[PATCH 10/11] memcg: allow a memcg with kmem charges to be destructed.
From: Glauber Costa <hidden>
Date: 2012-06-25 14:18:42
Also in:
cgroups, lkml
Subsystem:
control group - memory resource controller (memcg), memory management, the rest · Maintainers:
Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt, Andrew Morton, Linus Torvalds
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 <redacted> CC: Christoph Lameter <redacted> CC: Pekka Enberg <redacted> CC: Michal Hocko <redacted> CC: Kamezawa Hiroyuki <redacted> CC: Johannes Weiner <hannes@cmpxchg.org> CC: Suleiman Souhlal <redacted> --- 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); } #else static void disarm_kmem_keys(struct mem_cgroup *memcg)
@@ -3838,6 +3843,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all) int node, zid, shrink; int nr_retries = MEM_CGROUP_RECLAIM_RETRIES; struct cgroup *cgrp = memcg->css.cgroup; + u64 usage; css_get(&memcg->css);
@@ -3877,8 +3883,10 @@ move_account: if (ret == -ENOMEM) goto try_to_free; cond_resched(); + usage = res_counter_read_u64(&memcg->res, RES_USAGE) - + res_counter_read_u64(&memcg->kmem, RES_USAGE); /* "ret" should also be checked to ensure all lists are empty. */ - } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0 || ret); + } while (usage > 0 || ret); out: css_put(&memcg->css); return ret;
--
1.7.10.2
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