On Wed, Jan 6, 2021 at 3:35 AM Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote:
>
> 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));
> }
Thanks for the suggestion, it makes sense to me. Will incorporate it in v4.
>
>
> > + 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.
Just keep in 80 lines. We could relax it.
>
> > + }
> > + }
> > + up_read(&shrinker_rwsem);
> > +}
> > +
> > static bool cgroup_reclaim(struct scan_control *sc)
> > {
> > return sc->target_mem_cgroup;
> >
>
>
