Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752678AbaKUGNT (ORCPT ); Fri, 21 Nov 2014 01:13:19 -0500 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:56791 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750876AbaKUGNS (ORCPT ); Fri, 21 Nov 2014 01:13:18 -0500 From: "Aneesh Kumar K.V" To: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli Cc: 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, "Kirill A. Shutemov" Subject: Re: [PATCH 06/19] mm: store mapcount for compound page separate In-Reply-To: <1415198994-15252-7-git-send-email-kirill.shutemov@linux.intel.com> References: <1415198994-15252-1-git-send-email-kirill.shutemov@linux.intel.com> <1415198994-15252-7-git-send-email-kirill.shutemov@linux.intel.com> User-Agent: Notmuch/0.18.2+162~g34d2c62 (http://notmuchmail.org) Emacs/25.0.50.1 (x86_64-pc-linux-gnu) Date: Fri, 21 Nov 2014 11:42:51 +0530 Message-ID: <87h9xt6pzw.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14112106-0033-0000-0000-000000900C1E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "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; } -aneesh -- 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/