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Date: Thu, 12 Sep 2002 12:30:53 -0600 (MDT)
From: Thunder from the hill <thunder@lightweight.ods.org>
X-X-Sender: thunder@hawkeye.luckynet.adm
To: Giuliano Pochini <pochini@shiny.it>
cc: Jim Sibley <jlsibley@us.ibm.com>, Troy Reed <tdreed@us.ibm.com>,
       <ltc@linux.ibm.com>, <riel@conectiva.com.br>,
       <linux-kernel@vger.kernel.org>
Subject: RE: Killing/balancing processes when overcommited
In-Reply-To: <XFMail.20020912092526.pochini@shiny.it>
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Hi,

On Thu, 12 Sep 2002, Giuliano Pochini wrote:
> It's not difficult to make the kerner choose the right processes
> to kill. It's impossible.

Not quite. But it's expensive. It adds 4 bytes per task, plus a second 
OOM killer.

> Imagine that when it goes oom the system stops and asks you what
> processes have to be killed. What do you kill ?

Rather whom would you ask?

> Probably we do need an oomd that the sysadmin can configure as he likes.

That's bad, it could get killed. ;-)

Mostly the mem eaters are those who hang in an malloc() deadloop.

	char *x = NULL;

	/*
	 * We need this variable, so if we don't get it, we reallocate it 
	 * regardless of what happened.
	 */
	do {
		x = malloc(X_SIZE);
	} while (!x);

That's possibly a candidate.

So if we just count how often per second that stubborn process uses 
malloc(), you'll catch the right guy most of the time. If you don't get 
a process that's over the threshold, do usual OOM killing...

			Thunder
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