mdconfig -t malloc limits

[Kevin Downey]

On 5/14/07, Kris Kennaway <kris at obsecurity.org> wrote:
> 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
>

using:
mdconfig -a -t swap -s 500m -o reserve
I get:
mdconfig: ioctl(/dev/mdctl): Numerical argument out of domain
in fact I get the same message no matter what size I pick.

I had assumed that since I don't have a swap partition setup that
using a backing method called 'swap' wasn't a good idea.

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