linux-kernel - Re: can't oom-kill zap the victim's memory?

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Message-ID: <20151008140411.GC426@dhcp22.suse.cz>
Date:	Thu, 8 Oct 2015 16:04:11 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	torvalds@...ux-foundation.org, kwalker@...hat.com, cl@...ux.com,
	akpm@...ux-foundation.org, rientjes@...gle.com, hannes@...xchg.org,
	vdavydov@...allels.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, skozina@...hat.com
Subject: Re: can't oom-kill zap the victim's memory?

On Wed 07-10-15 14:00:16, Oleg Nesterov wrote:
> On 10/07, Tetsuo Handa wrote:
> >
> > Oleg Nesterov wrote:
> > > Anyway. Perhaps it makes sense to abort the for_each_vma() loop if
> > > freed_enough_mem() == T. But it is absolutely not clear to me how we
> > > should define this freed_enough_mem(), so I think we should do this
> > > later.
> >
> > Maybe
> >
> >   bool freed_enough_mem(void) { !atomic_read(&oom_victims); }
> >
> > if we change to call mark_oom_victim() on all threads which should be
> > killed as OOM victims.
> 
> Well, in this case
> 
> 	if (atomic_read(&mm->mm_users) == 1)
> 		break;
> 
> makes much more sense. Plus we do not need to change mark_oom_victim().
> 
> Lets discuss this later?

Yes I do not think this is that important if a kernel thread is going to
reclaim the address space. It will effectively free memory on behalf of
the victim so a longer scan shouldn't be such a big problem. At least
not for the first implementation.
-- 
Michal Hocko
SUSE Labs
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