linux-kernel - Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM killer.

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Message-ID: <20180628113942.GD32348@dhcp22.suse.cz>
Date:   Thu, 28 Jun 2018 13:39:42 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM
 killer.

On Wed 27-06-18 07:31:25, Paul E. McKenney wrote:
> On Wed, Jun 27, 2018 at 09:22:07AM +0200, Michal Hocko wrote:
> > On Tue 26-06-18 10:03:45, Paul E. McKenney wrote:
> > [...]
> > > 3.	Something else?
> > 
> > How hard it would be to use a different API than oom notifiers? E.g. a
> > shrinker which just kicks all the pending callbacks if the reclaim
> > priority reaches low values (e.g. 0)?
> 
> Beats me.  What is a shrinker?  ;-)

This is a generich mechanism to reclaim memory that is not on standard
LRU lists. Lwn.net surely has some nice coverage (e.g.
https://lwn.net/Articles/548092/).

> More seriously, could you please point me at an exemplary shrinker
> use case so I can see what is involved?

Well, I am not really sure what is the objective of the oom notifier to
point you to the right direction. IIUC you just want to kick callbacks
to be handled sooner under a heavy memory pressure, right? How is that
achieved? Kick a worker?
-- 
Michal Hocko
SUSE Labs