linux-kernel - Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init

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Message-ID: <20160615143701.GA7944@redhat.com>
Date:	Wed, 15 Jun 2016 16:37:01 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	linux-mm@...ck.org,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	David Rientjes <rientjes@...gle.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or
 global init

Michal,

I am going to ack the whole series, but send some nits/questions,

On 06/09, Michal Hocko wrote:
>
> @@ -283,10 +283,22 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
>  
>  	/*
>  	 * This task already has access to memory reserves and is being killed.
> -	 * Don't allow any other task to have access to the reserves.
> +	 * Don't allow any other task to have access to the reserves unless
> +	 * the task has MMF_OOM_REAPED because chances that it would release
> +	 * any memory is quite low.
>  	 */
> -	if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims))
> -		return OOM_SCAN_ABORT;
> +	if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) {
> +		struct task_struct *p = find_lock_task_mm(task);
> +		enum oom_scan_t ret = OOM_SCAN_ABORT;
> +
> +		if (p) {
> +			if (test_bit(MMF_OOM_REAPED, &p->mm->flags))
> +				ret = OOM_SCAN_CONTINUE;
> +			task_unlock(p);

OK, but perhaps it would be beter to change oom_badness() to return zero if
MMF_OOM_REAPED is set?

Oleg.