On Tue, 24 Jan 2012 19:09:47 +0100
Michal Hocko <mhocko@xxxxxxx> 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
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>