Re: User space out of memory approach

From: Andrea Arcangeli <andrea@suse.de>
To: Mauricio Lin <mauriciolin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Marcelo Tosatti <marcelo.tosatti@cyclades.com>,
	Edjard Souza Mota <edjard@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>
Subject: Re: User space out of memory approach
Date: Sat, 22 Jan 2005 04:32:19 +0100	[thread overview]
Message-ID: <20050122033219.GG11112@dualathlon.random> (raw)
In-Reply-To: <3f250c7105012113455e986ca8@mail.gmail.com>

On Fri, Jan 21, 2005 at 05:45:13PM -0400, Mauricio Lin wrote:
> Hi Andrew,
> 
> I have another question. You included an oom_adj entry in /proc for
> each process. This was the approach you used in order to allow someone
> or something to interfere the ranking algorithm from userland, right?
> So if i have an another ranking algorithm in user space, I can use it
> to complement the kernel decision as necessary. Was it your idea?

Yes, you should use your userspace algorithm to tune the oom killer via
the oom_adj and you can check the effect of your changes with oom_score.
I posted a one liner ugly script to do that a few days ago on l-k.

The oom_adj has this effect on the badness() code:

	/* 
	 * Adjust the score by oomkilladj.
	 */
	if (p->oomkilladj) {
		if (p->oomkilladj > 0)
			points <<= p->oomkilladj;
		else
			points >>= -(p->oomkilladj);
	}

The biggest the points become, the more likely the task will be choosen
by the oom killer.