linux-kernel - Re: [patch 1/2] oom: remove oom_disable

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Message-ID: <alpine.DEB.2.00.1108301503510.2730@chino.kir.corp.google.com>
Date:	Tue, 30 Aug 2011 15:06:51 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ying Han <yinghan@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch 1/2] oom: remove oom_disable_count

On Tue, 30 Aug 2011, Oleg Nesterov wrote:

> > @@ -447,6 +431,9 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
> >  	for_each_process(q)
> >  		if (q->mm == mm && !same_thread_group(q, p) &&
> >  		    !(q->flags & PF_KTHREAD)) {
> 
> (I guess this is on top of -mm patch)
> 

Yes, it's based on 
oom-avoid-killing-kthreads-if-they-assume-the-oom-killed-threads-mm.patch 
which I thought would be pushed for the 3.1 rc series, we certainly don't 
want to SIGKILL kthreads :)

> > +			if (q->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
> > +				continue;
> > +
> 
> Afaics, this is the only change apart from "removes mm->oom_disable_count
> entirely", looks reasonable to me.
> 

Yeah, it's necessary because this loop in oom_kill_task() kills all 
user threads in different thread groups unconditionally if they share the 
same mm, so we need to ensure that we aren't sending a SIGKILL to anything 
that is actually oom disabled.  Before, the check in oom_badness() would 
have prevented the task (`p' in this function) from being chosen in the 
first place.
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