Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754598AbaKSNCh (ORCPT ); Wed, 19 Nov 2014 08:02:37 -0500 Received: from mta-out1.inet.fi ([62.71.2.203]:38654 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752903AbaKSNCf (ORCPT ); Wed, 19 Nov 2014 08:02:35 -0500 Date: Wed, 19 Nov 2014 15:02:14 +0200 From: "Kirill A. Shutemov" To: Naoya Horiguchi Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH 10/19] thp: PMD splitting without splitting compound page Message-ID: <20141119130214.GB29884@node.dhcp.inet.fi> References: <1415198994-15252-1-git-send-email-kirill.shutemov@linux.intel.com> <1415198994-15252-11-git-send-email-kirill.shutemov@linux.intel.com> <20141119065823.GA16887@hori1.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141119065823.GA16887@hori1.linux.bs1.fc.nec.co.jp> 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 Wed, Nov 19, 2014 at 06:57:47AM +0000, Naoya Horiguchi wrote: > On Wed, Nov 05, 2014 at 04:49:45PM +0200, Kirill A. Shutemov wrote: > > Current split_huge_page() combines two operations: splitting PMDs into > > tables of PTEs and splitting underlying compound page. This patch > > changes split_huge_pmd() implementation to split the given PMD without > > splitting other PMDs this page mapped with or underlying compound page. > > > > In order to do this we have to get rid of tail page refcounting, which > > uses _mapcount of tail pages. Tail page refcounting is needed to be able > > to split THP page at any point: we always know which of tail pages is > > pinned (i.e. by get_user_pages()) and can distribute page count > > correctly. > > > > We can avoid this by allowing split_huge_page() to fail if the compound > > page is pinned. This patch removes all infrastructure for tail page > > refcounting and make split_huge_page() to always return -EBUSY. All > > split_huge_page() users already know how to handle its fail. Proper > > implementation will be added later. > > > > Without tail page refcounting, implementation of split_huge_pmd() is > > pretty straight-forward. > > > > Signed-off-by: Kirill A. Shutemov > > --- > ... > > > diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c > > index 7e70ae968e5f..e4ba17694b6b 100644 > > --- a/arch/powerpc/mm/hugetlbpage.c > > +++ b/arch/powerpc/mm/hugetlbpage.c > > @@ -1022,7 +1022,6 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr, > > { > > unsigned long mask; > > unsigned long pte_end; > > - struct page *head, *page, *tail; > > pte_t pte; > > int refs; > > > > This breaks build of powerpc, so you need keep *head and *page as > you do for other architectures. Yeah. I've already fixed this localy after 0-DAY kernel testing complained. Thanks. -- 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/