Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755340AbaJNL5n (ORCPT ); Tue, 14 Oct 2014 07:57:43 -0400 Received: from mta-out1.inet.fi ([62.71.2.234]:41583 "EHLO jenni2.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754881AbaJNL5m (ORCPT ); Tue, 14 Oct 2014 07:57:42 -0400 Date: Tue, 14 Oct 2014 14:57:30 +0300 From: "Kirill A. Shutemov" To: Fengwei Yin Cc: Dave Hansen , LKML , linux-mm@kvack.org, fengguang.wu@intel.com, "Kirill A. Shutemov" Subject: Re: [PATCH] smaps should deal with huge zero page exactly same as normal zero page Message-ID: <20141014115730.GB6524@node.dhcp.inet.fi> References: <5436B98E.1070407@intel.com> <20141010132027.GB25038@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141010132027.GB25038@gmail.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 10, 2014 at 09:21:08PM +0800, Fengwei Yin wrote: > On Thu, Oct 09, 2014 at 09:36:30AM -0700, Dave Hansen wrote: > > On 10/09/2014 02:19 AM, Fengwei Yin wrote: > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > > > index 80ca4fb..8550b27 100644 > > > --- a/fs/proc/task_mmu.c > > > +++ b/fs/proc/task_mmu.c > > > @@ -476,7 +476,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr, > > > mss->nonlinear += ptent_size; > > > } > > > > > > - if (!page) > > > + if (!page || is_huge_zero_page(page)) > > > return; > > > > This really seems like a bit of a hack. A normal (small) zero page > > won't make it to this point because of the vm_normal_page() check in > > smaps_pte_entry() which hits the _PAGE_SPECIAL bit in the pte. > > > > Is there a reason we can't set _PAGE_SPECIAL on the huge_zero_page ptes? > > If we did that, we wouldn't need a special case here. > > > > If we can't do that for some reason, can we at least teach > > vm_normal_page() about the huge_zero_page in some other way? > I suppose _PAGE_SPECIAL can't work. Two reasons: > 1. Not all arch have HAVE_PTE_SPECIAL set. So always need another way to > handle the arch which has no PTE_SPECIAL. > 2. _PAGE_SPECIAL is just for PTE now. If want to add it for huge page, > we need to introduce pmd_mkspecial() thing which I don't think it's > worth to do now (unless you want it. :)). > > Yes. We could move the check to vm_normal_page(). But it still needs > export functions from huge_memory.c. > > Please check the new patch. > > > > > > if (PageAnon(page)) > > > @@ -516,7 +516,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > > > if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { > > > smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk); > > > spin_unlock(ptl); > > > - mss->anonymous_thp += HPAGE_PMD_SIZE; > > > + if (!is_huge_zero_pmd(*pmd)) > > > + mss->anonymous_thp += HPAGE_PMD_SIZE; > > > return 0; > > > } > > > > How about we just move this hunk in to smaps_pte_entry()? Something > > along these lines: > > > > ... > > if (PageAnon(page)) { > > mss->anonymous += ptent_size; > > + if (PageTransHuge(page)) > > + mss->anonymous_thp += ptent_size; > > } > Done. > > > > If we do that, plus teaching vm_normal_page() about huge_zero_pages, it > > will help keep the hacks and the extra code due to huge pages to a miniumum. > > > > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > > > index 63579cb..758f569 100644 > > > --- a/include/linux/huge_mm.h > > > +++ b/include/linux/huge_mm.h > > > @@ -34,6 +34,10 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > > > unsigned long addr, pgprot_t newprot, > > > int prot_numa); > > > > > > +extern bool is_huge_zero_page(struct page *page); > > > + > > > +extern bool is_huge_zero_pmd(pmd_t pmd); > > > + > > > enum transparent_hugepage_flag { > > > TRANSPARENT_HUGEPAGE_FLAG, > > > TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > index d9a21d06..bedc3ae 100644 > > > --- a/mm/huge_memory.c > > > +++ b/mm/huge_memory.c > > > @@ -173,12 +173,12 @@ static int start_khugepaged(void) > > > static atomic_t huge_zero_refcount; > > > static struct page *huge_zero_page __read_mostly; > > > > > > -static inline bool is_huge_zero_page(struct page *page) > > > +bool is_huge_zero_page(struct page *page) > > > { > > > return ACCESS_ONCE(huge_zero_page) == page; > > > } > > > > > > -static inline bool is_huge_zero_pmd(pmd_t pmd) > > > +bool is_huge_zero_pmd(pmd_t pmd) > > > { > > > return is_huge_zero_page(pmd_page(pmd)); > > > } > > > > ^^^ And all these exports. > > A new function is_huge_zero_pfn() is added to mm/huge_memory.c > and exported. > > Thanks. > From 4e7bdd5bc22874175982ab50303eab32843c753c Mon Sep 17 00:00:00 2001 > From: Fengwei Yin > Date: Thu, 9 Oct 2014 22:20:58 +0800 > Subject: [PATCH] smaps should deal with huge zero page exactly same as normal > zero page. > Description? > Signed-off-by: Fengwei Yin > --- > fs/proc/task_mmu.c | 6 ++++-- > include/linux/huge_mm.h | 2 ++ > mm/huge_memory.c | 5 +++++ > mm/memory.c | 4 ++++ > 4 files changed, 15 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index c341568..fb19c0c 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -471,8 +471,11 @@ static void smaps_pte_entry(pte_t ptent, unsigned long addr, > if (!page) > return; > > - if (PageAnon(page)) > + if (PageAnon(page)) { > mss->anonymous += ptent_size; > + if (PageTransHuge(page)) > + mss->anonymous_thp += HPAGE_PMD_SIZE; > + } > > if (page->index != pgoff) > mss->nonlinear += ptent_size; > @@ -508,7 +511,6 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { > smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk); > spin_unlock(ptl); > - mss->anonymous_thp += HPAGE_PMD_SIZE; > return 0; > } > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 63579cb..9bf6263 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -34,6 +34,8 @@ extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > unsigned long addr, pgprot_t newprot, > int prot_numa); > > +extern bool is_huge_zero_pfn(unsigned long pfn); > + > enum transparent_hugepage_flag { > TRANSPARENT_HUGEPAGE_FLAG, > TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index f8ffd94..71ca4ed 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -183,6 +183,11 @@ static inline bool is_huge_zero_pmd(pmd_t pmd) > return is_huge_zero_page(pmd_page(pmd)); > } > > +inline bool is_huge_zero_pfn(unsigned long pfn) There's no way the function can be inlined. Otherwise looks good to me. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/