linux-kernel - Re: [RFC][-mm][PATCH 4/6] oom-killer: fork bomb detector

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Message-Id: <20091102173912.601790b0.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 2 Nov 2009 17:39:12 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	aarcange@...hat.com, akpm@...ux-foundation.org,
	minchan.kim@...il.com, rientjes@...gle.com, vedran.furac@...il.com,
	"hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>
Subject: Re: [RFC][-mm][PATCH 4/6] oom-killer: fork bomb detector

On Mon, 2 Nov 2009 16:27:16 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> -
> -	/* Try to kill a child first */
> +	if (fork_bomb) {
> +		printk(KERN_ERR "possible fork-bomb is detected. kill them\n");
> +		/* We need to kill the youngest one, at least */
> +		rcu_read_lock();
> +		for_each_process_reverse(c) {
> +			if (c == p)
> +				break;
> +			if (is_forkbomb_family(c, p)) {
> +				oom_kill_task(c);
> +				break;
> +			}
> +		}
> +		rcu_read_unlock();
> +	}

Kosaki said we should kill all under tree and "break" is unnecessay here.
I nearly agree with him..after some experiments.

But it seems the biggest problem is latecy by swap-out...before deciding OOM
....

Thanks,
-Kame

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