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

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Date:	Tue, 30 Jun 2009 21:15:17 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Christoph Lameter <cl@...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


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 29 Jun 2009 19:20:53 -0400 (EDT)
> Christoph Lameter <cl@...ux-foundation.org> wrote:
> 
> > On Wed, 24 Jun 2009, Andrew Morton wrote:
> > 
> > > I assume from the tremendous number of 
> > > for_each_possible_cpu()s that CPU hotplug awareness won't be 
> > > happening.
> > 
> > Per cpu areas are allocated for all possible processors. No need 
> > to handle offlining and onlining them.
> 
> Well yes.  My point is that this is a bug-not-a-feature ;)

Yeah, it's a bug for something like a virtual environment which 
boots generic kernels that might have 64 possible CPUs (on a true 
64-way system), but which will have fewer in practice.

It's pretty basic stuff: the on-demand allocation of percpu 
resources.

	Ingo
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