Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756132AbcK2Ip2 (ORCPT ); Tue, 29 Nov 2016 03:45:28 -0500 Received: from mail-wj0-f196.google.com ([209.85.210.196]:35414 "EHLO mail-wj0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753935AbcK2IpT (ORCPT ); Tue, 29 Nov 2016 03:45:19 -0500 Date: Tue, 29 Nov 2016 09:45:16 +0100 From: Michal Hocko To: Naoya Horiguchi Cc: "linux-mm@kvack.org" , "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Dave Hansen , Andrea Arcangeli , Mel Gorman , Vlastimil Babka , Pavel Emelyanov , Zi Yan , Balbir Singh , "linux-kernel@vger.kernel.org" , Naoya Horiguchi Subject: Re: [PATCH v2 04/12] mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION Message-ID: <20161129084516.GB31671@dhcp22.suse.cz> References: <1478561517-4317-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1478561517-4317-5-git-send-email-n-horiguchi@ah.jp.nec.com> <20161128142154.GM14788@dhcp22.suse.cz> <20161129075006.GA15582@hori1.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161129075006.GA15582@hori1.linux.bs1.fc.nec.co.jp> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1156 Lines: 25 On Tue 29-11-16 07:50:06, Naoya Horiguchi wrote: > On Mon, Nov 28, 2016 at 03:21:54PM +0100, Michal Hocko wrote: > > On Tue 08-11-16 08:31:49, Naoya Horiguchi wrote: > > > Introduces CONFIG_ARCH_ENABLE_THP_MIGRATION to limit thp migration > > > functionality to x86_64, which should be safer at the first step. > > > > Please make sure to describe why this has to be arch specific and what > > are arches supposed to provide in order to enable this option. > > OK, the below will be added in the future version: > > Thp migration is an arch-specific feature because it depends on the > arch-dependent behavior of non-present format of page table entry. > What you need to enable this option in other archs are: > - to define arch-specific transformation functions like __pmd_to_swp_entry() > and __swp_entry_to_pmd(), > - to make sure that arch-specific page table walking code can properly handle > !pmd_present case (gup_pmd_range() is a good example), > - (if your archs enables CONFIG_HAVE_ARCH_SOFT_DIRTY,) to define soft dirty > routines like pmd_swp_mksoft_dirty. Thanks this is _much_ better! -- Michal Hocko SUSE Labs