linux-kernel - Re: [RFC PATCH] cgroup: introduce proportional protection on memcg

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Message-ID: <Yj26d7eQ2DHXqiE4@dhcp22.suse.cz>
Date:   Fri, 25 Mar 2022 13:49:59 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Zhaoyang Huang <huangzhaoyang@...il.com>
Cc:     Chris Down <chris@...isdown.name>,
        "zhaoyang.huang" <zhaoyang.huang@...soc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        ke wang <ke.wang@...soc.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, cgroups@...r.kernel.org
Subject: Re: [RFC PATCH] cgroup: introduce proportional protection on memcg

On Fri 25-03-22 11:08:00, Zhaoyang Huang wrote:
> On Fri, Mar 25, 2022 at 11:02 AM Zhaoyang Huang <huangzhaoyang@...il.com> wrote:
> >
> > On Thu, Mar 24, 2022 at 10:27 PM Chris Down <chris@...isdown.name> wrote:
> > >
> > > I'm confused by the aims of this patch. We already have proportional reclaim
> > > for memory.min and memory.low, and memory.high is already "proportional" by its
> > > nature to drive memory back down behind the configured threshold.
> > >
> > > Could you please be more clear about what you're trying to achieve and in what
> > > way the existing proportional reclaim mechanisms are insufficient for you?
> 
> sorry for the bad formatting of previous reply, resend it in new format
> 
>  What I am trying to solve is that, the memcg's protection judgment[1]
>  is based on a set of fixed value on current design, while the real
>  scan and reclaim number[2] is based on the proportional min/low on the
>  real memory usage which you mentioned above. Fixed value setting has
>  some constraints as
>  1. It is an experienced value based on observation, which could be inaccurate.
>  2. working load is various from scenarios.
>  3. fixed value from [1] could be against the dynamic cgroup_size in [2].

Could you elaborate some more about those points. I guess providing an
example how you are using the new interface instead would be helpful.
-- 
Michal Hocko
SUSE Labs