Re: [PATCH v2 11/12] mm: migrate: move_pages() supports thp migration

[Kirill A. Shutemov]

On Tue, Nov 08, 2016 at 08:31:56AM +0900, Naoya Horiguchi wrote:
> This patch enables thp migration for move_pages(2).
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> ---
>  mm/migrate.c | 37 ++++++++++++++++++++++++++++---------
>  1 file changed, 28 insertions(+), 9 deletions(-)
> 
> diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/migrate.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/migrate.c
> index 97ab8d9..6a589b9 100644
> --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/migrate.c
> +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/migrate.c
> @@ -1443,7 +1443,17 @@ static struct page *new_page_node(struct page *p, unsigned long private,
>  	if (PageHuge(p))
>  		return alloc_huge_page_node(page_hstate(compound_head(p)),
>  					pm->node);
> -	else
> +	else if (thp_migration_supported() && PageTransHuge(p)) {
> +		struct page *thp;
> +
> +		thp = alloc_pages_node(pm->node,
> +			(GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM,
> +			HPAGE_PMD_ORDER);
> +		if (!thp)
> +			return NULL;
> +		prep_transhuge_page(thp);
> +		return thp;
> +	} else
>  		return __alloc_pages_node(pm->node,
>  				GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
>  }
> @@ -1470,6 +1480,8 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
>  	for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
>  		struct vm_area_struct *vma;
>  		struct page *page;
> +		struct page *head;
> +		unsigned int follflags;
>  
>  		err = -EFAULT;
>  		vma = find_vma(mm, pp->addr);
> @@ -1477,8 +1489,10 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
>  			goto set_status;
>  
>  		/* FOLL_DUMP to ignore special (like zero) pages */
> -		page = follow_page(vma, pp->addr,
> -				FOLL_GET | FOLL_SPLIT | FOLL_DUMP);
> +		follflags = FOLL_GET | FOLL_SPLIT | FOLL_DUMP;
> +		if (thp_migration_supported())
> +			follflags &= ~FOLL_SPLIT;

Nit: I would rather filp the condition -- adding flag is easier to read
than clearing.

> +		page = follow_page(vma, pp->addr, follflags);
>  
>  		err = PTR_ERR(page);
>  		if (IS_ERR(page))
> @@ -1488,7 +1502,6 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
>  		if (!page)
>  			goto set_status;
>  
> -		pp->page = page;
>  		err = page_to_nid(page);
>  
>  		if (err == pp->node)
> @@ -1503,16 +1516,22 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
>  			goto put_and_set;
>  
>  		if (PageHuge(page)) {
> -			if (PageHead(page))
> +			if (PageHead(page)) {
>  				isolate_huge_page(page, &pagelist);
> +				err = 0;
> +				pp->page = page;
> +			}
>  			goto put_and_set;
>  		}
>  
> -		err = isolate_lru_page(page);
> +		pp->page = compound_head(page);
> +		head = compound_head(page);
> +		err = isolate_lru_page(head);
>  		if (!err) {
> -			list_add_tail(&page->lru, &pagelist);
> -			inc_node_page_state(page, NR_ISOLATED_ANON +
> -					    page_is_file_cache(page));
> +			list_add_tail(&head->lru, &pagelist);
> +			mod_node_page_state(page_pgdat(head),
> +				NR_ISOLATED_ANON + page_is_file_cache(head),
> +				hpage_nr_pages(head));
>  		}
>  put_and_set:
>  		/*
> -- 
> 2.7.0
> 
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-- 
 Kirill A. Shutemov