From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Aneesh Kumar K.V" Subject: Re: [PATCHv2 3/3] mm: Use updated pmdp_invalidate() inteface to track dirty/accessed bits Date: Fri, 16 Jun 2017 21:27:04 +0530 Message-ID: References: <20170615145224.66200-1-kirill.shutemov@linux.intel.com> <20170615145224.66200-4-kirill.shutemov@linux.intel.com> <87bmpob23x.fsf@skywalker.in.ibm.com> <20170616132143.cdr4qt5hzvgxsnek@node.shutemov.name> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:40153 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750798AbdFPP5Y (ORCPT ); Fri, 16 Jun 2017 11:57:24 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v5GFrakT127663 for ; Fri, 16 Jun 2017 11:57:24 -0400 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0b-001b2d01.pphosted.com with ESMTP id 2b4g5np2nk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 16 Jun 2017 11:57:23 -0400 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 16 Jun 2017 11:57:23 -0400 In-Reply-To: <20170616132143.cdr4qt5hzvgxsnek@node.shutemov.name> Content-Language: en-US Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrew Morton , Vlastimil Babka , Vineet Gupta , Russell King , Will Deacon , Catalin Marinas , Ralf Baechle , "David S. Miller" , Martin Schwidefsky , Heiko Carstens , Andrea Arcangeli , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Friday 16 June 2017 06:51 PM, Kirill A. Shutemov wrote: > On Fri, Jun 16, 2017 at 05:01:30PM +0530, Aneesh Kumar K.V wrote: >> "Kirill A. Shutemov" writes: >> >>> This patch uses modifed pmdp_invalidate(), that return previous value of pmd, >>> to transfer dirty and accessed bits. >>> >>> Signed-off-by: Kirill A. Shutemov >>> --- >>> fs/proc/task_mmu.c | 8 ++++---- >>> mm/huge_memory.c | 29 ++++++++++++----------------- >>> 2 files changed, 16 insertions(+), 21 deletions(-) >>> >>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >>> index f0c8b33d99b1..f2fc1ef5bba2 100644 >>> --- a/fs/proc/task_mmu.c >>> +++ b/fs/proc/task_mmu.c >> >> ..... >> >>> @@ -1965,7 +1955,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, >>> page_ref_add(page, HPAGE_PMD_NR - 1); >>> write = pmd_write(*pmd); >>> young = pmd_young(*pmd); >>> - dirty = pmd_dirty(*pmd); >>> soft_dirty = pmd_soft_dirty(*pmd); >>> >>> pmdp_huge_split_prepare(vma, haddr, pmd); >>> @@ -1995,8 +1984,6 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, >>> if (soft_dirty) >>> entry = pte_mksoft_dirty(entry); >>> } >>> - if (dirty) >>> - SetPageDirty(page + i); >>> pte = pte_offset_map(&_pmd, addr); >>> BUG_ON(!pte_none(*pte)); >>> set_pte_at(mm, addr, pte, entry); >>> @@ -2045,7 +2032,15 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, >>> * and finally we write the non-huge version of the pmd entry with >>> * pmd_populate. >>> */ >>> - pmdp_invalidate(vma, haddr, pmd); >>> + old = pmdp_invalidate(vma, haddr, pmd); >>> + >>> + /* >>> + * Transfer dirty bit using value returned by pmd_invalidate() to be >>> + * sure we don't race with CPU that can set the bit under us. >>> + */ >>> + if (pmd_dirty(old)) >>> + SetPageDirty(page); >>> + >>> pmd_populate(mm, pmd, pgtable); >>> >>> if (freeze) { >> >> >> Can we invalidate the pmd early here ? ie, do pmdp_invalidate instead of >> pmdp_huge_split_prepare() ? > > I think we can. But it means we would block access to the page for longer > than it's necessary on most architectures. I guess it's not a bit deal. > > Maybe as separate patch on top of this patchet? Aneesh, would you take > care of this? > Yes, I cam do that. -aneesh