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Date: Mon, 25 Mar 2013 11:57:01 +0100
From: Michal Hocko <mhocko@...e.cz>
To: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Andi Kleen <andi@...stfloor.org>,
Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/10] migrate: make core migration code aware of hugepage
On Fri 22-03-13 16:23:47, Naoya Horiguchi wrote:
> Before enabling each user of page migration to support hugepage,
> this patch adds necessary changes on core migration code.
> The main change is that the list of pages to migrate can link
> not only LRU pages, but also hugepages.
> Along with this, functions such as migrate_pages() and
> putback_movable_pages() need to be changed to handle hugepages.
>
> 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@...jp.nec.com>
> ---
> include/linux/hugetlb.h | 4 ++++
> include/linux/migrate.h | 6 ++++++
> mm/hugetlb.c | 21 ++++++++++++++++++++-
> mm/migrate.c | 24 +++++++++++++++++++++++-
> 4 files changed, 53 insertions(+), 2 deletions(-)
>
> diff --git v3.9-rc3.orig/include/linux/hugetlb.h v3.9-rc3/include/linux/hugetlb.h
> index 16e4e9a..baa0aa0 100644
> --- v3.9-rc3.orig/include/linux/hugetlb.h
> +++ v3.9-rc3/include/linux/hugetlb.h
> @@ -66,6 +66,8 @@ 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);
> +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);
>
> extern unsigned long hugepages_treat_as_movable;
> @@ -128,6 +130,8 @@ static inline int dequeue_hwpoisoned_huge_page(struct page *page)
> return 0;
> }
>
> +#define putback_active_hugepage(p) 0
> +#define putback_active_hugepages(l) 0
> static inline void copy_huge_page(struct page *dst, struct page *src)
> {
> }
> diff --git v3.9-rc3.orig/include/linux/migrate.h v3.9-rc3/include/linux/migrate.h
> index a405d3dc..d4c6c08 100644
> --- v3.9-rc3.orig/include/linux/migrate.h
> +++ v3.9-rc3/include/linux/migrate.h
> @@ -41,6 +41,9 @@ extern int migrate_page(struct address_space *,
> struct page *, struct page *, enum migrate_mode);
> extern int migrate_pages(struct list_head *l, new_page_t x,
> unsigned long private, enum migrate_mode mode, int reason);
> +extern int migrate_movable_pages(struct list_head *from,
> + new_page_t get_new_page, unsigned long private,
> + enum migrate_mode mode, int reason);
> extern int migrate_huge_page(struct page *, new_page_t x,
> unsigned long private, enum migrate_mode mode);
>
> @@ -62,6 +65,9 @@ static inline void putback_movable_pages(struct list_head *l) {}
> static inline int migrate_pages(struct list_head *l, new_page_t x,
> unsigned long private, enum migrate_mode mode, int reason)
> { return -ENOSYS; }
> +static inline int migrate_movable_pages(struct list_head *from,
> + new_page_t get_new_page, unsigned long private, bool offlining,
> + enum migrate_mode mode, int reason) { return -ENOSYS; }
> static inline int migrate_huge_page(struct page *page, new_page_t x,
> unsigned long private, enum migrate_mode mode)
> { return -ENOSYS; }
> diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c
> index 98a478e..a787c44 100644
> --- v3.9-rc3.orig/mm/hugetlb.c
> +++ v3.9-rc3/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.
> */
Could you get this out into a separate patch and add lockdep assertions
to functions which do not lock it directly but they rely on it so that
the locking is more clear?
e.g. dequeue_huge_page_node, update_and_free_page, try_to_free_low, ...
It would a nice cleanup and a lead for future when somebody tries to
make the locking a bit saner.
> DEFINE_SPINLOCK(hugetlb_lock);
>
> @@ -3182,3 +3183,21 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
> return ret;
> }
> #endif
> +
> +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);
> +}
> diff --git v3.9-rc3.orig/mm/migrate.c v3.9-rc3/mm/migrate.c
> index ec692a3..f69f354 100644
> --- v3.9-rc3.orig/mm/migrate.c
> +++ v3.9-rc3/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));
> @@ -1023,7 +1027,11 @@ 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);
>
> switch(rc) {
> @@ -1056,6 +1064,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> return rc;
> }
>
> +int migrate_movable_pages(struct list_head *from, new_page_t get_new_page,
> + unsigned long private,
> + enum migrate_mode mode, int reason)
> +{
> + int err = 0;
> +
> + if (!list_empty(from)) {
> + err = migrate_pages(from, get_new_page, private, mode, reason);
> + if (err)
> + putback_movable_pages(from);
> + }
> + return err;
> +}
> +
There doesn't seem to be any caller for this function. Please move it to
the patch which uses it.
> int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
> unsigned long private, enum migrate_mode mode)
> {
> --
> 1.7.11.7
>
--
Michal Hocko
SUSE Labs
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