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Subject: Re: [RFC PATCH 0/2] mm/memcontrol: Finer-grained memory control
To:     Kirill Tkhai <ktkhai@virtuozzo.com>, Tejun Heo <tj@kernel.org>,
        Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>
Cc:     linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>,
        Shakeel Butt <shakeelb@google.com>, aryabinin@virtuozzo.com
References: <20190410191321.9527-1-longman@redhat.com>
 <1b6ee304-6176-15a0-c3fa-0b59cdd60085@virtuozzo.com>
From:   Waiman Long <longman@redhat.com>
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Organization: Red Hat
Message-ID: <cea941ed-f401-7380-6e48-622115a02533@redhat.com>
Date:   Thu, 11 Apr 2019 10:55:01 -0400
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On 04/11/2019 10:37 AM, Kirill Tkhai wrote:
> On 10.04.2019 22:13, 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.
>>
>> 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.
>>
>> For simplicity, the limit is not hierarchical and applies to only tasks
>> in the local memory cgroup.
>>
>> 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(-)
> CC Andrey.
>
> In Virtuozzo kernel we have similar functionality for limitation of page cache in a cgroup:
>
> https://github.com/OpenVZ/vzkernel/commit/8ceef5e0c07c7621fcb0e04ccc48a679dfeec4a4

It will be helpful to know the use case where you want to limit page
cache usage. I have anonymous memory in mind when I compose this patch,
but I make the mechanism more generic so that it can apply to other use
cases as well.

Cheers,
Longman