linux-kernel - Re: [RFC] mm: memcg: add priority for soft limit reclaiming

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Message-ID: <20190925065248.GF23050@dhcp22.suse.cz>
Date:   Wed, 25 Sep 2019 08:52:48 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Roman Gushchin <guro@...com>, Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC] mm: memcg: add priority for soft limit reclaiming

On Wed 25-09-19 10:35:30, Hillf Danton wrote:
> 
> On Tue, 24 Sep 2019 17:23:35 +0000 from Roman Gushchin
> > 
> > On Tue, Sep 24, 2019 at 03:30:16PM +0200, Michal Hocko wrote:
> > >
> > > But really, make sure you look into the existing feature set that memcg
> > > v2 provides already and come back if you find it unsuitable and we can
> > > move from there. Soft limit reclaim is dead and we should let it RIP.
> > 
> > Can't agree more here.
> > 
> > Cgroup v2 memory protection mechanisms (memory.low/min) should perfectly
> > solve the described problem. If not, let's fix them rather than extend soft
> > reclaim which is already dead.
> > 
> Hehe, IIUC memory.low/min is essentially drawing a line that reclaimers
> would try their best not to cross. Page preemption OTOH is near ten miles
> away from that line though it is now on the shoulder of soft reclaiming.

Dynamic low limit tuning would achieve exactly what you are after - aka
prioritizing some memory consumers over others.
-- 
Michal Hocko
SUSE Labs