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

[Johannes Weiner]

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@xxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

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.