[Devel] Re: [PATCH v2 03/13] memcg: Uncharge all kmem when deleting a cgroup.

[Suleiman Souhlal]

On Sun, Mar 11, 2012 at 12:19 AM, Glauber Costa <glommer at parallels.com> wrote:
> On 03/10/2012 12:39 AM, Suleiman Souhlal wrote:
>>
>> Signed-off-by: Suleiman Souhlal<suleiman at google.com>
>> ---
>>  mm/memcontrol.c |   31 ++++++++++++++++++++++++++++++-
>>  1 files changed, 30 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index e6fd558..6fbb438 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -382,6 +382,7 @@ static void mem_cgroup_get(struct mem_cgroup *memcg);
>>  static void mem_cgroup_put(struct mem_cgroup *memcg);
>>  static void memcg_kmem_init(struct mem_cgroup *memcg,
>>      struct mem_cgroup *parent);
>> +static void memcg_kmem_move(struct mem_cgroup *memcg);
>>
>>  static inline bool
>>  mem_cgroup_test_flag(const struct mem_cgroup *memcg, enum memcg_flags
>> flag)
>> @@ -3700,6 +3701,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup
>> *memcg, bool free_all)
>>        int ret;
>>        int node, zid, shrink;
>>        int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
>> +       unsigned long usage;
>>        struct cgroup *cgrp = memcg->css.cgroup;
>>
>>        css_get(&memcg->css);
>> @@ -3719,6 +3721,8 @@ move_account:
>>                /* This is for making all *used* pages to be on LRU. */
>>                lru_add_drain_all();
>>                drain_all_stock_sync(memcg);
>> +               if (!free_all)
>> +                       memcg_kmem_move(memcg);
>
> Any reason we're not moving kmem charges when free_all is set as well?

Because the slab moving code expects to be synchronized with
allocations (and itself). We can't call it when there are still tasks
in the cgroup.

-- Suleiman