can only allocate
> > memory of order strictly less than MAX_ORDER. )
> It looks confusing to me. Shouldn't we fix what MAX_ORDER means instead?

It confused me as I originally had 13 as the order and couldn't
allocate any 512MB THPs :-).

MAX_ORDER appears to be used quite a lot so I think it would be
safer to change the use case here rather than its meaning.


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