On 1/28/21 12:33 AM, Yang Shi wrote:
> Now shrinker's nr_deferred is per memcg for memcg aware shrinkers, add to parent's
> corresponding nr_deferred when memcg offline.
>
> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
A question somewhat outside of the scope of the series. Should we shrink before
reparenting on memcg offline? Would it make more sense than assume the kmemcg
objects that are still cached are used also by others?
> ---
> include/linux/memcontrol.h | 1 +
> mm/memcontrol.c | 1 +
> mm/vmscan.c | 31 +++++++++++++++++++++++++++++++
> 3 files changed, 33 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index e0384367e07d..fe1375f08881 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1586,6 +1586,7 @@ extern int alloc_shrinker_info(struct mem_cgroup *memcg);
> extern void free_shrinker_info(struct mem_cgroup *memcg);
> extern void set_shrinker_bit(struct mem_cgroup *memcg,
> int nid, int shrinker_id);
> +extern void reparent_shrinker_deferred(struct mem_cgroup *memcg);
> #else
> #define mem_cgroup_sockets_enabled 0
> static inline void mem_cgroup_sk_alloc(struct sock *sk) { };
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f64ad0d044d9..21f36b73f36a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5282,6 +5282,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> page_counter_set_low(&memcg->memory, 0);
>
> memcg_offline_kmem(memcg);
> + reparent_shrinker_deferred(memcg);
> wb_memcg_offline(memcg);
>
> drain_all_stock(memcg);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 0373d7619d7b..55ad91a26ba3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -386,6 +386,37 @@ static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
> return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
> }
>
> +static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
> + int nid)
> +{
> + return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
> + lockdep_is_held(&shrinker_rwsem));
> +}
> +
> +void reparent_shrinker_deferred(struct mem_cgroup *memcg)
> +{
> + int i, nid;
> + long nr;
> + struct mem_cgroup *parent;
> + struct shrinker_info *child_info, *parent_info;
> +
> + parent = parent_mem_cgroup(memcg);
> + if (!parent)
> + parent = root_mem_cgroup;
> +
> + /* Prevent from concurrent shrinker_info expand */
> + down_read(&shrinker_rwsem);
> + for_each_node(nid) {
> + child_info = shrinker_info_protected(memcg, nid);
> + parent_info = shrinker_info_protected(parent, nid);
> + for (i = 0; i < shrinker_nr_max; i++) {
> + nr = atomic_long_read(&child_info->nr_deferred[i]);
> + atomic_long_add(nr, &parent_info->nr_deferred[i]);
> + }
> + }
> + up_read(&shrinker_rwsem);
> +}
> +
> static bool cgroup_reclaim(struct scan_control *sc)
> {
> return sc->target_mem_cgroup;
>
