From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754513Ab2AYABw (ORCPT ); Tue, 24 Jan 2012 19:01:52 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:52086 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754453Ab2AYABt (ORCPT ); Tue, 24 Jan 2012 19:01:49 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 25 Jan 2012 09:00:25 +0900 From: KAMEZAWA Hiroyuki To: Michal Hocko Cc: Johannes Weiner , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" , Hugh Dickins , Ying Han Subject: Re: [PATCH v4] memcg: remove PCG_CACHE page_cgroup flag Message-Id: <20120125090025.6d24cd0f.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20120124180842.GA18372@tiehlicka.suse.cz> References: <20120119181711.8d697a6b.kamezawa.hiroyu@jp.fujitsu.com> <20120120122658.1b14b512.kamezawa.hiroyu@jp.fujitsu.com> <20120120084545.GC9655@tiehlicka.suse.cz> <20120124121636.115f1cf0.kamezawa.hiroyu@jp.fujitsu.com> <20120124111644.GE1660@cmpxchg.org> <20120124145411.GF1660@cmpxchg.org> <20120124160140.GH26289@tiehlicka.suse.cz> <20120124164449.GH1660@cmpxchg.org> <20120124172308.GI26289@tiehlicka.suse.cz> <20120124180842.GA18372@tiehlicka.suse.cz> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.1.1 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 24 Jan 2012 19:09:47 +0100 Michal Hocko wrote: > On Tue 24-01-12 18:23:08, Michal Hocko wrote: > > On Tue 24-01-12 17:44:49, Johannes Weiner wrote: > > > On Tue, Jan 24, 2012 at 05:01:40PM +0100, Michal Hocko wrote: > > > > On Tue 24-01-12 15:54:11, Johannes Weiner wrote: > > > > > Hold on, I think this patch is still not complete: end_migration() > > > > > directly uses __mem_cgroup_uncharge_common() with the FORCE charge > > > > > type. This will uncharge all migrated anon pages as cache, when it > > > > > should decide based on PageAnon(used), which is the page where > > > > > ->mapping is intact after migration. > > > > > > > > You are right, I've missed that one as well. Anyway > > > > MEM_CGROUP_CHARGE_TYPE_FORCE is used only in mem_cgroup_end_migration > > > > these days and it got out of sync with its documentation (used by > > > > force_empty) quite some time ago (f817ed48). What about something like > > > > the following on top of the previous patch? > > > > --- > > > > Should be foldet into the previous patch with the updated changelog: > > > > > > > > Mapping of the unused page is not touched during migration (see > > > > > > used one, not unused. unused->mapping is globbered during migration. > > > > Yes, you are right: > > Sorry I haven't sent the most recent update. Here we go: > --- > Should be folded into the previous patch with the updated changelog: > Thanks, I'll fold this into v5. -Kame > Mapping of the used page is not touched during migration (see > page_remove_rmap) so we can rely on it and push the correct charge type > down to __mem_cgroup_uncharge_common from end_migration for unused page. > The force flag was misleading was abused for skipping the needless > page_mapped() / PageCgroupMigration() check, as we know the unused page > is no longer mapped and cleared the migration flag just a few lines > up. But doing the checks is no biggie and it's not worth adding another > flag just to skip them. But I guess this should be mentioned in the > changelog. > --- > mm/memcontrol.c | 9 +++++++-- > 1 files changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 4d655ee..869744a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3195,6 +3195,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, > { > struct page *used, *unused; > struct page_cgroup *pc; > + bool anon; > > if (!memcg) > return; > @@ -3207,6 +3208,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, > used = newpage; > unused = oldpage; > } > + > /* > * We disallowed uncharge of pages under migration because mapcount > * of the page goes down to zero, temporarly. > @@ -3217,7 +3219,10 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, > ClearPageCgroupMigration(pc); > unlock_page_cgroup(pc); > > - __mem_cgroup_uncharge_common(unused, MEM_CGROUP_CHARGE_TYPE_FORCE); > + anon = PageAnon(used); > + __mem_cgroup_uncharge_common(unused, > + anon ? MEM_CGROUP_CHARGE_TYPE_MAPPED > + : MEM_CGROUP_CHARGE_TYPE_CACHE); > > /* > * If a page is a file cache, radix-tree replacement is very atomic > @@ -3227,7 +3232,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg, > * and USED bit check in mem_cgroup_uncharge_page() will do enough > * check. (see prepare_charge() also) > */ > - if (PageAnon(used)) > + if (anon) > mem_cgroup_uncharge_page(used); > /* > * At migration, we may charge account against cgroup which has no > -- > 1.7.8.3 > > -- > Michal Hocko > SUSE Labs > SUSE LINUX s.r.o. > Lihovarska 1060/12 > 190 00 Praha 9 > Czech Republic >