From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx165.postini.com [74.125.245.165]) by kanga.kvack.org (Postfix) with SMTP id 6EA726B0073 for ; Thu, 15 Nov 2012 14:26:00 -0500 (EST) From: "Kirill A. Shutemov" Subject: [PATCH v6 07/12] thp: implement splitting pmd for huge zero page Date: Thu, 15 Nov 2012 21:26:57 +0200 Message-Id: <1353007622-18393-8-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1353007622-18393-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1353007622-18393-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Andrea Arcangeli , linux-mm@kvack.org Cc: Andi Kleen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , David Rientjes , "Kirill A. Shutemov" From: "Kirill A. Shutemov" We can't split huge zero page itself (and it's bug if we try), 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 --- mm/huge_memory.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2e1dbba..015a13a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1597,6 +1597,7 @@ 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) @@ -2495,24 +2496,64 @@ 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) +{ + struct mm_struct *mm = vma->vm_mm; + pgtable_t pgtable; + pmd_t _pmd; + int i; + + pmdp_clear_flush(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = pgtable_trans_huge_withdraw(mm); + pmd_populate(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(mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); +} + void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd) { struct page *page; unsigned long haddr = address & HPAGE_PMD_MASK; struct mm_struct *mm = vma->vm_mm; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_trans_huge(*pmd))) { spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + return; + } + if (is_huge_zero_pmd(*pmd)) { + __split_huge_zero_page_pmd(vma, haddr, pmd); + spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); return; } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page); spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); split_huge_page(page); -- 1.7.11.7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org