From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbeDETEK (ORCPT ); Thu, 5 Apr 2018 15:04:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:49450 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751655AbeDETEJ (ORCPT ); Thu, 5 Apr 2018 15:04:09 -0400 Date: Thu, 5 Apr 2018 21:04:05 +0200 From: Michal Hocko To: Zi Yan Cc: "Kirill A. Shutemov" , Naoya Horiguchi , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm: consider non-anonymous thp as unmovable page Message-ID: <20180405190405.GS6312@dhcp22.suse.cz> References: <20180403083451.GG5501@dhcp22.suse.cz> <20180403105411.hknofkbn6rzs26oz@node.shutemov.name> <20180405085927.GC6312@dhcp22.suse.cz> <20180405122838.6a6b35psizem4tcy@node.shutemov.name> <20180405124830.GJ6312@dhcp22.suse.cz> <20180405134045.7axuun6d7ufobzj4@node.shutemov.name> <20180405150547.GN6312@dhcp22.suse.cz> <20180405155551.wchleyaf4rxooj6m@node.shutemov.name> <20180405160317.GP6312@dhcp22.suse.cz> <7C2DE363-E113-4284-B94F-814F386743DF@sent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7C2DE363-E113-4284-B94F-814F386743DF@sent.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 05-04-18 13:58:43, Zi Yan wrote: > On 5 Apr 2018, at 12:03, Michal Hocko wrote: > > > On Thu 05-04-18 18:55:51, Kirill A. Shutemov wrote: > >> On Thu, Apr 05, 2018 at 05:05:47PM +0200, Michal Hocko wrote: > >>> On Thu 05-04-18 16:40:45, Kirill A. Shutemov wrote: > >>>> On Thu, Apr 05, 2018 at 02:48:30PM +0200, Michal Hocko wrote: > >>> [...] > >>>>> RIght, I confused the two. What is the proper layer to fix that then? > >>>>> rmap_walk_file? > >>>> > >>>> Maybe something like this? Totally untested. > >>> > >>> This looks way too complex. Why cannot we simply split THP page cache > >>> during migration? > >> > >> This way we unify the codepath for archictures that don't support THP > >> migration and shmem THP. > > > > But why? There shouldn't be really nothing to prevent THP (anon or > > shemem) to be migratable. If we cannot migrate it at once we can always > > split it. So why should we add another thp specific handling all over > > the place? > > Then, it would be much easier if your "unclutter thp migration" patches is merged, > plus the patch below: Good point. Except I would prefer a less convoluted condition > diff --git a/mm/migrate.c b/mm/migrate.c > index 60531108021a..b4087aa890f5 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1138,7 +1138,9 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, > int rc = MIGRATEPAGE_SUCCESS; > struct page *newpage; > > - if (!thp_migration_supported() && PageTransHuge(page)) > + if ((!thp_migration_supported() || > + (thp_migration_supported() && !PageAnon(page))) && > + PageTransHuge(page)) > return -ENOMEM; What about this? diff --git a/mm/migrate.c b/mm/migrate.c index 5d0dc7b85f90..cd02e2bdf37c 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1138,7 +1138,11 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, int rc = MIGRATEPAGE_SUCCESS; struct page *newpage; - if (!thp_migration_supported() && PageTransHuge(page)) + /* + * THP pagecache or generally non-migrateable THP need to be split + * up before migration + */ + if (PageTransHuge(page) && (!thp_migration_supported() || !PageAnon(page))) return -ENOMEM; newpage = get_new_page(page, private); -- Michal Hocko SUSE Labs