linux-kernel - Re: [PATCH 2/4] ia64: allocate percpu area for cpu0 like percpu areas for other cpus

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Message-ID: <4ABA2A3A.6020308@kernel.org>
Date:	Wed, 23 Sep 2009 23:01:30 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux-foundation.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

Hello,

Christoph Lameter wrote:
> You did not answer my question.

Hmmm...

> 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?

I still don't understand your question.  Static percpu variables are
always allocated from the first chunk inside that PERCPU_PAGE_SIZE
area.  Dynamic allocations can go outside of that but they don't need
any special handling.  What problems are you seeing?

-- 
tejun
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