From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933454AbbFVNWI (ORCPT ); Mon, 22 Jun 2015 09:22:08 -0400 Received: from mta-out1.inet.fi ([62.71.2.229]:34559 "EHLO johanna3.rokki.sonera.fi" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754011AbbFVNV6 (ORCPT ); Mon, 22 Jun 2015 09:21:58 -0400 RazorGate-KAS: Rate: 5 RazorGate-KAS: {RECEIVED: dynamic ip detected} RazorGate-KAS: Envelope from: RazorGate-KAS: Version: 5.5.3 RazorGate-KAS: LuaCore: 80 2014-11-10_18-01-23 260f8afb9361da3c7edfd3a8e3a4ca908191ad29 RazorGate-KAS: Method: none RazorGate-KAS: Lua profiles 69136 [Nov 12 2014] RazorGate-KAS: Status: not_detected Date: Mon, 22 Jun 2015 16:21:25 +0300 From: "Kirill A. Shutemov" To: Jerome Marchand 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 Subject: Re: [PATCHv6 00/36] THP refcounting redesign Message-ID: <20150622132125.GG7934@node.dhcp.inet.fi> References: <1433351167-125878-1-git-send-email-kirill.shutemov@linux.intel.com> <558021D9.4050304@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <558021D9.4050304@redhat.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 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 consider > > 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 with > > 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. > > > > = Changelog = > > > > v6: > > - rebase to since-4.0; > > - optimize mapcount handling: significantely reduce overhead for most > > common cases. > > - split pages on migrate_pages(); > > - remove infrastructure for handling splitting PMDs on all architectures; > > - 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)) Did you run with original or updated version of patch 27/36? In original post of v6 there was bug: page_mapped() always returned true. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/