Date: Sat, 22 Jan 2005 04:32:19 +0100
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
Message-ID: <20050122033219.GG11112@dualathlon.random>
References: <3f250c71050110134337c08ef0@mail.gmail.com> <20050110192012.GA18531@logos.cnet> <4d6522b9050110144017d0c075@mail.gmail.com> <20050110200514.GA18796@logos.cnet> <1105403747.17853.48.camel@tglx.tec.linutronix.de> <20050111083837.GE26799@dualathlon.random> <3f250c71050121132713a145e3@mail.gmail.com> <3f250c7105012113455e986ca8@mail.gmail.com>
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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.
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