Messages in this thread | | | Date | Tue, 26 Jun 2012 02:25:46 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH 10/11] memcg: allow a memcg with kmem charges to be destructed. |
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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@parallels.com> >> CC: Christoph Lameter <cl@linux.com> >> CC: Pekka Enberg <penberg@cs.helsinki.fi> >> CC: Michal Hocko <mhocko@suse.cz> >> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> >> CC: Johannes Weiner <hannes@cmpxchg.org> >> CC: Suleiman Souhlal <suleiman@google.com> >> --- >> 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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