linux-kernel - Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers

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Date:   Mon, 23 Jul 2018 10:43:36 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Sudeep Dutt <sudeep.dutt@...el.com>,
        Ashutosh Dixit <ashutosh.dixit@...el.com>,
        Dimitri Sivanich <sivanich@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Felix Kuehling <felix.kuehling@....com>, kvm@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Christian König <christian.koenig@....com>,
        David Rientjes <rientjes@...gle.com>,
        Leon Romanovsky <leonro@...lanox.com>
Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers

On Fri 20-07-18 16:01:25, Andrew Morton wrote:
> On Tue, 17 Jul 2018 10:12:01 +0200 Michal Hocko <mhocko@...nel.org> wrote:
> 
> > > Any suggestions regarding how the driver developers can test this code
> > > path?  I don't think we presently have a way to fake an oom-killing
> > > event?  Perhaps we should add such a thing, given the problems we're
> > > having with that feature.
> > 
> > The simplest way is to wrap an userspace code which uses these notifiers
> > into a memcg and set the hard limit to hit the oom. This can be done
> > e.g. after the test faults in all the mmu notifier managed memory and
> > set the hard limit to something really small. Then we are looking for a
> > proper process tear down.
> 
> Chances are, some of the intended audience don't know how to do this
> and will either have to hunt down a lot of documentation or will just
> not test it.  But we want them to test it, so a little worked step-by-step
> example would help things along please.

I am willing to give more specific steps. Is anybody interested? From my
experience so far this is not something drivers developers using mmu
notifiers would be unfamiliar with.

-- 
Michal Hocko
SUSE Labs