From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f171.google.com (mail-qk0-f171.google.com [209.85.220.171]) by kanga.kvack.org (Postfix) with ESMTP id 0F4186B0032 for ; Mon, 22 Jun 2015 09:33:07 -0400 (EDT) Received: by qkeo142 with SMTP id o142so83127473qke.1 for ; Mon, 22 Jun 2015 06:33:06 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id b9si9471315qkh.16.2015.06.22.06.33.06 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jun 2015 06:33:06 -0700 (PDT) Message-ID: <55880E86.3000002@redhat.com> Date: Mon, 22 Jun 2015 15:32:54 +0200 From: Jerome Marchand MIME-Version: 1.0 Subject: Re: [PATCHv6 00/36] THP refcounting redesign References: <1433351167-125878-1-git-send-email-kirill.shutemov@linux.intel.com> <558021D9.4050304@redhat.com> <20150622132125.GG7934@node.dhcp.inet.fi> In-Reply-To: <20150622132125.GG7934@node.dhcp.inet.fi> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="DCGagMPAxe45OLNEvMXkFK5Xuw7Nd4cfP" Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Hugh Dickins , 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) --DCGagMPAxe45OLNEvMXkFK5Xuw7Nd4cfP Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 06/22/2015 03:21 PM, Kirill A. Shutemov wrote: > On Tue, Jun 16, 2015 at 03:17:13PM +0200, Jerome Marchand wrote: >> On 06/03/2015 07:05 PM, Kirill A. Shutemov wrote: >>> Hello everybody, >>> >>> Here's new revision of refcounting patchset. Please review and consid= er >>> applying. >>> >>> The goal of patchset is to make refcounting on THP pages cheaper with= >>> simpler semantics and allow the same THP compound page to be mapped w= ith >>> PMD and PTEs. This is required to get reasonable THP-pagecache >>> implementation. >>> >>> With the new refcounting design it's much easier to protect against >>> split_huge_page(): simple reference on a page will make you the deal.= >>> It makes gup_fast() implementation simpler and doesn't require >>> special-case in futex code to handle tail THP pages. >>> >>> It should improve THP utilization over the system since splitting THP= in >>> one process doesn't necessary lead to splitting the page in all other= >>> processes have the page mapped. >>> >>> The patchset drastically lower complexity of get_page()/put_page() >>> codepaths. I encourage people look on this code before-and-after to >>> justify time budget on reviewing this patchset. >>> >>> =3D Changelog =3D >>> >>> v6: >>> - rebase to since-4.0; >>> - optimize mapcount handling: significantely reduce overhead for mo= st >>> common cases. >>> - split pages on migrate_pages(); >>> - remove infrastructure for handling splitting PMDs on all architec= tures; >>> - fix page_mapcount() for hugetlb pages; >>> >> >> Hi Kirill, >> >> I ran some LTP mm tests and hugemmap tests trigger the following: >> >> [ 438.749457] page:ffffea0000df8000 count:2 mapcount:0 mapping: = (null) index:0x0 compound_mapcount: 0 >> [ 438.750089] flags: 0x3ffc0000004001(locked|head) >> [ 438.750089] page dumped because: VM_BUG_ON_PAGE(page_mapped(page)) >=20 > Did you run with original or updated version of patch 27/36? > In original post of v6 there was bug: page_mapped() always returned tru= e. >=20 Indeed! I'll try again with the corrected patch. Thanks, Jerome --DCGagMPAxe45OLNEvMXkFK5Xuw7Nd4cfP 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 iQEcBAEBCAAGBQJViA6KAAoJEHTzHJCtsuoCKpAH/2ETtZ0CobvPY8lHdJMNJRqS UZwKi7NZKytqTyXTjaF81hIifTsEnejvXpifnHWAwdKEM+05bb6URBrmsVqGWbxs s0U6ztNFpnR8SzRW4JIZXRNz5L17SbesWXUV0WCCHMlqYwUgmYKUp8jQh+uygxWu HbkQBdWKshiFJBSX+ks2Qqq8DYNCJkoXs1gFAX/WXt8fiPHhGxQCKyklzTjT/w9P 1h8CANMjlxM/wiW1N3ooNIaxJuhLJ6DJF6hVhO++IdWVYwODIyvCMfFZ/VGqXH65 Qu88zk5nOH+BsA5UbRQc5ytE+X8PfOCWQm78fk8XfpwXtdVi5XyOdOEJX/a/CO4= =FVxM -----END PGP SIGNATURE----- --DCGagMPAxe45OLNEvMXkFK5Xuw7Nd4cfP-- -- 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