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Date: Tue, 19 Dec 2017 09:33:54 -0800
From: Tejun Heo <tj@kernel.org>
Subject: Re: [RFC PATCH] mm: memcontrol: memory+swap accounting for cgroup-v2
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To: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>, Li Zefan <lizefan@huawei.com>, Roman Gushchin <guro@fb.com>, Vladimir Davydov <vdavydov.dev@gmail.com>, Greg Thelen <gthelen@google.com>, Johannes Weiner <hannes@cmpxchg.org>, Hugh Dickins <hughd@google.com>, Andrew Morton <akpm@linux-foundation.org>, Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Cgroups <cgroups@vger.kernel.org>, linux-doc@vger.kernel.org

Hello,

On Tue, Dec 19, 2017 at 09:23:29AM -0800, Shakeel Butt wrote:
> To provide consistent memory usage history using the current
> cgroup-v2's 'swap' interface, an additional metric expressing the
> intersection of memory and swap has to be exposed. Basically memsw is
> the union of memory and swap. So, if that additional metric can be

Exposing anonymous pages with swap backing sounds pretty trivial.

> used to find the union. However for consistent memory limit
> enforcement, I don't think there is an easy way to use current 'swap'
> interface.

Can you please go into details on why this is important?  I get that
you can't do it as easily w/o memsw but I don't understand why this is
a critical feature.  Why is that?

Thanks.

-- 
tejun

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