Re: [v2 PATCH 2/9] mm: memcontrol: use shrinker_rwsem to protect shrinker_maps allocation

Yang Shi
2020-12-15T20:33:07Z

On Tue, Dec 15, 2020 at 6:10 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Mon, Dec 14, 2020 at 02:37:15PM -0800, Yang Shi wrote:
> > Since memcg_shrinker_map_size just can be changd under holding shrinker_rwsem
> > exclusively, the read side can be protected by holding read lock, so it sounds
> > superfluous to have a dedicated mutex. This should not exacerbate the contention
> > to shrinker_rwsem since just one read side critical section is added.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
>
> Thanks Yang, this is a step in the right direction. It would still be
> nice to also drop memcg_shrinker_map_size and (trivially) derive that
> value from shrinker_nr_max where necessary. It is duplicate state.

Thanks! I will take a further look at it.