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

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Date:   Thu, 27 Jul 2017 10:35:21 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-kernel@...r.kernel.org,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...nel.org>,
        kernel-team@...com, cgroups@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] mm, memcg: reset memory.low during memcg offlining

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@...com>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: kernel-team@...com
> Cc: cgroups@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org

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