From b65d4adbc0f0d4619f61ee9d8126bc5005b78802 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Wed, 30 Jun 2021 18:47:17 -0700 Subject: mm: hugetlb: defer freeing of HugeTLB pages In the subsequent patch, we should allocate the vmemmap pages when freeing a HugeTLB page. But update_and_free_page() can be called under any context, so we cannot use GFP_KERNEL to allocate vmemmap pages. However, we can defer the actual freeing in a kworker to prevent from using GFP_ATOMIC to allocate the vmemmap pages. The __update_and_free_page() is where the call to allocate vmemmmap pages will be inserted. Link: https://lkml.kernel.org/r/20210510030027.56044-6-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz Reviewed-by: Oscar Salvador Cc: Alexander Viro Cc: Andy Lutomirski Cc: Anshuman Khandual Cc: Balbir Singh Cc: Barry Song Cc: Bodeddula Balasubramaniam Cc: Borislav Petkov Cc: Chen Huang Cc: Dave Hansen Cc: David Hildenbrand Cc: David Rientjes Cc: HORIGUCHI NAOYA Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Joao Martins Cc: Joerg Roedel Cc: Jonathan Corbet Cc: Matthew Wilcox Cc: Miaohe Lin Cc: Michal Hocko Cc: Mina Almasry Cc: Oliver Neukum Cc: Paul E. McKenney Cc: Pawan Gupta Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Thomas Gleixner Cc: Xiongchun Duan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 76 insertions(+), 7 deletions(-) (limited to 'mm/hugetlb.c') diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 5f5493f0f003..e7eb1ab8c78a 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1376,7 +1376,7 @@ static void remove_hugetlb_page(struct hstate *h, struct page *page, h->nr_huge_pages_node[nid]--; } -static void update_and_free_page(struct hstate *h, struct page *page) +static void __update_and_free_page(struct hstate *h, struct page *page) { int i; struct page *subpage = page; @@ -1399,12 +1399,79 @@ static void update_and_free_page(struct hstate *h, struct page *page) } } +/* + * As update_and_free_page() can be called under any context, so we cannot + * use GFP_KERNEL to allocate vmemmap pages. However, we can defer the + * actual freeing in a workqueue to prevent from using GFP_ATOMIC to allocate + * the vmemmap pages. + * + * free_hpage_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 free_hpage_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_freelist); + +static void free_hpage_workfn(struct work_struct *work) +{ + struct llist_node *node; + + node = llist_del_all(&hpage_freelist); + + while (node) { + struct page *page; + struct hstate *h; + + page = container_of((struct address_space **)node, + struct page, mapping); + node = node->next; + page->mapping = NULL; + /* + * The VM_BUG_ON_PAGE(!PageHuge(page), page) in page_hstate() + * is going to trigger because a previous call to + * remove_hugetlb_page() will set_compound_page_dtor(page, + * NULL_COMPOUND_DTOR), so do not use page_hstate() directly. + */ + h = size_to_hstate(page_size(page)); + + __update_and_free_page(h, page); + + cond_resched(); + } +} +static DECLARE_WORK(free_hpage_work, free_hpage_workfn); + +static inline void flush_free_hpage_work(struct hstate *h) +{ + if (free_vmemmap_pages_per_hpage(h)) + flush_work(&free_hpage_work); +} + +static void update_and_free_page(struct hstate *h, struct page *page, + bool atomic) +{ + if (!free_vmemmap_pages_per_hpage(h) || !atomic) { + __update_and_free_page(h, page); + return; + } + + /* + * Defer freeing to avoid using GFP_ATOMIC to allocate vmemmap pages. + * + * Only call schedule_work() if hpage_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_freelist)) + schedule_work(&free_hpage_work); +} + static void update_and_free_pages_bulk(struct hstate *h, struct list_head *list) { struct page *page, *t_page; list_for_each_entry_safe(page, t_page, list, lru) { - update_and_free_page(h, page); + update_and_free_page(h, page, false); cond_resched(); } } @@ -1471,12 +1538,12 @@ void free_huge_page(struct page *page) if (HPageTemporary(page)) { remove_hugetlb_page(h, page, false); spin_unlock_irqrestore(&hugetlb_lock, flags); - update_and_free_page(h, page); + update_and_free_page(h, page, true); } else if (h->surplus_huge_pages_node[nid]) { /* remove the page from active list */ remove_hugetlb_page(h, page, true); spin_unlock_irqrestore(&hugetlb_lock, flags); - update_and_free_page(h, page); + update_and_free_page(h, page, true); } else { arch_clear_hugepage_flags(page); enqueue_huge_page(h, page); @@ -1795,7 +1862,7 @@ retry: remove_hugetlb_page(h, head, false); h->max_huge_pages--; spin_unlock_irq(&hugetlb_lock); - update_and_free_page(h, head); + update_and_free_page(h, head, false); return 0; } out: @@ -2411,14 +2478,14 @@ retry: * Pages have been replaced, we can safely free the old one. */ spin_unlock_irq(&hugetlb_lock); - update_and_free_page(h, old_page); + update_and_free_page(h, old_page, false); } return ret; free_new: spin_unlock_irq(&hugetlb_lock); - update_and_free_page(h, new_page); + update_and_free_page(h, new_page, false); return ret; } @@ -2832,6 +2899,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, * pages in hstate via the proc/sysfs interfaces. */ mutex_lock(&h->resize_lock); + flush_free_hpage_work(h); spin_lock_irq(&hugetlb_lock); /* @@ -2941,6 +3009,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, /* free the pages after dropping lock */ spin_unlock_irq(&hugetlb_lock); update_and_free_pages_bulk(h, &page_list); + flush_free_hpage_work(h); spin_lock_irq(&hugetlb_lock); while (count < persistent_huge_pages(h)) { -- cgit v1.2.3-58-ga151