lkml.org 
[lkml]   [2008]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] memcg: end migration fix (was [bad page] memcg: another bad page at page migration (2.6.26-rc5-mm3 + patch collection))
KAMEZAWA Hiroyuki wrote:
> Hi, Nishimura-san. thank you for all your help.
>
> I think this one is......hopefully.
>
> ==
>
> In general, mem_cgroup's charge on ANON page is removed when page_remove_rmap()
> is called.
>
> At migration, the newpage is remapped again by remove_migration_ptes(). But
> pte may be already changed (by task exits).
> It is charged at page allocation but have no chance to be uncharged in that
> case because it is never added to rmap.
>
> Handle that corner case in mem_cgroup_end_migration().
>
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
>
> ---
> mm/memcontrol.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> Index: test2-2.6.26-rc5-mm3/mm/memcontrol.c
> ===================================================================
> --- test2-2.6.26-rc5-mm3.orig/mm/memcontrol.c
> +++ test2-2.6.26-rc5-mm3/mm/memcontrol.c
> @@ -747,10 +747,22 @@ int mem_cgroup_prepare_migration(struct
> /* remove redundant charge if migration failed*/
> void mem_cgroup_end_migration(struct page *newpage)
> {
> - /* At success, page->mapping is not NULL and nothing to do. */
> + /*
> + * At success, page->mapping is not NULL.
> + * special rollback care is necessary when
> + * 1. at migration failure. (newpage->mapping is cleared in this case)
> + * 2. the newpage was moved but not remapped again because the task
> + * exits and the newpage is obsolete. In this case, the new page
> + * may be a swapcache. So, we just call mem_cgroup_uncharge_page()
> + * always for avoiding mess. The page_cgroup will be removed if
> + * unnecessary. File cache pages is still on radix-tree. Don't
> + * care it.
> + */
> if (!newpage->mapping)
> __mem_cgroup_uncharge_common(newpage,
> MEM_CGROUP_CHARGE_TYPE_FORCE);
> + else if (PageAnon(newpage))
> + mem_cgroup_uncharge_page(newpage);
> }

Definitely makes sense to me!

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


\
 
 \ /
  Last update: 2008-06-24 09:31    [W:0.034 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site