[RFC PATCH 1/2] memcg: fix memory.low

Greg Thelen
2018-04-22T20:26:51Z

When targeting reclaim to a memcg, protect that memcg from reclaim is
memory consumption of any level is below respective memory.low.

Signed-off-by: Greg Thelen <gthelen@google.com>
---
mm/memcontrol.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 670e99b68aa6..9668f620203a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5341,8 +5341,8 @@ struct cgroup_subsys memory_cgrp_subsys = {
* @root: the top ancestor of the sub-tree being checked
* @memcg: the memory cgroup to check
*
- * Returns %true if memory consumption of @memcg, and that of all
- * ancestors up to (but not including) @root, is below the normal range.
+ * Returns %true if memory consumption of @memcg, or any of its ancestors
+ * up to (but not including) @root, is below the normal range.
*
* @root is exclusive; it is never low when looked at directly and isn't
* checked when traversing the hierarchy.
@@ -5379,12 +5379,12 @@ bool mem_cgroup_low(struct mem_cgroup *root, struct mem_cgroup *memcg)
if (memcg == root)
return false;

+ /* If any level is under, then protect @memcg from reclaim */
for (; memcg != root; memcg = parent_mem_cgroup(memcg)) {
- if (page_counter_read(&memcg->memory) >= memcg->low)
- return false;
+ if (page_counter_read(&memcg->memory) <= memcg->low)
+ return true; /* protect from reclaim */
}
-
- return true;
+ return false; /* not protected from reclaim */
}

/**
--
2.17.0.484.g0c8726318c-goog