From: Michal Hocko <mhocko@suse.cz>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>
Subject: Re: [PATCH v4] memcg: remove PCG_CACHE page_cgroup flag
Date: Tue, 24 Jan 2012 18:23:08 +0100 [thread overview]
Message-ID: <20120124172308.GI26289@tiehlicka.suse.cz> (raw)
In-Reply-To: <20120124164449.GH1660@cmpxchg.org>
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:
---
Should be foldet into the previous patch with the updated changelog:
Mapping of the unused 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.
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.
[hannes@cmpxchg.org: fix for end_migration with clarification]
---
mm/memcontrol.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4d655ee..6a8cc56 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
--
1.7.8.3
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
next prev parent reply other threads:[~2012-01-24 17:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-19 9:17 [PATCH] memcg: remove PCG_CACHE page_cgroup flag KAMEZAWA Hiroyuki
2012-01-19 13:30 ` Johannes Weiner
2012-01-19 23:55 ` KAMEZAWA Hiroyuki
2012-01-19 13:43 ` Michal Hocko
2012-01-19 23:56 ` KAMEZAWA Hiroyuki
2012-01-20 3:26 ` [PATCH v3] " KAMEZAWA Hiroyuki
2012-01-20 8:45 ` Michal Hocko
2012-01-24 3:16 ` [PATCH v4] " KAMEZAWA Hiroyuki
2012-01-24 8:56 ` Michal Hocko
2012-01-24 11:16 ` Johannes Weiner
2012-01-24 14:54 ` Johannes Weiner
2012-01-24 16:01 ` Michal Hocko
2012-01-24 16:44 ` Johannes Weiner
2012-01-24 17:23 ` Michal Hocko [this message]
2012-01-24 18:09 ` Michal Hocko
2012-01-25 0:00 ` KAMEZAWA Hiroyuki
2012-01-25 5:41 ` [PATCH v5] " KAMEZAWA Hiroyuki
2012-01-25 12:24 ` Michal Hocko
2012-01-25 13:36 ` Johannes Weiner
2012-01-20 10:33 ` [PATCH v3] " Johannes Weiner
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