From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 128E68E00A4 for ; Tue, 25 Sep 2018 17:11:27 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id d28-v6so15889edb.17 for ; Tue, 25 Sep 2018 14:11:27 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q25-v6si30177edi.5.2018.09.25.14.11.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Sep 2018 14:11:25 -0700 (PDT) Date: Tue, 25 Sep 2018 23:11:23 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: Disable movable allocation for TRANSHUGE pages Message-ID: <20180925211123.GZ18685@dhcp22.suse.cz> References: <1537860333-28416-1-git-send-email-amhetre@nvidia.com> <20180925115153.z5b5ekijf5jzhzmn@kshutemo-mobl1> <20180925183019.GB22630@dhcp22.suse.cz> <20180925210001.j4olzx3fru4jpfys@kshutemo-mobl1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180925210001.j4olzx3fru4jpfys@kshutemo-mobl1> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Ashish Mhetre , linux-mm@kvack.org, akpm@linux-foundation.org, vdumpa@nvidia.com, Snikam@nvidia.com On Wed 26-09-18 00:00:02, Kirill A. Shutemov wrote: > On Tue, Sep 25, 2018 at 08:30:19PM +0200, Michal Hocko wrote: > > On Tue 25-09-18 14:51:53, Kirill A. Shutemov wrote: > > > On Tue, Sep 25, 2018 at 12:55:33PM +0530, Ashish Mhetre wrote: > > > > TRANSHUGE pages have no migration support. > > > > > > Transparent pages have migration support since v4.14. > > > > This is true but not for all architectures AFAICS. In fact git grep > > suggests that only x86 supports the migration. So unless I am missing > > something the patch has some merit. > > THP pages are movable from the beginning. Before 4.14, the cost of > migration was THP split. From my PoV __GFP_MOVABLE is justified and we > should keep it there. A very good point! I haven't really looked closer to what happens in the cma/migration code when the migration is not supported. As you've said THP migt be split into 4kB pages and those are migrateable by definition. So I take back my proposal and if this doesn't work properly now then it should really be handled by splitting up the thp. Thanks and sorry I've missed this! -- Michal Hocko SUSE Labs