vm_thread_new: kstack allocation failed with vm.kmem_size="1536M"

[Alan Cox]

On Sun, Mar 1, 2009 at 8:57 AM, Pete French <petefrench at ticketswitch.com>wrote:

> > I'm running 7-STABLE as of Feb 26 or so.  Commit r187466 on Jan 20 bumped
> up
> > kmem_size_max on amd64 to 3.6GB:
> >
> > http://svn.freebsd.org/viewvc/base?view=revision&revision=187466
>
> Mmmmm.... now I am wworried about upgrading to STABLE! ;) I can't
> think of a reason why I am seeing what I am seeing - on 7.1-RELEASE
> I am certainly icreasing the limits not decreasing them, yet I
> am seeing it running out of memory on the larger limit.
>
> Note that these machines have no swap - but then since the system runs fine
> on a 4gig machine with 4 gig of sap, I made the assumption that if
> the machine was expanded to 8 gig of real memory it no longer needs the
> swap, as it now has as much real RAM in it as real+swap was before.
>
> -pete.
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When you adjust the kmem size, you are playing a zero-sum game.  When you
increase the kmem size, the additional space for the kernel's heap has to
come from somewhere.  One effect is that the available space for kernel
thread stacks is reduced.

If you're going to adjust kmem size, you should keep an eye on "sysctl
vm.kvm_free".

Regards,
Alan