Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757986AbaKUMDa (ORCPT ); Fri, 21 Nov 2014 07:03:30 -0500 Received: from mta-out1.inet.fi ([62.71.2.203]:33190 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbaKUMD2 (ORCPT ); Fri, 21 Nov 2014 07:03:28 -0500 Date: Fri, 21 Nov 2014 14:02:55 +0200 From: "Kirill A. Shutemov" To: "Aneesh Kumar K.V" Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , Johannes Weiner , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 06/19] mm: store mapcount for compound page separate Message-ID: <20141121120255.GC16647@node.dhcp.inet.fi> References: <1415198994-15252-1-git-send-email-kirill.shutemov@linux.intel.com> <1415198994-15252-7-git-send-email-kirill.shutemov@linux.intel.com> <87h9xt6pzw.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h9xt6pzw.fsf@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 21, 2014 at 11:42:51AM +0530, Aneesh Kumar K.V wrote: > "Kirill A. Shutemov" writes: > > > We're going to allow mapping of individual 4k pages of THP compound and > > we need a cheap way to find out how many time the compound page is > > mapped with PMD -- compound_mapcount() does this. > > > > page_mapcount() counts both: PTE and PMD mappings of the page. > > > > Signed-off-by: Kirill A. Shutemov > > --- > > include/linux/mm.h | 17 +++++++++++++++-- > > include/linux/rmap.h | 4 ++-- > > mm/huge_memory.c | 23 ++++++++++++++--------- > > mm/hugetlb.c | 4 ++-- > > mm/memory.c | 2 +- > > mm/migrate.c | 2 +- > > mm/page_alloc.c | 13 ++++++++++--- > > mm/rmap.c | 50 +++++++++++++++++++++++++++++++++++++++++++------- > > 8 files changed, 88 insertions(+), 27 deletions(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 1825c468f158..aef03acff228 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -435,6 +435,19 @@ static inline struct page *compound_head(struct page *page) > > return page; > > } > > > > +static inline atomic_t *compound_mapcount_ptr(struct page *page) > > +{ > > + return (atomic_t *)&page[1].mapping; > > +} > > + > > +static inline int compound_mapcount(struct page *page) > > +{ > > + if (!PageCompound(page)) > > + return 0; > > + page = compound_head(page); > > + return atomic_read(compound_mapcount_ptr(page)) + 1; > > +} > > > How about > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 6e0b286649f1..59c9cf3d8510 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -46,6 +46,11 @@ struct page { > unsigned long flags; /* Atomic flags, some possibly > * updated asynchronously */ > union { > + /* > + * For THP we use this to track the compound > + * page mapcount. > + */ > + atomic_t _compound_mapcount; > struct address_space *mapping; /* If low bit clear, points to > * inode address_space, or NULL. > * If page mapped as anonymous > > and > > static inline atomic_t *compound_mapcount_ptr(struct page *page) > { > return (atomic_t *)&page[1]._compound_mapcount; > } Cast is redundant ;) See answer to Christoph. -- 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/