Re: [PATCH 2/8] mm: memcontrol: remove double kmem page_counter init

Michal Hocko
2015-12-10T12:40:23Z

On Tue 08-12-15 13:34:19, Johannes Weiner wrote:
> The kmem page_counter's limit is initialized to PAGE_COUNTER_MAX
> inside mem_cgroup_css_online(). There is no need to repeat this
> from memcg_propagate_kmem().
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memcontrol.c | 24 ++++++++++--------------
> 1 file changed, 10 insertions(+), 14 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index eda8d43..02167db 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2840,8 +2840,7 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
> }
>
> #ifdef CONFIG_MEMCG_KMEM
> -static int memcg_activate_kmem(struct mem_cgroup *memcg,
> - unsigned long nr_pages)
> +static int memcg_activate_kmem(struct mem_cgroup *memcg)
> {
> int err = 0;
> int memcg_id;
> @@ -2876,13 +2875,6 @@ static int memcg_activate_kmem(struct mem_cgroup *memcg,
> goto out;
> }
>
> - /*
> - * We couldn't have accounted to this cgroup, because it hasn't got
> - * activated yet, so this should succeed.
> - */
> - err = page_counter_limit(&memcg->kmem, nr_pages);
> - VM_BUG_ON(err);
> -
> static_branch_inc(&memcg_kmem_enabled_key);
> /*
> * A memory cgroup is considered kmem-active as soon as it gets
> @@ -2903,10 +2895,14 @@ static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
> int ret;
>
> mutex_lock(&memcg_limit_mutex);
> - if (!memcg_kmem_is_active(memcg))
> - ret = memcg_activate_kmem(memcg, limit);
> - else
> - ret = page_counter_limit(&memcg->kmem, limit);
> + /* Top-level cgroup doesn't propagate from root */
> + if (!memcg_kmem_is_active(memcg)) {
> + ret = memcg_activate_kmem(memcg);
> + if (ret)
> + goto out;
> + }
> + ret = page_counter_limit(&memcg->kmem, limit);
> +out:
> mutex_unlock(&memcg_limit_mutex);
> return ret;
> }
> @@ -2925,7 +2921,7 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
> * after this point, because it has at least one child already.
> */
> if (memcg_kmem_is_active(parent))
> - ret = memcg_activate_kmem(memcg, PAGE_COUNTER_MAX);
> + ret = memcg_activate_kmem(memcg);
> mutex_unlock(&memcg_limit_mutex);
> return ret;
> }
> --
> 2.6.3

--
Michal Hocko
SUSE Labs