linux-kernel - shared memory is over-counted N times when calculating badness()

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Message-Id: <1171318084.10824.113.camel@dogma.v10.wvs>
Date:	Mon, 12 Feb 2007 14:08:04 -0800
From:	Jeff Davis <linux@...avis.com>
To:	linux-kernel@...r.kernel.org
Subject: shared memory is over-counted N times when calculating badness()

In oom_kill.c, badness() counts half the total_vm of all the children
against the parent.

The problem with this calculation is that, if the parent and children
share memory, the shared memory is over-counted N/2 times where N is the
number of children.

There's already a hard limit on the amount of shared memory, so it's
unlikely that process is runaway due to shared memory consumption, and
shouldn't add to a process's badness() score.

Shouldn't it just use (total_vm - shared_vm) instead, and never even
count shared memory?

Regards,
	Jeff Davis

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