linux-kernel - Re: [RFC PATCH 0/2] mm/memcontrol: Finer-grained memory control

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Message-ID: <20190410195443.GL10383@dhcp22.suse.cz>
Date:   Wed, 10 Apr 2019 21:54:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Aaron Lu <aaron.lu@...el.com>
Subject: Re: [RFC PATCH 0/2] mm/memcontrol: Finer-grained memory control

On Wed 10-04-19 15:13:19, Waiman Long wrote:
> The current control mechanism for memory cgroup v2 lumps all the memory
> together irrespective of the type of memory objects. However, there
> are cases where users may have more concern about one type of memory
> usage than the others.
> 
> We have customer request to limit memory consumption on anonymous memory
> only as they said the feature was available in other OSes like Solaris.

Please be more specific about a usecase.

> To allow finer-grained control of memory, this patchset 2 new control
> knobs for memory controller:
>  - memory.subset.list for specifying the type of memory to be under control.
>  - memory.subset.high for the high limit of memory consumption of that
>    memory type.

Please be more specific about the semantic.

I am really skeptical about this feature to be honest, though.

> For simplicity, the limit is not hierarchical and applies to only tasks
> in the local memory cgroup.

This is a no-go to begin with.

> Waiman Long (2):
>   mm/memcontrol: Finer-grained control for subset of allocated memory
>   mm/memcontrol: Add a new MEMCG_SUBSET_HIGH event
> 
>  Documentation/admin-guide/cgroup-v2.rst |  35 +++++++++
>  include/linux/memcontrol.h              |   8 ++
>  mm/memcontrol.c                         | 100 +++++++++++++++++++++++-
>  3 files changed, 142 insertions(+), 1 deletion(-)
> 
> -- 
> 2.18.1

-- 
Michal Hocko
SUSE Labs