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Message-ID: <alpine.DEB.1.10.0909230941560.21821@V090114053VZO-1>
Date: Wed, 23 Sep 2009 09:44:33 -0400 (EDT)
From: Christoph Lameter <cl@...ux-foundation.org>
To: Tejun Heo <tj@...nel.org>
cc: Nick Piggin <npiggin@...e.de>, Tony Luck <tony.luck@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
linux-ia64 <linux-ia64@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Rusty Russell <rusty@...tcorp.com.au>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] ia64: allocate percpu area for cpu0 like percpu
areas for other cpus
On Wed, 23 Sep 2009, Tejun Heo wrote:
> On ia64, the first chunk is fixed at PERCPU_PAGE_SIZE. It's something
> hardwired into the page fault logic and the linker script. Build will
> fail if the static + reserved area goes over PERCPU_PAGE_SIZE and in
> that case ia64 will need to update the special case page fault logic
> and increase PERCPU_PAGE_SIZE. The area reserved above is interim
> per-cpu area for cpu0 which is used between head.S and proper percpu
> area setup and will be ditched once initialization is complete.
You did not answer my question.
The local percpu variables are accessed via a static per cpu
virtual mapping. You cannot place per cpu variables outside of that
virtual address range of PERCPU_PAGE_SIZE.
What happens if the percpu allocator allocates more data than available in
the reserved area?
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