[PATCH v4 03/10] thp: copy_huge_pmd(): copy huge zero page
From: Kirill A. Shutemov <hidden>
Date: 2012-10-15 06:02:40
Also in:
lkml
Subsystem:
memory management, memory management - thp (transparent huge page), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds
From: "Kirill A. Shutemov" <redacted> It's easy to copy huge zero page. Just set destination pmd to huge zero page. It's safe to copy huge zero page since we have none yet :-p Signed-off-by: Kirill A. Shutemov <redacted> --- mm/huge_memory.c | 17 +++++++++++++++++ 1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 680c27f..9f5e5cb 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -700,6 +700,18 @@ static inline struct page *alloc_hugepage(int defrag) } #endif +static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd) +{ + pmd_t entry; + entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot); + entry = pmd_wrprotect(entry); + entry = pmd_mkhuge(entry); + set_pmd_at(mm, haddr, pmd, entry); + pgtable_trans_huge_deposit(mm, pgtable); + mm->nr_ptes++; +} + int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags)
@@ -777,6 +789,11 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte_free(dst_mm, pgtable); goto out_unlock; } + if (is_huge_zero_pmd(pmd)) { + set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd); + ret = 0; + goto out_unlock; + } if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(&src_mm->page_table_lock);
--
1.7.7.6
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