From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f42.google.com (mail-qg0-f42.google.com [209.85.192.42]) by kanga.kvack.org (Postfix) with ESMTP id 09C816B0254 for ; Fri, 31 Jul 2015 10:51:53 -0400 (EDT) Received: by qged69 with SMTP id d69so47196071qge.0 for ; Fri, 31 Jul 2015 07:51:52 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id q42si6026855qkh.117.2015.07.31.07.51.52 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 Jul 2015 07:51:52 -0700 (PDT) Message-ID: <55BB8B81.5030904@redhat.com> Date: Fri, 31 Jul 2015 16:51:45 +0200 From: Jerome Marchand MIME-Version: 1.0 Subject: Re: [PATCHv9 13/36] mm: drop tail page refcounting References: <1437402069-105900-1-git-send-email-kirill.shutemov@linux.intel.com> <1437402069-105900-14-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1437402069-105900-14-git-send-email-kirill.shutemov@linux.intel.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="xx3CWnb6KwdlmaRsBXgsoBIagJpT3B1cd" Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Hugh Dickins Cc: Dave Hansen , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Sasha Levin , linux-kernel@vger.kernel.org, linux-mm@kvack.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --xx3CWnb6KwdlmaRsBXgsoBIagJpT3B1cd Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 07/20/2015 04:20 PM, Kirill A. Shutemov wrote: > Tail page refcounting is utterly complicated and painful to support. >=20 > It uses ->_mapcount on tail pages to store how many times this page is > pinned. get_page() bumps ->_mapcount on tail page in addition to > ->_count on head. This information is required by split_huge_page() to > be able to distribute pins from head of compound page to tails during > the split. >=20 > We will need ->_mapcount to account PTE mappings of subpages of the > compound page. We eliminate need in current meaning of ->_mapcount in > tail pages by forbidding split entirely if the page is pinned. >=20 > The only user of tail page refcounting is THP which is marked BROKEN fo= r > now. >=20 > Let's drop all this mess. It makes get_page() and put_page() much > simpler. >=20 > Signed-off-by: Kirill A. Shutemov > Tested-by: Sasha Levin > Tested-by: Aneesh Kumar K.V > Acked-by: Vlastimil Babka Acked-by: Jerome Marchand > --- > arch/mips/mm/gup.c | 4 - > arch/powerpc/mm/hugetlbpage.c | 13 +- > arch/s390/mm/gup.c | 13 +- > arch/sparc/mm/gup.c | 14 +-- > arch/x86/mm/gup.c | 4 - > include/linux/mm.h | 47 ++------ > include/linux/mm_types.h | 17 +-- > mm/gup.c | 34 +----- > mm/huge_memory.c | 41 +------ > mm/hugetlb.c | 2 +- > mm/internal.h | 44 ------- > mm/swap.c | 273 +++-------------------------------= -------- > 12 files changed, 40 insertions(+), 466 deletions(-) >=20 --xx3CWnb6KwdlmaRsBXgsoBIagJpT3B1cd Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJVu4uBAAoJEHTzHJCtsuoCoSMH/RC/90otzHeGxEJbQVU91ffO ESX1zg2XbiTYFiTlYlwikb/s5AjMg9WvF6UI8THl1eY04b2ybIvzJjAK3QkdT0YA RixbpOejf9HamG4GtSx5HjUEi/q7n95GPA/o6yvdNLKu+nYcAQXkysvuqy191B8r qD+vKamNg88XkE9NG1uFloPko/zu7PawMzKluVyL7EQpfKGD5oEKSMzsEv3X/n6I N7SqdrW4E+XLMIpv1JwSbNlnEySzMHxgVcDA1sXlHFy+PEVQSAvgpghcptveXtO2 wc3JdH+YXKNpbyWqG7mZGKnnkDxf1BVVqK3ujdc9wlzaYsvpRQ1zW+MtprUMuqY= =ABSG -----END PGP SIGNATURE----- --xx3CWnb6KwdlmaRsBXgsoBIagJpT3B1cd-- -- 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