mm: memcontrol: fix NUMA round-robin reclaim at intermediate level

When a cgroup is reclaimed on behalf of a configured limit, reclaim needs
to round-robin through all NUMA nodes that hold pages of the memcg in
question.  However, when assembling the mask of candidate NUMA nodes, the
code only consults the *local* cgroup LRU counters, not the recursive
counters for the entire subtree.  Cgroup limits are frequently configured
against intermediate cgroups that do not have memory on their own LRUs.
In this case, the node mask will always come up empty and reclaim falls
back to scanning only the current node.

If a cgroup subtree has some memory on one node but the processes are
bound to another node afterwards, the limit reclaim will never age or
reclaim that memory anymore.

To fix this, use the recursive LRU counts for a cgroup subtree to
determine which nodes hold memory of that cgroup.

The code has been broken like this forever, so it doesn't seem to be a
problem in practice.  I just noticed it while reviewing the way the LRU
counters are used in general.

Link: http://lkml.kernel.org/r/20190412151507.2769-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2eb2d4ef9b34..2535e54e7989 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1512,13 +1512,13 @@ static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *memcg,
 {
 	struct lruvec *lruvec = mem_cgroup_lruvec(NODE_DATA(nid), memcg);
 
-	if (lruvec_page_state_local(lruvec, NR_INACTIVE_FILE) ||
-	    lruvec_page_state_local(lruvec, NR_ACTIVE_FILE))
+	if (lruvec_page_state(lruvec, NR_INACTIVE_FILE) ||
+	    lruvec_page_state(lruvec, NR_ACTIVE_FILE))
 		return true;
 	if (noswap || !total_swap_pages)
 		return false;
-	if (lruvec_page_state_local(lruvec, NR_INACTIVE_ANON) ||
-	    lruvec_page_state_local(lruvec, NR_ACTIVE_ANON))
+	if (lruvec_page_state(lruvec, NR_INACTIVE_ANON) ||
+	    lruvec_page_state(lruvec, NR_ACTIVE_ANON))
 		return true;
 	return false;