Date: Tue, 30 Jun 2009 10:24:46 -0400 (EDT)
From: Christoph Lameter <cl@linux-foundation.org>
To: Andrew Morton <akpm@linux-foundation.org>
cc: tj@kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org,
       linux-arch@vger.kernel.org, mingo@elte.hu, andi@firstfloor.org,
       hpa@zytor.com, tglx@linutronix.de
Subject: Re: [PATCHSET] percpu: generalize first chunk allocators and improve
 lpage NUMA support
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On Mon, 29 Jun 2009, Andrew Morton wrote:

> On Mon, 29 Jun 2009 19:20:53 -0400 (EDT)
> Christoph Lameter <cl@linux-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 ;)

Its a feature that I would like to exploit in the future to get rid of
some of the hotplug callbacks in the allocator.

Some state also needs to be kept for offlined processors. This is done in
per cpu data.

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