Messages in this thread | | | Date | Fri, 12 Oct 2012 11:23:37 +0800 | From | Ni zhan Chen <> | Subject | Re: [PATCH v3 07/10] thp: implement splitting pmd for huge zero page |
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On 10/02/2012 11:19 PM, Kirill A. Shutemov wrote: > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > > 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 <kirill.shutemov@linux.intel.com> > Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> > --- > 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 95032d3..3f1c59c 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1600,6 +1600,7 @@ 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);
why I can't find function pmdp_clear_flush_notify in kernel source code? Do you mean pmdp_clear_flush_young_notify or something like that?
> + /* 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);
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