From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753696Ab2HIJIn (ORCPT ); Thu, 9 Aug 2012 05:08:43 -0400 Received: from mga01.intel.com ([192.55.52.88]:55218 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328Ab2HIJIk (ORCPT ); Thu, 9 Aug 2012 05:08:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,739,1336374000"; d="scan'208";a="205376420" From: "Kirill A. Shutemov" 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" Subject: [PATCH, RFC 3/9] thp: copy_huge_pmd(): copy huge zero page Date: Thu, 9 Aug 2012 12:08:14 +0300 Message-Id: <1344503300-9507-4-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 1.7.10.4 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" 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 --- 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 9dcb9e6..a534f84 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -725,6 +725,18 @@ 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); + prepare_pmd_huge_pte(pgtable, mm); + 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) @@ -802,6 +814,11 @@ 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