From: Muchun Song songmuchun@bytedance.com Subject: mm: memcg/slab: fix root memcg vmstats
If we reparent the slab objects to the root memcg, when we free the slab object, we need to update the per-memcg vmstats to keep it correct for the root memcg. Now this at least affects the vmstat of NR_KERNEL_STACK_KB for !CONFIG_VMAP_STACK when the thread stack size is smaller than the PAGE_SIZE.
David said: "I assume that without this fix that the root memcg's vmstat would always be inflated if we reparented."
Link: https://lkml.kernel.org/r/20201110031015.15715-1-songmuchun@bytedance.com Fixes: ec9f02384f60 ("mm: workingset: fix vmstat counters for shadow nodes") Signed-off-by: Muchun Song songmuchun@bytedance.com Acked-by: Roman Gushchin guro@fb.com Reviewed-by: Shakeel Butt shakeelb@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: David Rientjes rientjes@google.com Cc: Michal Hocko mhocko@kernel.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Christopher Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Roman Gushchin guro@fb.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Yafang Shao laoar.shao@gmail.com Cc: Chris Down chris@chrisdown.name Cc: stable@vger.kernel.org [5.3+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/memcontrol.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c~mm-memcg-slab-fix-root-memcg-vmstats +++ a/mm/memcontrol.c @@ -867,8 +867,13 @@ void __mod_lruvec_slab_state(void *p, en rcu_read_lock(); memcg = mem_cgroup_from_obj(p);
- /* Untracked pages have no memcg, no lruvec. Update only the node */ - if (!memcg || memcg == root_mem_cgroup) { + /* + * Untracked pages have no memcg, no lruvec. Update only the + * node. If we reparent the slab objects to the root memcg, + * when we free the slab object, we need to update the per-memcg + * vmstats to keep it correct for the root memcg. + */ + if (!memcg) { __mod_node_page_state(pgdat, idx, val); } else { lruvec = mem_cgroup_lruvec(memcg, pgdat); _