linux-kernel - Re: x86: Convert cpu_core_map to be a per cpu variable

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Date:	Tue, 17 Jul 2007 12:27:18 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Christoph Lameter <clameter@....com>
Cc:	ak@...e.de, linux-kernel@...r.kernel.org, travis@....com,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: x86: Convert cpu_core_map to be a per cpu variable

On Thu, Jul 12, 2007 at 11:58:06PM -0700, Christoph Lameter wrote:
> cpu_core_map is currently an array defined using NR_CPUS. This means that
> we overallocate since we will rarely really use the maximum 
> number of configured cpus. This may become a problem when we need to 
> increase the NR_CPUs on x86_64 for our new product line.
> 
> If we put the cpu_core_map into the per cpu area then it will be allocated
> for each processor as it comes online.
> 
> However, this means that the core map cannot be accessed until the per cpu 
> area has been allocated. Xen does a weird thing here looping over all 
> processors and zeroing the masks that are not yet allocated and that will 
> be zeroed when they are allocated. I commented the code out. Maybe there 
> is another purpose? Jeremy?

Is there a reason why cpu_sibling_map[] is left out in these changes?

thanks,
suresh
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