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But update_and_free_page() is called from a non-task context(and hold hugetlb_lock), so we can defer the actual freeing in a workqueue to prevent use GFP_ATOMIC to allocate the vmemmap pages. Signed-off-by: Muchun Song --- mm/hugetlb.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++= ++---- mm/hugetlb_vmemmap.c | 12 -------- mm/hugetlb_vmemmap.h | 17 ++++++++++++ 3 files changed, 88 insertions(+), 18 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 140135fc8113..0ff9b90e524f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1292,15 +1292,76 @@ static inline void destroy_compound_gigantic_page= (struct page *page, unsigned int order) { } #endif =20 -static void update_and_free_page(struct hstate *h, struct page *page) +static void __free_hugepage(struct hstate *h, struct page *page); + +/* + * As update_and_free_page() is be called from a non-task context(and ho= ld + * hugetlb_lock), we can defer the actual freeing in a workqueue to prev= ent + * use GFP_ATOMIC to allocate a lot of vmemmap pages. + * + * update_hpage_vmemmap_workfn() locklessly retrieves the linked list of + * pages to be freed and frees them one-by-one. As the page->mapping poi= nter + * is going to be cleared in update_hpage_vmemmap_workfn() anyway, it is + * reused as the llist_node structure of a lockless linked list of huge + * pages to be freed. + */ +static LLIST_HEAD(hpage_update_freelist); + +static void update_hpage_vmemmap_workfn(struct work_struct *work) { - int i; + struct llist_node *node; + struct page *page; + + node =3D llist_del_all(&hpage_update_freelist); =20 + while (node) { + page =3D container_of((struct address_space **)node, + struct page, mapping); + node =3D node->next; + page->mapping =3D NULL; + __free_hugepage(page_hstate(page), page); + + cond_resched(); + } +} +static DECLARE_WORK(hpage_update_work, update_hpage_vmemmap_workfn); + +static inline void __update_and_free_page(struct hstate *h, struct page = *page) +{ + /* No need to allocate vmemmap pages */ + if (!free_vmemmap_pages_per_hpage(h)) { + __free_hugepage(h, page); + return; + } + + /* + * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap + * pages. + * + * Only call schedule_work() if hpage_update_freelist is previously + * empty. Otherwise, schedule_work() had been called but the workfn + * hasn't retrieved the list yet. + */ + if (llist_add((struct llist_node *)&page->mapping, + &hpage_update_freelist)) + schedule_work(&hpage_update_work); +} + +static void update_and_free_page(struct hstate *h, struct page *page) +{ if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return; =20 h->nr_huge_pages--; h->nr_huge_pages_node[page_to_nid(page)]--; + + __update_and_free_page(h, page); +} + +static void __free_hugepage(struct hstate *h, struct page *page) +{ + int i; + for (i =3D 0; i < pages_per_huge_page(h); i++) { page[i].flags &=3D ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced | 1 << PG_dirty | @@ -1313,13 +1374,17 @@ static void update_and_free_page(struct hstate *h= , struct page *page) set_page_refcounted(page); if (hstate_is_gigantic(h)) { /* - * Temporarily drop the hugetlb_lock, because - * we might block in free_gigantic_page(). + * Temporarily drop the hugetlb_lock only when this type of + * HugeTLB page does not support vmemmap optimization (which + * contex do not hold the hugetlb_lock), because we might block + * in free_gigantic_page(). */ - spin_unlock(&hugetlb_lock); + if (!free_vmemmap_pages_per_hpage(h)) + spin_unlock(&hugetlb_lock); destroy_compound_gigantic_page(page, huge_page_order(h)); free_gigantic_page(page, huge_page_order(h)); - spin_lock(&hugetlb_lock); + if (!free_vmemmap_pages_per_hpage(h)) + spin_lock(&hugetlb_lock); } else { __free_pages(page, huge_page_order(h)); } diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 5a714bd60d6b..6d4e77a2b6c7 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -180,18 +180,6 @@ #define RESERVE_VMEMMAP_NR 2U #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) =20 -/* - * How many vmemmap pages associated with a HugeTLB page that can be fre= ed - * to the buddy allocator. - * - * Todo: Returns zero for now, which means the feature is disabled. We w= ill - * enable it once all the infrastructure is there. - */ -static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h= ) -{ - return 0; -} - static inline unsigned long free_vmemmap_pages_size_per_hpage(struct hst= ate *h) { return (unsigned long)free_vmemmap_pages_per_hpage(h) << PAGE_SHIFT; diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h index 6923f03534d5..01f8637adbe0 100644 --- a/mm/hugetlb_vmemmap.h +++ b/mm/hugetlb_vmemmap.h @@ -12,9 +12,26 @@ =20 #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP void free_huge_page_vmemmap(struct hstate *h, struct page *head); + +/* + * How many vmemmap pages associated with a HugeTLB page that can be fre= ed + * to the buddy allocator. + * + * Todo: Returns zero for now, which means the feature is disabled. We w= ill + * enable it once all the infrastructure is there. + */ +static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h= ) +{ + return 0; +} #else static inline void free_huge_page_vmemmap(struct hstate *h, struct page = *head) { } + +static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h= ) +{ + return 0; +} #endif /* CONFIG_HUGETLB_PAGE_FREE_VMEMMAP */ #endif /* _LINUX_HUGETLB_VMEMMAP_H */ --=20 2.11.0