From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id 734176B0072 for ; Thu, 25 Oct 2012 23:08:10 -0400 (EDT) Received: by mail-ie0-f169.google.com with SMTP id 10so4029127ied.14 for ; Thu, 25 Oct 2012 20:08:09 -0700 (PDT) Message-ID: <5089FE8E.4030603@gmail.com> Date: Fri, 26 Oct 2012 11:07:58 +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> <20121025195110.GA4771@cmpxchg.org> In-Reply-To: <20121025195110.GA4771@cmpxchg.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Will Deacon , 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 03:51 AM, Johannes Weiner wrote: > On Thu, Oct 25, 2012 at 05:44:31PM +0100, 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. >> >> Cc: Chris Metcalf >> Cc: Kirill A. Shutemov >> Cc: Andrea Arcangeli >> Signed-off-by: Will Deacon > Acked-by: Johannes Weiner > >> 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. > I don't either. If the thing was splitting when the fault happened, > that path is not taken. And the locked pmd_same() check should rule > out splitting setting in after testing pmd_trans_huge_splitting(). Why I can't find function pmd_trans_huge_splitting() you mentioned in latest mainline codes and linux-next? > > Peter? > > -- > 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 > -- 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