Re: [PATCH 1/2] mm, memcg: reset memory.low during memcg offlining

Johannes Weiner
2017-07-27T14:35:28Z

CC Andrew - can you route these through the -mm tree please?

On Thu, Jul 27, 2017 at 02:04:27PM +0100, Roman Gushchin wrote:
> A removed memory cgroup with a defined memory.low and some belonging
> pagecache has very low chances to be freed.
>
> If a cgroup has been removed, there is likely no memory pressure inside
> the cgroup, and the pagecache is protected from the external pressure
> by the defined low limit. The cgroup will be freed only after
> the reclaim of all belonging pages. And it will not happen until
> there are any reclaimable memory in the system. That means,
> there is a good chance, that a cold pagecache will reside
> in the memory for an undefined amount of time, wasting
> system resources.
>
> This problem was fixed earlier by commit fa06235b8eb0
> ("cgroup: reset css on destruction"), but it's not a best way
> to do it, as we can't really reset all limits/counters during
> cgroup offlining.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: kernel-team@fb.com
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org

Acked-by: Johannes Weiner <hannes@cmpxchg.org>