linux-kernel - Re: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support

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Date:	Wed, 1 Jul 2009 01:07:43 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, tj@...nel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-arch@...r.kernel.org, andi@...stfloor.org, hpa@...or.com,
	tglx@...utronix.de
Subject: Re: [PATCHSET] percpu: generalize first chunk allocators and
	improve lpage NUMA support


* Christoph Lameter <cl@...ux-foundation.org> wrote:

> On Wed, 1 Jul 2009, Ingo Molnar wrote:
> 
> > The usecase i'm talking about is to boot a generic, 
> > many-CPUs-capable kernel in a guest image.
> 
> The many-cpu-capable kernel is not the issue. The number of 
> potential cpus is config information provided by the hardware. In 
> your case the host system provides the number of possible 
> processors.

Say it says "256 CPUs".

But i only run a 2 CPU guest system. But i want to run it with the 
_on demand capability_ to scale up to 256 virtual CPUs if needed, 
without having to reboot the guest and without having to allocate 
all the percpu space for 256 CPUs beforehand. Ok?

It is a simple, basic OS feature and concept.

	Ingo
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