linux-kernel - Re: [patch v2 2/2] mm, oom: avoid reaping only for mm's with blockable invalidate callbacks

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Date:   Fri, 15 Dec 2017 13:46:50 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Oded Gabbay <oded.gabbay@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Joerg Roedel <joro@...tes.org>,
        Doug Ledford <dledford@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Dimitri Sivanich <sivanich@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v2 2/2] mm, oom: avoid reaping only for mm's with blockable
 invalidate callbacks

On Fri, 15 Dec 2017, Michal Hocko wrote:

> > This uses the new annotation to determine if an mm has mmu notifiers with
> > blockable invalidate range callbacks to avoid oom reaping.  Otherwise, the
> > callbacks are used around unmap_page_range().
> 
> Do you have any example where this helped? KVM guest oom killed I guess?
> 

KVM is the most significant one that we are interested in, but haven't had 
sufficient time to quantify how much of an impact this has other than to 
say it will certainly be non-zero.

The motivation was more to exclude mmu notifiers that have a reason to be 
excluded rather than a blanket exemption to make the oom reaper more 
robust.