Re: [PATCH 3/4] mm/hugetlb: make hugetlb migration callback CMA aware

[Vlastimil Babka]

On 7/15/20 7:05 AM, js1304@xxxxxxxxx wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> 
> new_non_cma_page() in gup.c requires to allocate the new page that is not
> on the CMA area. new_non_cma_page() implements it by using allocation
> scope APIs.
> 
> However, there is a work-around for hugetlb. Normal hugetlb page
> allocation API for migration is alloc_huge_page_nodemask(). It consists
> of two steps. First is dequeing from the pool. Second is, if there is no
> available page on the queue, allocating by using the page allocator.
> 
> new_non_cma_page() can't use this API since first step (deque) isn't
> aware of scope API to exclude CMA area. So, new_non_cma_page() exports
> hugetlb internal function for the second step, alloc_migrate_huge_page(),
> to global scope and uses it directly. This is suboptimal since hugetlb
> pages on the queue cannot be utilized.
> 
> This patch tries to fix this situation by making the deque function on
> hugetlb CMA aware. In the deque function, CMA memory is skipped if
> PF_MEMALLOC_NOCMA flag is found.
> 
> Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>