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Date:   Mon, 23 Jul 2018 10:43:36 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
        "David (ChunMing) Zhou" <David1.Zhou@amd.com>,
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Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers
Message-ID: <20180723084336.GH17905@dhcp22.suse.cz>
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On Fri 20-07-18 16:01:25, Andrew Morton wrote:
> On Tue, 17 Jul 2018 10:12:01 +0200 Michal Hocko <mhocko@kernel.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