Re: [PATCH 10/11] memcg: allow a memcg with kmem charges to be destructed.
From: Glauber Costa
Date: Mon Jun 25 2012 - 18:28:39 EST
On 06/25/2012 10:34 PM, Tejun Heo wrote:
On Mon, Jun 25, 2012 at 06:15:27PM +0400, Glauber Costa wrote:
Because the ultimate goal of the kmem tracking in memcg is to
track slab pages as well, we can't guarantee that we'll always
be able to point a page to a particular process, and migrate
the charges along with it - since in the common case, a page
will contain data belonging to multiple processes.
Because of that, when we destroy a memcg, we only make sure
the destruction will succeed by discounting the kmem charges
from the user charges when we try to empty the cgroup.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
---
mm/memcontrol.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a6a440b..bb9b6fe 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -598,6 +598,11 @@ static void disarm_kmem_keys(struct mem_cgroup *memcg)
{
if (test_bit(KMEM_ACCOUNTED_THIS, &memcg->kmem_accounted))
static_key_slow_dec(&mem_cgroup_kmem_enabled_key);
+ /*
+ * This check can't live in kmem destruction function,
+ * since the charges will outlive the cgroup
+ */
+ BUG_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
WARN_ON() please. Misaccounted kernel usually is better than dead
kernel.
You're absolutely right, will change.
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