Re: [PATCH 2/3] mm: memcontrol: do not try to do swap when force empty

From: Shakeel Butt
Date: Wed Jan 02 2019 - 16:46:03 EST

On Wed, Jan 2, 2019 at 12:06 PM Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> wrote:
> The typical usecase of force empty is to try to reclaim as much as
> possible memory before offlining a memcg. Since there should be no
> attached tasks to offlining memcg, the tasks anonymous pages would have
> already been freed or uncharged.

Anon pages can come from tmpfs files as well.

> Even though anonymous pages get
> swapped out, but they still get charged to swap space. So, it sounds
> pointless to do swap for force empty.

I understand that force_empty is typically used before rmdir'ing a
memcg but it might be used differently by some users. We use this
interface to test memory reclaim behavior (anon and file).

Anyways, I am not against changing the behavior, we can adapt
internally but there might be other users using this interface