linux-kernel - Re: [PATCH] mm/memcontrol: Add the drop

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Message-ID: <20200922100152.GW12990@dhcp22.suse.cz>
Date:   Tue, 22 Sep 2020 12:01:52 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     zangchunxin@...edance.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: [PATCH] mm/memcontrol: Add the drop_cache interface for cgroup v2

On Tue 22-09-20 16:06:31, Yafang Shao wrote:
> On Tue, Sep 22, 2020 at 3:27 PM Michal Hocko <mhocko@...e.com> wrote:
[...]
> > What is the latency triggered by the memory reclaim? It should be mostly
> > a clean page cache right as drop_caches only drops clean pages. Or is
> > this more about [id]cache? Do you have any profiles where is the time
> > spent?
> >
> 
> Yes, we have analyzed the issues in the direct reclaim, but that is
> not the point.

Are those fixed?

> The point is that each case may take us several days to analyze, while
> the user can't wait, so they will use drop_caches to workaround it
> until we find the solution.

As I've said there are several options to achieve an immediate action.
Careful resource domains configuration will certainly help with that.
-- 
Michal Hocko
SUSE Labs