Re: [RFC PATCH 3/3] mm/map_contig: Add mmap(MAP_CONTIG) support

[Christopher Lameter]

On Thu, 12 Oct 2017, Anshuman Khandual wrote:

> > +static long __alloc_vma_contig_range(struct vm_area_struct *vma)
> > +{
> > +	gfp_t gfp = GFP_HIGHUSER | __GFP_ZERO;
>
> Would it be GFP_HIGHUSER_MOVABLE instead ? Why __GFP_ZERO ? If its
> coming from Buddy, every thing should have already been zeroed out
> in there. Am I missing something ?

Contiguous pages cannot and should not be moved. They will no longer be
contiguous then. Also the page migration code cannot handle this case.