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But update_and_free_page() is be called from a non-task context(and hold hugetlb_lock), 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 | 98 +++++++++++++++++++++++++++++++++++++++++++++------- mm/hugetlb_vmemmap.c | 5 --- mm/hugetlb_vmemmap.h | 10 ++++++ 3 files changed, 96 insertions(+), 17 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a0ce6f33a717..4aabf12aca9b 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1221,7 +1221,7 @@ static void destroy_compound_gigantic_page(struct page *page, __ClearPageHead(page); } -static void free_gigantic_page(struct page *page, unsigned int order) +static void __free_gigantic_page(struct page *page, unsigned int order) { /* * If the page isn't allocated using the cma allocator, @@ -1288,20 +1288,100 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask, { return NULL; } -static inline void free_gigantic_page(struct page *page, unsigned int order) { } +static inline void __free_gigantic_page(struct page *page, + unsigned int order) { } static inline void destroy_compound_gigantic_page(struct page *page, unsigned int order) { } #endif -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 hold + * hugetlb_lock), we can defer the actual freeing in a workqueue to prevent + * 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 pointer + * 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 = llist_del_all(&hpage_update_freelist); + + while (node) { + page = container_of((struct address_space **)node, + struct page, mapping); + node = node->next; + page->mapping = 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); +} + +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP +static inline void free_gigantic_page(struct hstate *h, struct page *page) +{ + __free_gigantic_page(page, huge_page_order(h)); +} +#else +static inline void free_gigantic_page(struct hstate *h, struct page *page) +{ + /* + * Temporarily drop the hugetlb_lock, because + * we might block in __free_gigantic_page(). + */ + spin_unlock(&hugetlb_lock); + __free_gigantic_page(page, huge_page_order(h)); + spin_lock(&hugetlb_lock); +} +#endif + +static void update_and_free_page(struct hstate *h, struct page *page) +{ if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return; 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 = 0; i < pages_per_huge_page(h); i++) { page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced | 1 << PG_dirty | @@ -1313,14 +1393,8 @@ static void update_and_free_page(struct hstate *h, struct page *page) set_compound_page_dtor(page, NULL_COMPOUND_DTOR); set_page_refcounted(page); if (hstate_is_gigantic(h)) { - /* - * Temporarily drop the hugetlb_lock, because - * we might block in free_gigantic_page(). - */ - 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); + free_gigantic_page(h, page); } else { __free_pages(page, huge_page_order(h)); } @@ -1761,7 +1835,7 @@ static struct page *alloc_fresh_huge_page(struct hstate *h, if (vmemmap_pgtable_prealloc(h, page)) { if (hstate_is_gigantic(h)) - free_gigantic_page(page, huge_page_order(h)); + free_gigantic_page(h, page); else put_page(page); return NULL; diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 937562a15f1e..e6fca02b57b2 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -115,11 +115,6 @@ static inline bool vmemmap_pmd_huge(pmd_t *pmd) } #endif -static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h) -{ - return h->nr_free_vmemmap_pages; -} - static inline unsigned int vmemmap_pages_per_hpage(struct hstate *h) { return free_vmemmap_pages_per_hpage(h) + RESERVE_VMEMMAP_NR; diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h index fb8b77659ed5..a23fb1375859 100644 --- a/mm/hugetlb_vmemmap.h +++ b/mm/hugetlb_vmemmap.h @@ -16,6 +16,11 @@ void __init hugetlb_vmemmap_init(struct hstate *h); int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page); void vmemmap_pgtable_free(struct page *page); void free_huge_page_vmemmap(struct hstate *h, struct page *head); + +static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h) +{ + return h->nr_free_vmemmap_pages; +} #else static inline void hugetlb_vmemmap_init(struct hstate *h) { @@ -33,5 +38,10 @@ static inline void vmemmap_pgtable_free(struct page *page) 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 */