From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx142.postini.com [74.125.245.142]) by kanga.kvack.org (Postfix) with SMTP id AAF346B0044 for ; Thu, 11 Oct 2012 23:23:43 -0400 (EDT) Received: by mail-ob0-f169.google.com with SMTP id va7so2959701obc.14 for ; Thu, 11 Oct 2012 20:23:42 -0700 (PDT) Message-ID: <50778D39.1000102@gmail.com> Date: Fri, 12 Oct 2012 11:23:37 +0800 From: Ni zhan Chen MIME-Version: 1.0 Subject: Re: [PATCH v3 07/10] thp: implement splitting pmd for huge zero page References: <1349191172-28855-1-git-send-email-kirill.shutemov@linux.intel.com> <1349191172-28855-8-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1349191172-28855-8-git-send-email-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrew Morton , linux-mm@kvack.org, Andrea Arcangeli , Andi Kleen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" On 10/02/2012 11:19 PM, Kirill A. Shutemov wrote: > 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 > Reviewed-by: Andrea Arcangeli > --- > 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); -- 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