From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx197.postini.com [74.125.245.197]) by kanga.kvack.org (Postfix) with SMTP id CA9AA6B0062 for ; Thu, 25 Oct 2012 15:51:23 -0400 (EDT) Date: Thu, 25 Oct 2012 15:51:10 -0400 From: Johannes Weiner Subject: Re: [PATCH v3] mm: thp: Set the accessed flag for old pages on access fault. Message-ID: <20121025195110.GA4771@cmpxchg.org> References: <1351183471-14710-1-git-send-email-will.deacon@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1351183471-14710-1-git-send-email-will.deacon@arm.com> 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 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(). 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