On 06.01.2021 01:58, 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>
> ---
> include/linux/memcontrol.h | 1 +
> mm/memcontrol.c | 1 +
> mm/vmscan.c | 29 +++++++++++++++++++++++++++++
> 3 files changed, 31 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 5599082df623..d1e52e916cc2 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1586,6 +1586,7 @@ extern int memcg_alloc_shrinker_info(struct mem_cgroup *memcg);
> extern void memcg_free_shrinker_info(struct mem_cgroup *memcg);
> extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
> int nid, int shrinker_id);
> +extern void memcg_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 126f1fd550c8..19e555675582 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5284,6 +5284,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> page_counter_set_low(&memcg->memory, 0);
>
> memcg_offline_kmem(memcg);
> + memcg_reparent_shrinker_deferred(memcg);
> wb_memcg_offline(memcg);
>
> drain_all_stock(memcg);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index d9795fb0f1c5..71056057d26d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -396,6 +396,35 @@ static long set_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
> return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
> }
>
> +void memcg_reparent_shrinker_deferred(struct mem_cgroup *memcg)
> +{
> + int i, nid;
> + long nr;
> + struct mem_cgroup *parent;
> + struct memcg_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 = rcu_dereference_protected(
> + memcg->nodeinfo[nid]->shrinker_info,
> + true);
> + parent_info = rcu_dereference_protected(
> + parent->nodeinfo[nid]->shrinker_info,
> + true);
Simple assignment can't take such lots of space, we have to do something with that.
Number of these
rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, true)
became too big, and we can't allow every of them takes 3 lines.
We should introduce a short helper to dereferrence this, so we will be able to give
out attention to really difficult logic instead of wasting it on parsing this.
child_info = memcg_shrinker_info(memcg, nid);
or
child_info = memcg_shrinker_info_protected(memcg, nid);
Both of them fit in single line.
struct memcg_shrinker_info *memcg_shrinker_info_protected(
struct mem_cgroup *memcg, int nid)
{
return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
lockdep_assert_held(&shrinker_rwsem));
}
> + 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]);
Why new line is here? In case of you merge it up, it will be even shorter then previous line.
> + }
> + }
> + up_read(&shrinker_rwsem);
> +}
> +
> static bool cgroup_reclaim(struct scan_control *sc)
> {
> return sc->target_mem_cgroup;
>
