From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx187.postini.com [74.125.245.187]) by kanga.kvack.org (Postfix) with SMTP id 0850E6B006E for ; Thu, 9 Aug 2012 05:08:40 -0400 (EDT) From: "Kirill A. Shutemov" Subject: [PATCH, RFC 7/9] thp: implement splitting pmd for huge zero page Date: Thu, 9 Aug 2012 12:08:18 +0300 Message-Id: <1344503300-9507-8-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1344503300-9507-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1344503300-9507-1-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" , "Kirill A. Shutemov" From: "Kirill A. Shutemov" 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 --- mm/huge_memory.c | 36 ++++++++++++++++++++++++++++++++++++ 1 files changed, 36 insertions(+), 0 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c8948d6..4df5841 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 +2504,36 @@ static int khugepaged(void *none) return 0; } +static void __split_huge_zero_page_pmd(struct mm_struct *mm, pmd_t *pmd, + unsigned long address) +{ + pgtable_t pgtable; + pmd_t _pmd; + unsigned long haddr = address & HPAGE_PMD_MASK; + struct vm_area_struct *vma; + int i; + + vma = find_vma(mm, address); + VM_BUG_ON(vma == NULL); + pmdp_clear_flush_notify(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = get_pmd_huge_pte(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 mm_struct *mm, pmd_t *pmd, unsigned long address) { @@ -2513,6 +2544,11 @@ void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd, spin_unlock(&mm->page_table_lock); return; } + if (is_huge_zero_pmd(*pmd)) { + __split_huge_zero_page_pmd(mm, pmd, address); + spin_unlock(&mm->page_table_lock); + return; + } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page); -- 1.7.7.6 -- 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