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Date: Mon, 14 May 2007 03:04:05 -0400
From: Kris Kennaway <kris@obsecurity.org>
To: Kevin Downey <redchin@gmail.com>
Message-ID: <20070514070405.GA70600@xor.obsecurity.org>
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Cc: "freebsd-questions@freebsd.org List" <freebsd-questions@freebsd.org>
Subject: Re: mdconfig -t malloc limits
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On Sun, May 13, 2007 at 09:34:46PM -0700, Kevin Downey wrote:
> I am building a shiny new desktop, the only thing I don't have right
> now is the hard drive, so
> I have been booting a minimal system off a flash drive. The box has
> two gigs of ram. if I try to create a malloc backed md device bigger
> then 300mb(this is not the exact limit but it is between 300mb and
> 400mb) it fails. If I use -o reserve the mdconfig command fails and if
> I don't then when I try and use that space FreeBSD crashes. It seems
> like there should be enough unused memory to create a 1gb malloc
> backed md.
> 
> I have no swap because the only drive is a flash drive.
> / is  mounted read only.
> /tmp and /var are 124mb malloc backed md devices
> 
> What is the deal? Is this some tunable limit? Should I fire up memtest?

See the manpage, or the archives for extensive discussion.  Bottom
line: you almost certain don't want to use malloc backing, but instead
swap backing.

Kris