From: Glauber Costa <glommer@xxxxxxxxxx>
When a memcg is destroyed, it won't be imediately released until all
objects are gone. This means that if a memcg is restarted with the very
same workload - a very common case, the objects already cached won't be
billed to the new memcg. This is mostly undesirable since a container
can exploit this by restarting itself every time it reaches its limit,
and then coming up again with a fresh new limit.
Since now we have targeted reclaim, I sustain that we should assume that
a memcg that is destroyed should be flushed away. It makes perfect sense
if we assume that a memcg that goes away most likely indicates an
isolated workload that is terminated.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
mm/memcontrol.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 628ea0d..6dadbbe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6441,12 +6441,29 @@ static void memcg_destroy_kmem(struct mem_cgroup *memcg)
static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
{
+ int ret;
if (!memcg_kmem_is_active(memcg))
return;
cancel_work_sync(&memcg->kmemcg_shrink_work);
/*
+ * When a memcg is destroyed, it won't be imediately released until all
+ * objects are gone. This means that if a memcg is restarted with the
+ * very same workload - a very common case, the objects already cached
+ * won't be billed to the new memcg. This is mostly undesirable since a
+ * container can exploit this by restarting itself every time it
+ * reaches its limit, and then coming up again with a fresh new limit.
+ *
+ * Therefore a memcg that is destroyed should be flushed away. It makes
+ * perfect sense if we assume that a memcg that goes away indicates an
+ * isolated workload that is terminated.
+ */
+ do {
+ ret = try_to_free_mem_cgroup_kmem(memcg, GFP_KERNEL);
+ } while (ret);
+
+ /*
* kmem charges can outlive the cgroup. In the case of slab
* pages, for instance, a page contain objects from various
* processes. As we prevent from taking a reference for every
--
1.7.10.4
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