linux-kernel - Re: [PATCH v2] mm: introduce memory.min

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Message-ID: <20180424123002.utwbm54mu46q6aqs@esperanza>
Date:   Tue, 24 Apr 2018 15:30:02 +0300
From:   Vladimir Davydov <vdavydov.dev@...il.com>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, kernel-team@...com,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v2] mm: introduce memory.min

Hi Roman,

On Mon, Apr 23, 2018 at 01:36:10PM +0100, Roman Gushchin wrote:
> +  memory.min
> +	A read-write single value file which exists on non-root
> +	cgroups.  The default is "0".
> +
> +	Hard memory protection.  If the memory usage of a cgroup
> +	is within its effective min boundary, the cgroup's memory
> +	won't be reclaimed under any conditions. If there is no
> +	unprotected reclaimable memory available, OOM killer
> +	is invoked.

What will happen if all tasks attached to a cgroup are killed by OOM,
but its memory usage is still within memory.min? Will memory.min be
ignored then?

> +
> +	Effective low boundary is limited by memory.min values of
> +	all ancestor cgroups. If there is memory.min overcommitment
> +	(child cgroup or cgroups are requiring more protected memory
> +	than parent will allow), then each child cgroup will get
> +	the part of parent's protection proportional to its
> +	actual memory usage below memory.min.
> +
> +	Putting more memory than generally available under this
> +	protection is discouraged and may lead to constant OOMs.