Re: [PATCH 1/8] migrate: make core migration code aware of hugepage

[Hillf Danton <dhillf@gmail.com>]

Hey Naoya,

On Fri, Jul 19, 2013 at 5:34 AM, Naoya Horiguchi
<n-horiguchi@ah.jp.nec.com> wrote:
> Before enabling each user of page migration to support hugepage,
> this patch enables the list of pages for migration to link not only
> LRU pages, but also hugepages. As a result, putback_movable_pages()
> and migrate_pages() can handle both of LRU pages and hugepages.
>
> ChangeLog v3:
>  - revert introducing migrate_movable_pages
>  - add isolate_huge_page
>
> ChangeLog v2:
>  - move code removing VM_HUGETLB from vma_migratable check into a
>    separate patch
>  - hold hugetlb_lock in putback_active_hugepage
>  - update comment near the definition of hugetlb_lock
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> ---
>  include/linux/hugetlb.h |  6 ++++++
>  mm/hugetlb.c            | 32 +++++++++++++++++++++++++++++++-
>  mm/migrate.c            | 10 +++++++++-
>  3 files changed, 46 insertions(+), 2 deletions(-)
>
> diff --git v3.11-rc1.orig/include/linux/hugetlb.h v3.11-rc1/include/linux/hugetlb.h
> index c2b1801..0b7a9e7 100644
> --- v3.11-rc1.orig/include/linux/hugetlb.h
> +++ v3.11-rc1/include/linux/hugetlb.h
> @@ -66,6 +66,9 @@ int hugetlb_reserve_pages(struct inode *inode, long from, long to,
>                                                 vm_flags_t vm_flags);
>  void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed);
>  int dequeue_hwpoisoned_huge_page(struct page *page);
> +bool isolate_huge_page(struct page *page, struct list_head *l);
> +void putback_active_hugepage(struct page *page);
> +void putback_active_hugepages(struct list_head *l);
>  void copy_huge_page(struct page *dst, struct page *src);
>
>  #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
> @@ -134,6 +137,9 @@ static inline int dequeue_hwpoisoned_huge_page(struct page *page)
>         return 0;
>  }
>
> +#define isolate_huge_page(p, l) false
> +#define putback_active_hugepage(p)

Add do{}while(o), ok?

> +#define putback_active_hugepages(l)
>  static inline void copy_huge_page(struct page *dst, struct page *src)
>  {
>  }
> diff --git v3.11-rc1.orig/mm/hugetlb.c v3.11-rc1/mm/hugetlb.c
> index 83aff0a..4c48a70 100644
> --- v3.11-rc1.orig/mm/hugetlb.c
> +++ v3.11-rc1/mm/hugetlb.c
> @@ -48,7 +48,8 @@ static unsigned long __initdata default_hstate_max_huge_pages;
>  static unsigned long __initdata default_hstate_size;
>
>  /*
> - * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
> + * Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
> + * free_huge_pages, and surplus_huge_pages.
>   */
>  DEFINE_SPINLOCK(hugetlb_lock);
>
> @@ -3431,3 +3432,32 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
>         return ret;
>  }
>  #endif
> +
> +bool isolate_huge_page(struct page *page, struct list_head *l)

Can we replace the page parameter with p?

> +{
> +       VM_BUG_ON(!PageHead(page));
> +       if (!get_page_unless_zero(page))
> +               return false;
> +       spin_lock(&hugetlb_lock);
> +       list_move_tail(&page->lru, l);
> +       spin_unlock(&hugetlb_lock);
> +       return true;
> +}
> +
> +void putback_active_hugepage(struct page *page)
> +{
> +       VM_BUG_ON(!PageHead(page));
> +       spin_lock(&hugetlb_lock);
> +       list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist);
> +       spin_unlock(&hugetlb_lock);
> +       put_page(page);
> +}
> +
> +void putback_active_hugepages(struct list_head *l)
> +{
> +       struct page *page;
> +       struct page *page2;
> +
> +       list_for_each_entry_safe(page, page2, l, lru)
> +               putback_active_hugepage(page);

Can we acquire hugetlb_lock only once?

> +}
> diff --git v3.11-rc1.orig/mm/migrate.c v3.11-rc1/mm/migrate.c
> index 6f0c244..b44a067 100644
> --- v3.11-rc1.orig/mm/migrate.c
> +++ v3.11-rc1/mm/migrate.c
> @@ -100,6 +100,10 @@ void putback_movable_pages(struct list_head *l)
>         struct page *page2;
>
>         list_for_each_entry_safe(page, page2, l, lru) {
> +               if (unlikely(PageHuge(page))) {
> +                       putback_active_hugepage(page);
> +                       continue;
> +               }
>                 list_del(&page->lru);
>                 dec_zone_page_state(page, NR_ISOLATED_ANON +
>                                 page_is_file_cache(page));
> @@ -1025,7 +1029,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
>                 list_for_each_entry_safe(page, page2, from, lru) {
>                         cond_resched();
>
> -                       rc = unmap_and_move(get_new_page, private,
> +                       if (PageHuge(page))
> +                               rc = unmap_and_move_huge_page(get_new_page,
> +                                               private, page, pass > 2, mode);
> +                       else
> +                               rc = unmap_and_move(get_new_page, private,
>                                                 page, pass > 2, mode);
>
Is this hunk unclean merge?

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