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

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Message-ID: <20200922124344.GA34296@chrisdown.name>
Date:   Tue, 22 Sep 2020 13:43:44 +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:
>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 :-)