netdev - Re: [External] Re: [PATCH] mm/memcontrol: Add the drop

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Date:   Tue, 22 Sep 2020 10:51:36 +0100
From:   Chris Down <chris@...isdown.name>
To:     Chunxin Zang <zangchunxin@...edance.com>
Cc:     Michal Hocko <mhocko@...e.com>, Yafang Shao <laoar.shao@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, lizefan@...wei.com,
        Jonathan Corbet <corbet@....net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, kafai@...com,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        andriin@...com, john.fastabend@...il.com, kpsingh@...omium.org,
        Cgroups <cgroups@...r.kernel.org>, linux-doc@...r.kernel.org,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, bpf@...r.kernel.org
Subject: Re: [External] Re: [PATCH] mm/memcontrol: Add the drop_cache
 interface for cgroup v2

Chunxin Zang writes:
>My usecase is that there are two types of services in one server. They
>have difference
>priorities. Type_A has the highest priority, we need to ensure it's
>schedule latency、I/O
>latency、memory enough. Type_B has the lowest priority, we expect it
>will not affect
>Type_A when executed.
>So Type_A could use memory without any limit. Type_B could use memory
>only when the
>memory is absolutely sufficient. But we cannot estimate how much
>memory Type_B should
>use. Because everything is dynamic. So we can't set Type_B's memory.high.
>
>So we want to release the memory of Type_B when global memory is
>insufficient in order
>to ensure the quality of service of Type_A . In the past, we used the
>'force_empty' interface
>of cgroup v1.

This sounds like a perfect use case for memory.low on Type_A, and it's pretty 
much exactly what we invented it for. What's the problem with that?