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Date: Thu, 12 Apr 2007 23:09:44 +0200
From: Willy Tarreau <w@1wt.eu>
To: "Mouawad, Tony" <Tony.Mouawad@christiedigital.com>
Cc: Pedro <linux_user@izecksohn.com>, linux-kernel@vger.kernel.org
Subject: Re: tmpfs and the OOM killer
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References: <20070412203153.GJ943@1wt.eu> <AD98412A5373CC4AA643D9C021922A541C4DE0@cdskitexg01.cds.int>
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On Thu, Apr 12, 2007 at 04:56:24PM -0400, Mouawad, Tony wrote:
> I have noticed that with overcommit_memory=2 and overcommit_ratio=100,
> my system cannot leverage as much ram as it could if it was configured
> for overcommit_memory=0.
> 
> Is this because when overcommit_memory=2, anything that mallocs memory
> but doesn't touch that memory is counted as used memory?

Most probably, yes. This proves that your system may endup doing OOM
in mode 0 if one of your applications suddenly decided to use all the
memory it has allocated.

> I see a value
> in /proc/meminfo called Commited_AS: and it seems to reflect what has
> been malloced in the system but not necessarily touched.  Is this true?

Yes (at least I do think so).

Regards,
Willy