[PATCH v2 07/10] thp: implement splitting pmd for huge zero page
From: Kirill A. Shutemov <hidden>
Date: 2012-09-10 13:14:48
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> We can't split huge zero page itself, but we can split the pmd which points to it. On splitting the pmd we create a table with all ptes set to normal zero page. Signed-off-by: Kirill A. Shutemov <redacted> --- mm/huge_memory.c | 32 ++++++++++++++++++++++++++++++++ 1 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 48ecc46..995894f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c@@ -1599,6 +1599,7 @@ int split_huge_page(struct page *page) struct anon_vma *anon_vma; int ret = 1; + BUG_ON(is_huge_zero_pfn(page_to_pfn(page))); BUG_ON(!PageAnon(page)); anon_vma = page_lock_anon_vma(page); if (!anon_vma)
@@ -2503,6 +2504,32 @@ static int khugepaged(void *none) return 0; } +static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd) +{ + pgtable_t pgtable; + pmd_t _pmd; + int i; + + pmdp_clear_flush_notify(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = get_pmd_huge_pte(vma->vm_mm); + pmd_populate(vma->vm_mm, &_pmd, pgtable); + + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + entry = pte_mkspecial(entry); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(vma->vm_mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(vma->vm_mm, pmd, pgtable); +} + void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd) {
@@ -2516,6 +2543,11 @@ void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, spin_unlock(&vma->vm_mm->page_table_lock); return; } + if (is_huge_zero_pmd(*pmd)) { + __split_huge_zero_page_pmd(vma, haddr, pmd); + spin_unlock(&vma->vm_mm->page_table_lock); + return; + } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page);
--
1.7.7.6
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