From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx206.postini.com [74.125.245.206]) by kanga.kvack.org (Postfix) with SMTP id 63E7C6B0071 for ; Fri, 26 Oct 2012 05:49:22 -0400 (EDT) Received: by mail-ia0-f169.google.com with SMTP id h37so2607665iak.14 for ; Fri, 26 Oct 2012 02:49:21 -0700 (PDT) Message-ID: <508A5C94.3030003@gmail.com> Date: Fri, 26 Oct 2012 17:49:08 +0800 From: Ni zhan Chen MIME-Version: 1.0 Subject: Re: [PATCH v3] mm: thp: Set the accessed flag for old pages on access fault. References: <1351183471-14710-1-git-send-email-will.deacon@arm.com> <508A2B8B.7020608@gmail.com> <20121026093407.GD20914@mudshark.cambridge.arm.com> In-Reply-To: <20121026093407.GD20914@mudshark.cambridge.arm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "mhocko@suse.cz" , "peterz@infradead.org" , "akpm@linux-foundation.org" , Chris Metcalf , "Kirill A. Shutemov" , Andrea Arcangeli On 10/26/2012 05:34 PM, Will Deacon wrote: > On Fri, Oct 26, 2012 at 07:19:55AM +0100, Ni zhan Chen wrote: >> On 10/26/2012 12:44 AM, Will Deacon wrote: >>> On x86 memory accesses to pages without the ACCESSED flag set result in the >>> ACCESSED flag being set automatically. With the ARM architecture a page access >>> fault is raised instead (and it will continue to be raised until the ACCESSED >>> flag is set for the appropriate PTE/PMD). >>> >>> For normal memory pages, handle_pte_fault will call pte_mkyoung (effectively >>> setting the ACCESSED flag). For transparent huge pages, pmd_mkyoung will only >>> be called for a write fault. >>> >>> This patch ensures that faults on transparent hugepages which do not result >>> in a CoW update the access flags for the faulting pmd. >> Could you write changlog? > >From v2? I included something below my SoB. The code should do exactly the > same as before, it's just rebased onto next so that I can play nicely with > Peter's patches. > >>> Cc: Chris Metcalf >>> Cc: Kirill A. Shutemov >>> Cc: Andrea Arcangeli >>> Signed-off-by: Will Deacon >>> --- >>> >>> Ok chaps, I rebased this thing onto today's next (which basically >>> necessitated a rewrite) so I've reluctantly dropped my acks and kindly >>> ask if you could eyeball the new code, especially where the locking is >>> concerned. In the numa code (do_huge_pmd_prot_none), Peter checks again >>> that the page is not splitting, but I can't see why that is required. >>> >>> Cheers, >>> >>> Will >> Could you explain why you not call pmd_trans_huge_lock to confirm the >> pmd is splitting or stable as Andrea point out? > The way handle_mm_fault is now structured after the numa changes means that > we only enter the huge pmd page aging code if the entry wasn't splitting Why you call it huge pmd page *aging* code? Regards, Chen > before taking the lock, so it seemed a bit gratuitous to jump through those > hoops again in pmd_trans_huge_lock. > > Will > -- 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