From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Date: Wed, 23 Sep 2009 22:03:00 +0000
Subject: Re: [PATCH 2/4] ia64: allocate percpu area for cpu0 like percpu areas
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List-Id: <linux-ia64.vger.kernel.org>
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To: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>, Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>, linux-ia64 <linux-ia64@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>, Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org

Christoph Lameter wrote:
> On Wed, 23 Sep 2009, Tejun Heo wrote:
> 
>> any special handling.  What problems are you seeing?
> 
> per cpu variable access on IA64 does not use the percpu_offset for the
> calculation of the current per cpu data area. Its using a virtual mapping.
> 
> How does the new percpu allocator support this? Does it use different
> methods of access for static and dynamic percpu access?

That's only when __ia64_per_cpu_var() macro is used in arch code which
always references static perpcu variable in the kernel image which
falls inside PERCPU_PAGE_SIZE.  For everything else, __my_cpu_offset
is defined as __ia64_per_cpu_var(local_per_cpu_offset) and regular
pointer offsetting is used.

Thanks.

-- 
tejun