Re: [PATCH] memcg: avoid refill_stock for root memcg

[Johannes Weiner]

On Wed, Mar 12, 2025 at 10:48:12PM -0700, Shakeel Butt wrote:
> We never charge the page counters of root memcg, so there is no need to
> put root memcg in the memcg stock. At the moment, refill_stock() can be
> called from try_charge_memcg(), obj_cgroup_uncharge_pages() and
> mem_cgroup_uncharge_skmem().
> 
> The try_charge_memcg() and mem_cgroup_uncharge_skmem() are never called
> with root memcg, so those are fine. However obj_cgroup_uncharge_pages()
> can potentially call refill_stock() with root memcg if the objcg object
> has been reparented over to the root memcg. Let's just avoid
> refill_stock() from obj_cgroup_uncharge_pages() for root memcg.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>