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SubjectRe: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support
On Thu, Jun 25, 2009 at 07:18:07AM -0700, H. Peter Anvin wrote:
> Andi Kleen wrote:
> >>>
> >> *Ahem* virtual machines *ahem*...
> >
> > And? Even there's not that big typically.
> >
> > The traditional problem was just for 128 NR_CPUs kernel were nothing
> > was sized based on machine capacity.
> >
> > Also on large systems the VMs shouldn't be sized for full capacity.
> >
>
> We have already have cases where the "possible" CPUs have eaten up the
> entire vmalloc area on 32 bits. In real use. It's a real problem.

That's hard to believe or a serious bug/misconfiguration somewhere.

Each per CPU data should be <100k (let's say 200k with some slack for modules),
so to fill vmalloc you would need hundreds of CPUs, which a 32bit
kernel doesn't really support anyways because it doesn't support
enough memory for that many CPUs.

Perhaps you had firmware/hypervisor who passed a gigantic impossible
value here? If yes thy

-Andi

--
ak@linux.intel.com -- Speaking for myself only.


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