linux-kernel - Re: [RFC-PATCH 1/2] mm: Add __GFP_NO

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Message-ID: <87o8n8hv5p.fsf@nanos.tec.linutronix.de>
Date:   Tue, 18 Aug 2020 16:43:14 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     paulmck@...nel.org, Michal Hocko <mhocko@...e.com>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Joel Fernandes <joel@...lfernandes.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag

On Tue, Aug 18 2020 at 06:53, Paul E. McKenney wrote:
> On Tue, Aug 18, 2020 at 09:43:44AM +0200, Michal Hocko wrote:
>> Thomas had a good point that it doesn't really make much sense to
>> optimize for flooders because that just makes them more effective.
>
> The point is not to make the flooders go faster, but rather for the
> system to be robust in the face of flooders.  Robust as in harder for
> a flooder to OOM the system.
>
> And reducing the number of post-grace-period cache misses makes it
> easier for the callback-invocation-time memory freeing to keep up with
> the flooder, thus avoiding (or at least delaying) the OOM.

Throttling the flooder is incresing robustness far more than reducing
cache misses.

Thanks,

        tglx