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From:   Chunxin Zang <zangchunxin@bytedance.com>
Date:   Wed, 23 Sep 2020 10:35:29 +0800
Message-ID: <CAKRVAeNCAVN4qOc57AU_-2dJ8sOT7p6JSO578aD0Seveuv0Rog@mail.gmail.com>
Subject: Re: [External] Re: [PATCH] mm/memcontrol: Add the drop_cache
 interface for cgroup v2
To:     Chris Down <chris@chrisdown.name>
Cc:     Michal Hocko <mhocko@suse.com>, Yafang Shao <laoar.shao@gmail.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, lizefan@huawei.com,
        Jonathan Corbet <corbet@lwn.net>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>, kafai@fb.com,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        andriin@fb.com, john.fastabend@gmail.com, kpsingh@chromium.org,
        Cgroups <cgroups@vger.kernel.org>, linux-doc@vger.kernel.org,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>, bpf@vger.kernel.org
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On Tue, Sep 22, 2020 at 8:43 PM Chris Down <chris@chrisdown.name> wrote:
>
> Chunxin Zang writes:
> >Please forgive me for not being able to understand why setting
> >memory.low for Type_A can solve the problem.
> >In my scene, Type_A is the most important, so I will set 100G to memory.low.
> >But 'memory.low' only takes effect passively when the kernel is
> >reclaiming memory. It means that reclaim Type_B's memory only when
> >Type_A  in alloc memory slow path. This will affect Type_A's
> >performance.
> >We want to reclaim Type_B's memory in advance when A is expected to be busy.
>
> That's what kswapd reclaim is for, so this distinction is meaningless without
> measurements :-)

Thanks for these suggestions, I will give it a try.

Best wishes
Chunxin