Re: [PATCH 1/7] mm: memcontrol: fix page charging in page replacement

[Michal Hocko]

On Tue 13-04-21 14:51:47, Muchun Song wrote:
> The pages aren't accounted at the root level, so do not charge the page
> to the root memcg in page replacement. Although we do not display the
> value (mem_cgroup_usage) so there shouldn't be any actual problem, but
> there is a WARN_ON_ONCE in the page_counter_cancel(). Who knows if it
> will trigger? So it is better to fix it.
> 
> Signed-off-by: Muchun Song 
> Acked-by: Johannes Weiner 
> Reviewed-by: Shakeel Butt 

Acked-by: Michal Hocko 

> ---
>  mm/memcontrol.c | 8 +---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 64ada9e650a5..f229de925aa5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6806,9 +6806,11 @@ void mem_cgroup_migrate(struct page *oldpage, struct 
> page *newpage)
>   /* Force-charge the new page. The old one will be freed soon */
>   nr_pages = thp_nr_pages(newpage);
>  
> - page_counter_charge(>memory, nr_pages);
> - if (do_memsw_account())
> - page_counter_charge(>memsw, nr_pages);
> + if (!mem_cgroup_is_root(memcg)) {
> + page_counter_charge(>memory, nr_pages);
> + if (do_memsw_account())
> + page_counter_charge(>memsw, nr_pages);
> + }
>  
>   css_get(>css);
>   commit_charge(newpage, memcg);
> -- 
> 2.11.0

-- 
Michal Hocko
SUSE Labs

Re: [PATCH 1/7] mm: memcontrol: fix page charging in page replacement

[Roman Gushchin]

On Tue, Apr 13, 2021 at 02:51:47PM +0800, Muchun Song wrote:
> The pages aren't accounted at the root level, so do not charge the page
> to the root memcg in page replacement. Although we do not display the
> value (mem_cgroup_usage) so there shouldn't be any actual problem, but
> there is a WARN_ON_ONCE in the page_counter_cancel(). Who knows if it
> will trigger? So it is better to fix it.
> 
> Signed-off-by: Muchun Song 
> Acked-by: Johannes Weiner 
> Reviewed-by: Shakeel Butt 

Acked-by: Roman Gushchin 

Thanks!
> ---
>  mm/memcontrol.c | 8 +---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 64ada9e650a5..f229de925aa5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6806,9 +6806,11 @@ void mem_cgroup_migrate(struct page *oldpage, struct 
> page *newpage)
>   /* Force-charge the new page. The old one will be freed soon */
>   nr_pages = thp_nr_pages(newpage);
>  
> - page_counter_charge(>memory, nr_pages);
> - if (do_memsw_account())
> - page_counter_charge(>memsw, nr_pages);
> + if (!mem_cgroup_is_root(memcg)) {
> + page_counter_charge(>memory, nr_pages);
> + if (do_memsw_account())
> + page_counter_charge(>memsw, nr_pages);
> + }
>  
>   css_get(>css);
>   commit_charge(newpage, memcg);
> -- 
> 2.11.0
> 

[PATCH 1/7] mm: memcontrol: fix page charging in page replacement

[Muchun Song]

The pages aren't accounted at the root level, so do not charge the page
to the root memcg in page replacement. Although we do not display the
value (mem_cgroup_usage) so there shouldn't be any actual problem, but
there is a WARN_ON_ONCE in the page_counter_cancel(). Who knows if it
will trigger? So it is better to fix it.

Signed-off-by: Muchun Song 
Acked-by: Johannes Weiner 
Reviewed-by: Shakeel Butt 
---
 mm/memcontrol.c | 8 +---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 64ada9e650a5..f229de925aa5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6806,9 +6806,11 @@ void mem_cgroup_migrate(struct page *oldpage, struct 
page *newpage)
/* Force-charge the new page. The old one will be freed soon */
nr_pages = thp_nr_pages(newpage);
 
-   page_counter_charge(>memory, nr_pages);
-   if (do_memsw_account())
-   page_counter_charge(>memsw, nr_pages);
+   if (!mem_cgroup_is_root(memcg)) {
+   page_counter_charge(>memory, nr_pages);
+   if (do_memsw_account())
+   page_counter_charge(>memsw, nr_pages);
+   }
 
css_get(>css);
commit_charge(newpage, memcg);
-- 
2.11.0