diff mbox series

[RFC,v2,01/18] mm: memcontrol: fix page charging in page replacement

Message ID 20210409122959.82264-2-songmuchun@bytedance.com (mailing list archive)
State New, archived
Headers show
Series Use obj_cgroup APIs to charge the LRU pages | expand

Commit Message

Muchun Song April 9, 2021, 12:29 p.m. UTC 
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 <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Comments

Shakeel Butt April 10, 2021, 5:44 p.m. UTC | #1 
On Fri, Apr 9, 2021 at 5:32 AM Muchun Song <songmuchun@bytedance.com> 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 <songmuchun@bytedance.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Shakeel Butt <shakeelb@google.com>
diff mbox series

Patch

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(&memcg->memory, nr_pages);
-	if (do_memsw_account())
-		page_counter_charge(&memcg->memsw, nr_pages);
+	if (!mem_cgroup_is_root(memcg)) {
+		page_counter_charge(&memcg->memory, nr_pages);
+		if (do_memsw_account())
+			page_counter_charge(&memcg->memsw, nr_pages);
+	}
 
 	css_get(&memcg->css);
 	commit_charge(newpage, memcg);